Patent Publication Number: US-7591546-B2

Title: Tank unit, ink jet recording head and method of manufacturing tank unit and ink jet recording head

Description:
This application is a division of application Ser. No. 10/918,441, filed Aug. 16, 2004, the contents of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invent relates to an ink jet recording head of an ink jet recording apparatus that performs recording by discharging inks. 
   2. Description of the Related Art 
     FIG. 17  shows an exploded perspective view for explaining a construction of a conventional ink jet recording head.  FIG. 18  shows a cross sectional view of a recording head cartridge in which an ink tank is installed in the ink jet recording head.  FIGS. 19A through 19C  show schematic sectional enlarged views for explaining a step of forming an ink flow path. 
   An ink jet recording head  1020  shown in  FIGS. 17 and 18  has hitherto used a method of assembling a tank holder unit  1200  by ultrasonic-wave-welding an flow path forming member  1220  to a tank holder  1210  in order to form an ink flow path  1214  for guiding an ink in an ink tank  1040  to a recording element unit  1300  via the tank holder  1201 . 
   As shown in  FIG. 18 , in a state where the ink tank  1040  is installed in the ink jet recording head  1020 , the ink is supplied into the ink jet recording head  1020  via a joint portion including a filter  1230  and a seal rubber  1240  from an ink supply port  1401  of the ink tank  1040 . The ink is supplied to a recording element substrate  1330  of the recording element unit  1300  via the ink flow path  1214 , and is then discharged onto a recording sheet (unillustrated) by dint of energy generated by energy elements (unillustrated) within a silicon substrate. 
   At this time, the ink flow path  1224  is formed by connecting the flow path forming member  1220  to the tank holder  1210  by the ultrasonic wave welding. To explain an assembling step with reference to  FIGS. 19A through 19C , the tank holder  1210  is, as shown in  FIG. 19A , formed with a groove serving as a burr reservoir  1218  in a connecting portion, while the flow path forming member  1220  is formed with a welding rib  1227  on the connecting portion. As shown in  FIG. 19B , the flow path forming member  1220  is placed on the tank holder so that the welding rib  1227  is fitted into the groove of the burr reservoir  1218 . Further, the flow path forming member  1220  is pressed from above by an ultrasonic wave welding horn  1054 , and ultrasonic waves are oscillated while applying a pressure. With the oscillations, as shown in  FIG. 19C , the welding rib  1227  spreads in the burr reservoir  1218  while being melted, and the tank holder  1210  and the flow path forming member  1220  are thus firmly connected together, thereby forming the ink flow path  1224 . 
   Note that the numeral  1310  represents a first plate,  1311  designates an ink supply port formed in the first plate,  1320  denotes a second plate,  1330  stands for a recording element substrate,  1337  represents a discharge port formed in the recording element substrate,  1340  indicates an electric wiring board, and  1341  designates an external signal input terminal for electrically connecting the ink jet recording head to the ink jet recording apparatus in  FIGS. 17 and 18 . The first plate  1311  is connected to the flow path forming member  1220  and supports the recording element substrate  1330  and the second plate  1320  as well. The second plate  1320  supports the electric wiring board  1340 . These members constitute the recording element unit  1300 . 
   SUMMARY OF THE INVENTION 
   The method described so far is a rational method as a means for surely forming an airtight ink flow path in a short period of time at a low cost. In the prior art described above, however, the burrs melted out of the welding rib  1227  by the oscillations of the ultrasonic waves bulge over the ink flow path  1224  from the burr reservoir  12218 , with the result that fine resinous grains are fragmented into pieces of dusts and clog in the ink discharge port  1337  of the recording element substrate  1330 . This results in a discharge defect of the ink and might cause a decline of reliability on the ink jet recording head  1020 . 
   For eliminating the dusts produced by the resin burrs, the ink flow path  1224  is washed in a subsequent washing step. The burr reservoir  1218  is not, however, all filled with the welded burrs, and a slight gap is left and becomes a stagnated portion when flowing the wash water. Then, a washing pressure of the wash water is hard to be exerted, and a considerably long period of time is required for completely flowing the dusts away. This makes it impossible to reduce assembly time and is a factor for raising the costs. 
   Moreover, the flow path forming member  1220  is provided with a protruded portion of the ultrasonic wave welding rib  1227 , and the tank holder  1201  is formed with the recessed portion as the burr reservoir  1218 . Therefore, a gap between the adjacent ink flow paths must be set equal to or larger than approximately 1.5 mm. As a result, there arises such inconvenience that the ink flow paths can not be disposed at a high density, and hence it is difficult to downsize the ink jet recording head. 
   On the other hand, Japanese Patent Application Laid-Open Publication No. 8-183182 and U.S. Pat. No. 5,808,641 disclose technologies, wherein a resinous top board having a plurality of discharge ports and a plurality of liquid flow paths and a substrate for generating discharge energy, are integrally welded by irradiation of the laser beams. These technologies prevent such inconvenience that liquid discharge performance is declined by a distortion caused on the resinous top board and by resultant deformations of the liquid flow paths and the discharge ports as happened in the conventional method for making the resinous top board and the substrate integral by pressing the resinous top board against the substrate through an elastic member. 
   The sure welding of this resinous top board to the substrate, however, involves providing a resinous film on a welding surface on the substrate beforehand, and a resinous film adhering step therefor is incorporated into the substrate manufacturing step. This leads to an increase in the cost for the substrate. 
   It is an object of the present invention to provide an ink jet recording head, wherein a connection between a tank holder (which will hereinafter also be called a “container holding member) for forming an ink flow path (which will hereinafter referred to also as a “liquid flow path”) and a flow path forming member, is conducted surely in a small number of steps at a short interval between flow paths without producing foreign matters within the ink flow path. 
   According to one aspect of the present invention, an ink jet recording head comprises a container holding member to which a liquid accommodating container for accommodating a liquid is attached, and a flow path forming member connected to the container holding member, and a plurality of liquid flow paths linked to the liquid accommodation container are formed between the container holding member and the flow path forming member that have been connected together. Further, at least one of the container holding member and the flow path forming member is formed with a recessed portion for forming the liquid flow path, at least one of a junction surface portion of the container holding member and a junction surface portion of the flow path forming member has a protruded portion assuming a protruded shape from non-connected surfaces of the members having the junction surface portions. Moreover, the flow path forming member is composed of a resin exhibiting transmissivity of laser beam, a non-transmissive material exhibiting none of transmissivity of the laser beam exists in at least a junction area of the container holding member between the container holding member and the flow path forming member, the non-transmissive material emits heat by irradiating a periphery of the ink flow path with the laser beam from the side of the flow path forming member in a state where the flow path forming member is pressure-welded to the container holding member, and the junction surface portion of the container holding member and the junction surface portion of the flow path forming member are welded, thereby forming the liquid flow path. 
   According to another aspect of the present invention, there is provided a method of manufacturing an ink jet recording head comprising a container holding member to which a liquid accommodating container for accommodating a liquid is attached, and a flow path forming member connected to the container holding member, wherein a plurality of liquid flow paths communicating with the liquid accommodation container are formed between the container holding member and the flow path forming member that have been connected together. The ink jet recording head manufacturing method comprises a preparing step of the container holding member and the flow path forming member, in which at least one of the container holding member and the flow path forming member is formed with a recessed portion for forming the liquid flow path, at least one of a junction surface portion of the container holding member and a junction surface portion of the flow path forming member has a protruded portion assuming a protruded shape from non-connected surfaces of the members having the junction surface portions, a press-connecting step of press-connecting the container holding member and the flow path forming member in a state where a non-transmissive material exhibiting none of transmissivity of the laser beam exists in at least a junction area between the container holding member and the flow path forming member, and a welding step of irradiating a periphery of the ink flow path with the laser beam from the side of the flow path forming member composed of a resin having transmissivity of the laser beam in a state where the flow path forming member and the container holding member are press-connected to each other, thus heating the non-transmissive material, then welding the junction surface portion of the container holding member and the junction surface portion of the flow path forming member by this heating, and thus forming the liquid flow path. 
   At least one surface of the junction surfaces in the periphery of the portions formed with the liquid flow paths of the container holding member and of the flow path forming member, is formed in the protruded shape from the non-junction surfaces. The flow path forming member is composed of the transparent resin having the transmissivity of the laser beam. The non-transmissive material having no transmissivity of the laser beam exists in at least the junction surface area of the container holding member. In the state where the flow path forming member is press-connected to the container holding member, the junction surface is welded by irradiating the periphery of the liquid flow path with the laser beam from the side of the flow path forming member, thereby forming the liquid flow path. The method, which is simple and attained at a low cost, provides the ink jet recording head capable of designing a high-density layout of the liquid flow paths with neither occurrence of the dusts of the resinous materials composing the container holding member and the flow path forming member nor formation of the stagnated portion within the liquid flow path. 
   As described above, the present invention yields an effect that the method, which is simple and attained at the low cost, enables the formation of the ink jet recording head capable of designing the high-density layout of the liquid flow paths with neither the occurrence of the dusts of the resinous materials composing the container holding member and the flow path forming member nor formation of the stagnated portion within the ink flow path. 
   The following is the reason for this. At least one surface of the junction surfaces in the periphery of the portions formed with the liquid flow paths of the tank holder and of the flow path forming member, is formed in the protruded state from the non-junction surfaces. The flow path forming member is composed of the transparent resin having the transmissivity of the laser beam. The non-transmissive material having no transmissivity of the laser beam exists in at least the junction surface area of the tank holder. In the state where the flow path forming member is press-connected to the tank holder, the junction surface portions of the tank holder and of the flow path forming member are welded by irradiating the periphery of the ink flow path with the laser beam from the side of the flow path forming member, thereby forming the liquid flow path. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic perspective view showing a step of attaching a flow path forming member to a tank holder of an ink jet recording head in a first embodiment of the present invention; 
       FIG. 2  is a schematic perspective view showing a step of irradiating, with laser beams, the flow path forming member attached to the tank holder of the ink jet recording head in the first embodiment of the present invention; 
       FIGS. 3A and 3B  are schematic side sectional views of  FIGS. 1 and 2 ;  FIG. 3A  corresponds to  FIG. 1 ;  FIG. 3B  corresponds to  FIG. 2 ; 
       FIGS. 4A ,  4 B and  4 C are schematic side surface partial sectional views showing a step of bonding the flow path forming member to the tank holder of the ink jet recording head in the first embodiment of the present invention;  FIG. 4A  shows a relative relationship between the tank holder and the flow path forming member before being bonded;  FIG. 4B  shows a state of irradiating the flow path forming member with the laser beams in a way that abuts the flow path forming member on the tank holder;  FIG. 4C  shows a bonded state; 
       FIGS. 5A and 5B  are perspective views of a recording head cartridge;  FIG. 5A  shows an assembled state;  FIG. 5B  shows a state where the ink tanks are removed; 
       FIG. 6  is a perspective view of a tank holder unit and a recording element unit of the ink jet recording head; 
       FIG. 7  is a schematic exploded perspective view of the ink jet recording head; 
       FIG. 8  is a schematic partially cut perspective view of a recording element substrate constituting a recording element unit; 
       FIG. 9  is a schematic perspective view showing a relationship between the ink jet recording head and the ink tanks; 
       FIG. 10  is a schematic sectional view of the recording head cartridge; 
       FIGS. 11A ,  11 B and  11 C are schematic side surface partial sectional views showing a step of connecting the flow path forming member to the tank holder of the ink jet recording head in a second embodiment of the present invention;  FIG. 11A  shows a relative relationship between the tank holder and the flow path forming member before the connection;  FIG. 11B  shows a state in which the flow path forming member is irradiated with the laser beam in a way that abuts the flow path forming member on the tank holder;  FIG. 11C  shows a connected state; 
       FIGS. 12A ,  12 B and  12 C are schematic side surface partial sectional views showing a step of connecting the flow path forming member to the tank holder of the ink jet recording head in a third embodiment of the present invention;  FIG. 12A  shows a relative relationship between the tank holder and the flow path forming member before the connection;  FIG. 12B  shows a state in which the flow path forming member is irradiated with the laser beam in a way that abuts the flow path forming member on the tank holder;  FIG. 12C  shows a connected state; 
       FIG. 13A  is a sectional photo of an ink flow path when cut in a direction vertical to a direction in which a liquid flows within the ink flow path formed by utilizing conventional ultrasonic wave welding;  FIG. 13B  is a sectional photo of the ink flow path when cut in a direction vertical to the direction in which the liquid flows within the ink flow path formed by utilizing laser welding in the present embodiment; 
       FIG. 14  shows a conceptual diagram of an in-liquid particle measuring apparatus; 
       FIGS. 15A ,  15 B and  15 C are schematic side surface partial sectional views showing a step of connecting the flow path forming member to the tank holder of the ink jet recording head in a fourth embodiment of the present invention;  FIG. 15A  shows a relative relationship between the tank holder and the flow path forming member before the connection;  FIG. 15B  shows a state in which the flow path forming member is irradiated with the laser beam in a way that abuts the flow path forming member on the tank holder;  FIG. 15C  shows a connected state; 
       FIGS. 16A ,  16 B and  16 C are schematic side surface partial sectional views showing a step of connecting the flow path forming member to the tank holder of the ink jet recording head in a fifth embodiment of the present invention;  FIG. 16A  shows a relative relationship between the tank holder and the flow path forming member before the connection;  FIG. 16B  shows a state in which the flow path forming member is irradiated with the laser beam in a way that abuts the flow path forming member on the tank holder;  FIG. 16C  shows a connected state; 
       FIG. 17  is an exploded perspective view for explaining a construction of an ink jet recording head in the prior art; 
       FIG. 18  is a cross sectional view of a recording head cartridge in which an ink tank is installed in the ink jet recording head in the prior art; and 
       FIGS. 19A ,  19 B and  19 C are schematic side surface partial sectional views showing a step of connecting the flow path forming member to the tank holder of the ink jet recording head in the prior art;  FIG. 19A  shows a relative relationship between the tank holder and the flow path forming member before the connection;  FIG. 19B  shows a state in which an ultrasonic wave welding horn is oscillated in such a way that the flow path forming member is made contiguous to the tank holder and is pressed from above by the ultrasonic wave welding horn;  FIG. 19C  shows a connected state. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention will be described in detail with reference to the drawings.  FIG. 1  is a perspective view showing a step of attaching a flow path forming member to a tank holder of an ink jet recording head in a first embodiment of the present invention.  FIG. 2  is a schematic perspective view showing a step of irradiating, with laser beams, the flow path forming member attached to the tank holder of the ink jet recording head in the first embodiment of the present invention.  FIGS. 3A and 3B  are schematic side views of  FIGS. 1 and 2 .  FIG. 3A  corresponds to  FIG. 1 , while  FIG. 3B  corresponds to  FIG. 2 .  FIGS. 4A ,  4 B and  4 C are schematic sectional views of side surfaces, showing a step of bonding the flow path forming member to the tank holder of the ink jet recording head in the first embodiment of the present invention.  FIG. 4A  shows a relative relationship between the tank holder and the flow path forming member before being bonded.  FIG. 4B  shows a state of irradiating the flow path forming member with the laser beams in a way that abuts the flow path forming member on the tank holder.  FIG. 4C  shows a bonded state. 
   The discussion will start with explaining a construction of the ink jet recording head in the first embodiment of the present invention and a relationship between related pieces of components such as a recording head cartridge, ink tanks, an ink jet recording apparatus body and a carriage.  FIGS. 5 through 9  are explanatory views therefor.  FIGS. 5A and 5B  are perspective views of the recording head cartridge.  FIG. 5A  shows an assembled state.  FIG. 5B  shows a state where the ink tanks are removed.  FIG. 6  is a perspective view of a tank holder unit and a recording element unit of the ink jet recording head.  FIG. 7  is a schematic exploded perspective view of the ink jet recording head.  FIG. 8  is a schematic partially cut perspective view of a recording element substrate constituting the recording element unit.  FIG. 9  is a schematic perspective view showing a relationship between the ink jet recording head and the ink tanks. Configurations of the respective portions will hereinafter be explained with reference to the drawings. 
   An ink jet recording head  20  of the present invention is, as can be understood from the perspective views in  FIGS. 5A and 5B , one component configuring a recording head cartridge  10 . The recording head cartridge  10  is constructed of the ink jet recording head  20  and ink tanks  40  ( 41 ,  42 ,  43 ,  44 ,  45 ,  46 ) defined as liquid accommodation containers so provided as to be detachably attached to the ink jet recording head  20 . This recording head cartridge  10  is fixedly supported by a positioning means and an electric contact of the carriage mounted on the unillustrated ink jet recording apparatus body, and is detachable from and attachable to this carriage. The ink tank  41  is provided for containing a black ink. The ink tank  42  is for a light cyan ink. The ink tank  43  is for a light magenta ink. The ink tank  44  is for a cyan ink. The ink tank  45  is for a magenta ink. The ink tank  46  is for a yellow ink. Thus, the ink tanks  41 ,  42 ,  43 ,  44 ,  45  and  46  are each detachably attached to the ink jet recording head  20  and also replaceable. This construction leads to a decrease in print running costs in the ink jet recording apparatus. The recording head cartridge, the ink jet recording head, the ink tanks, the ink jet recording apparatus body and the carriage, which are shown in  FIGS. 5 through 9 , have configurations to which a variety of novel technologies established at a stage of accomplishing the present invention were applied, and hence the whole construction will be described in a way that briefly explains their configurations. 
   (1) Explanation of Inkjet Recording Head 
   The ink jet recording head  20  is an ink jet recording head classified as a side shooter type in a bubble jet system, wherein recording is conducted by use of an electro-thermal converting element for generating thermal energy for producing film boiling for the ink in accordance with an electric signal. 
   The ink jet recording head  20  is, as shown in the exploded perspective view in  FIG. 6 , constructed of a recording element unit  300  and a tank holder unit  200 . Further, as illustrated in the exploded perspective view in  FIG. 7 , the recording element unit  300  is constructed of a recording element substrate  330 , a first plate  310 , an electric wiring board  340  and a second plate  320 . Further, the tank holder unit  200  is constructed of a tank holder  210  serving as a contained holding member, a flow path forming member  220 , a filter  230  and a seal rubber  240 . 
   (1-1) Recording Element Unit 
     FIG. 8  is a perspective view with some portion cut off in order to illustrate a configuration of the recording element substrate  330 . In the recording element substrate  330 , a thin film (layer) is formed of a silicon substrate  331  that is, e.g., 0.5 mm to 1 mm in thickness. Moreover, there are formed six rows of ink supply ports  332  configured by elongate channel-like through-ports serving as flow paths for six color inks, and electro-thermal converting elements  333  are arrayed row by row in a cross pattern on both sides of each ink supply port  332 . The electro-thermal converting element  333  and an electric wire of Al, etc. for supplying the electro-thermal converting element  333  with electric power are formed by a film forming technology. Further, a bump  335  of Au, etc. is provided on an electrode portion  334  for supplying the electric wire with the electric power. Formation of the ink supply port  332  involves effecting anisotropic etching by utilizing crystal orientations of the silicon substrate  331 . If a crystal orientation &lt;100&gt; is given on a wafer surface and a crystal orientation &lt;111&gt; is given in a thicknesswise direction, etching at an angle of approximately 54.7 degree advances based on the anisotropic etching of alkaline series (KOH, TMAH, hydrazine, etc.). The etching to a desired depth is attained by utilizing this method. Further, an ink flow path wall  336  for forming the ink flow path corresponding to the electro-thermal converting element  333  and a discharge port  337  are formed by a photolithography technique in the silicon substrate  331 , and six discharge port trains  338  corresponding to the six color inks are formed. Moreover, the electro-thermal converting element  333  is provided facing the discharge port  337 , through which the ink supplied from the ink supply port  332  is discharged in such a way that the electro-thermal converting element  333  produces an air bubble. 
   The first plate  310  is composed of a material of, for instance, aluminum (Al 2 O 3 ) having a thickness of 0.5 mm to 10 mm. The material of the first plate  310  is not limited to alumina. The first plate  310  may be composed of a material exhibiting a linear expansion coefficient equal to a linear expansion coefficient of the material for the recording element substrate  330  and a thermal conductivity equal to or larger than a thermal conductivity of the material of the recording element substrate  330 . The material of the first plate  310  may be any one of, for example, silicon (Si), aluminum nitride (AlN), zirconium oxide (ZrO 2 ), silicon nitride (Si 3 N 4 ), silicon carbide (SiC), molybdenum (Mo) and tungsten (W). The first plate  310  is formed with six pieces of ink supply ports  311  for supplying the six color inks to the recording element substrate  330 . The six ink supply ports  332  of the recording element substrate  330  correspond respectively to six pieces ink supply ports  311  in the first plate  310 , and the recording element substrate  330  is fixedly bonded with a high positional accuracy to the first plate  310 . A first bonding agent used for bonding is coated substantially in a shape of the recording element substrate over the first plate  310  so that none of air paths are formed between the ink supply ports adjacent to each other. A desirable bonding agent as the first bonding agent is, for instance, low of its viscosity and thin of a bonding layer formed on a contact surface, and exhibits comparatively high hardness after being hardened and ink resistance as well. The first bonding agent is a thermosetting bonding agent composed mainly of, e.g., an epoxy resin, and it is desirable that a thickness of the bonding layer be equal to or smaller than 50 μm. 
   The electric wiring board  340  serves to apply a signal voltage for discharging the ink to the recording element substrate  330 . The electric wiring board  340  includes an aperture portion through which the recording element substrate  330  is built in, an electrode terminal (unillustrated) corresponding to the electrode portion  334  of the recording element substrate  330 , and an external signal input terminal  341  disposed at an end portion of this wire and serving to receive the electric signal from the body apparatus. The electric wiring board  340  and the recording element substrate  330  are electrically connected to each other. A connection method thereof is that, for example, after coating a thermosetting bonding resin over between the electrode portion  334  of the recording element substrate  330  and the electrode terminal of the electric wiring board  340 , the electrode portion  334  of the recording element substrate  330  and the electrode terminal of the electric wiring board  340  are batchwise heated and simultaneously pressurized by a heat tool, and the thermosetting bonding resin is thus hardened, whereby the electrode portion  334  and the electrode terminal are electrically batchwise connected. Further, in the case of using an anisotropic conductive bonding agent containing conductive particles, the thermosetting bonding resin is likewise available. The material of the electric wiring board  340  involves using, for instance, a flexible wiring board having a 2-layered wiring structure in which a surface layer is covered with a resist film. Moreover, a reinforcing plate is bonded to the back surface of the external signal input terminal  341 , thereby improving planarity of the portion of the external signal input terminal  341 . A material of the reinforcing plate involves the use of heat resistive materials such as glass epoxy, aluminum, etc. that are each 0.5 mm to 2 mm in plate thickness. 
   The second plate  320  is formed of a material of, for instance, aluminum (Al 2 O 3 ) having a thickness of 0.5 mm to 1 mm. It should be noted that the material of the second plate  320  is not limited to aluminum. The second plate  320  may be composed of a material exhibiting a linear expansion coefficient equal to a linear expansion coefficient of each of the materials for the recording element substrate  330  and the first plate  310  and also exhibiting a thermal conductivity equal to or larger than a thermal conductivity of each of the substrate  330  and the plate  310 . Then, the second plate  320  takes a configuration having an aperture portion larger than a dimension of an external configuration of the recording element substrate  330  fixedly bonded to the first plate  310 . Further, the recording element substrate  330  and the electric wiring board  340  are boned to the first plate  310  by a second bonding agent so that the substrate  330  and the board  340  can be electrically connected in plane, and the back surface of the electric wiring board  340  is fixedly bonded by a third bonding agent. Moreover, the electric wiring board  340 , which is bonded to the second plate  320 , is at the same time bent at one side surfaces of the first plate  310  and of the second plate  320  and thus bonded to the side surface of the first plate  310  by the third bonding agent. A bonding agent usable as the second bonding agent is, for instance, low of its viscosity and thin of a bonding layer formed on a contact surface, and exhibits ink resistance. Further, the third bonding agent involves using a thermosetting bonding film composed mainly of, e.g., an epoxy resin and having a thickness of 10 to 100 μm. 
   The electric connecting portions between the recording element substrate  330  and the electric wiring board  340  of the thus constructed recording element unit  300 , are sealed by a first sealing agent and a second sealing agent and thus protected from corrosion due to the inks and from an external impact. The first sealing agent seals mainly an outer peripheral portion of the recording element substrate  330 , while the second sealing agent seals an edge of the aperture portion of the electric wiring board  340 . Moreover, the bent electric wiring board  340  is further subjected to forming in accordance with a shape of the tank holder unit  200 . 
   (1-2) Tank Holder Unit 
   The tank holder  210  is formed by, e.g., molding of a resin. It is desirable to use, as this resinous material, a resinous material mixed with 5% to 40% of a glass filler in order to improve a configurational rigidity. The tank holder  210  holds the detachable/attachable ink tanks  40 , and has tank positioning pins, tank positioning holes, i.e., a first hole, a second hole and a third hole with which a first pawl, a second pawl and a third pawl are respectively engaged, and an aperture portion for a prism employed for detecting an ink residual amount. Further, the tank holder  210  includes an installation guide for guiding the recording head cartridge  10  to an installing position of the carriage of the ink jet recording apparatus body, an engagement portion for fixedly installing the recording head cartridge  10  into the carriage by use of s head set lever, and X-, Y- and Z-abutting portions for positioning in a predetermined installing position of the carriage. Moreover, the tank holder  210  has a terminal fixing portion for positioning and thus fixing the portion of the external signal input terminal  341  of the recording element unit  300 , a plurality of ribs are provided on the terminal fixing portion and along its periphery, thereby strengthening rigidity of the surface including the terminal fixing portion. Further, color-separation ribs for preventing the respective colors from being intermingled each other are provided in color-separation spaces in which the respective ink tanks  41 ,  42 ,  43 ,  45  and  46  are installed. Moreover, finger anti-slip portions are provided on the side surfaces of the tank holder  210 , thereby improving a handling property of the ink jet recording head  20 . Further, as shown in  FIG. 7 , the tank holder  210  is formed with an ink flow path  214  for guiding the ink to the recording element unit  300  from the ink tank  40 , wherein the ink flow path  214  is one component of the tank holder unit  200  and was, according to the prior art, formed by ultrasonic-welding the flow path forming member  220 . Furthermore, a filter  230  for preventing dusts from entering from outside is joined by thermal welding to a joint portion engaging with the ink tank  40 , and a seal rubber  240  for preventing evaporation of the ink from the joint portion is attached. 
   (1-3) Connection of Recording Element Unit and Tank Holder Unit 
   As shown in  FIG. 6 , the ink jet recording head  20  is completed by connecting the recording element unit  300  to the tank holder unit  200 . The connection is conducted in the following manner. A portion of the ink supply port (the ink supply port  311  of the first plate  310 ) of the recording element unit  300  and a portion of the ink supply port (the ink flow path  224  of the flow path forming member  220 ), are fixedly bonded by coating a fourth bonding agent over there so that these ink supply ports communicate with each other. Further, other than the portions of the ink supply ports, several portions at which the recording element unit  300  and the tank holder unit  200  abut on each other, are fixedly bonded by a fifth bonding agent. Desirable bonding agents as the fourth and fifth bonding agents exhibit the ink resistance, get hardened at a normal temperature and are flexible enough to withstand a linear expansion difference between different types of materials. According to the present embodiment, for example, a moisture absorption hardening type silicon bonding agent is used. Furthermore, the fourth bonding resin and the fifth bonding resin may be the same bonding agent. Moreover, when bonding the recording element unit  300  to the tank holder unit  200  with the fourth and fifth bonding agents, the recording element unit  300  is positioned and thus fixed by use of a sixth bonding agent. It is, desirable that the sixth bonding agent be instantaneously hardened. According to the present embodiment, for instance, an ultraviolet-ray hardening bonding agent is employed, however, other bonding agents may also be available. 
   A portion of the external signal input terminal  341  of the recording element unit  300  is positioned and thus fixed to one side surface of the tank holder  210  by use of terminal positioning pins (two pieces) and terminal positioning holes (two pieces). A fixing method is, for instance, such that a terminal connection pin provided on the tank holder  210  is fitted into a terminal connection hole provided in the periphery of the external signal input terminal  341  of the electric wiring board  340 , and the fixation is attained by terminally welding the terminal connection pin. Other fixing means may, however, be usable. 
   (2) Description of Recording Head Cartridge 
     FIG. 9  illustrates the way of installing the ink jet recording head  20  constituting the recording head cartridge  10  and the ink tanks  41 ,  42 ,  43 ,  44 ,  45 ,  46 . Referring to  FIG. 9 , the ink tanks  41 ,  42 ,  43 ,  44 ,  45 ,  46  contain the inks assuming the colors corresponding to the respective tanks. Further, the individual ink tanks  40  are formed with ink supply ports  401  for supplying the ink jet recording head  20  with the inks contained in the ink tanks. For example, the ink tank  41  is formed with the ink supply port  401  through which the black ink in the ink tank  41  is supplied to the ink jet recording head  20  in the state where the ink tank  41  is installed in the ink jet recording head  20 . 
     FIG. 10  is a sectional view of the recording head cartridge  10 . Referring to  FIG. 10 , the recording element substrate  330  is provided on one side portion of the undersurface of the box-shaped ink jet recording head  20 . Further, the ink jet recording head  20  is, as described above, provided with the joint portion. The joint portion is formed with the ink flow path  214  extending toward the recording element substrate  330 . A flow of the ink in the thus constructed recording head cartridge  10  will be explained in a way that exemplifies the ink tank  41  for the black ink. The ink in the ink tank  41  is supplied to the interior of the ink jet recording head  20  via the ink supply port  401  of the ink tank  41  and via the joint portion. The ink supplied to the interior of the ink jet recording head  20  is further supplied to the first plate  310  of the recording element unit  300  via the ink flow path  214  within the tank holder  210  and via the ink flow path  224  within the flow path forming member  220 . Then, the ink is supplied to the ink supply port  332  of the recording element substrate  330  from the first plate  310  and further to a bubbling chamber accommodating the electro-thermal converting elements  333  and the discharge ports  337  of the recording element substrate  330 . The ink supplied to the bubbling chamber is discharged out of the discharge ports  337  toward a recording sheet defined as a recorded medium by dint of thermal energy generated by the electro-thermal converting elements  333 . 
   First Embodiment of the Present Invention 
   Next, the construction and features of the ink jet recording head according to a first embodiment of the present invention, will be described with reference to  FIGS. 1 through 4C . In the thus-constructed ink jet recording head  20  in the first embodiment of the present invention the tank holder  210  itself is molded of a resin containing a dye stuff or a pigment that absorbs the laser beams in order to dispose a non-transmissive material that does not transmit the laser beams in a junction surface area between the flow path forming member  220  for forming the ink flow path  224  and the tank holder  210 . On the other hand, the flow path forming member  220  is molded of a resin that transmits the laser beams, and only a junction surface  223  of the flow path forming member  220  is a protruded portion taking a protruded shape unlike other non-junction surfaces. Further, all the junction surfaces formed on the tank holder  210  and in the periphery of the portion formed with the liquid flow path of the flow path forming member  220 , take the same planar shape. 
   According to the first embodiment, concretely, the material used for the flow path forming member is a transparent material that transmits the laser beams and exhibits excellency in terms of the ink resistance. This material is transparent Noryl [TPN9221] of [GE Plastics] (General Electric International Inc.). Further, black Noryl [SE1X] is adopted as a material of the tank holder. A material of the flow path forming member can also involve using transparent Noryl [TN300]. 
   Note that Noryl herein connotes modified polyphenylene ether or modified polyphenylene oxide. Noryl is a resin developed by the General Electric International Inc. given above and is a material acquired by modifying polyphenylene ether (polyphenylene oxide). Noryl belongs to a category of thermoplastic resins and has a highly resistive property against acid and alkaline. Transparent Noryl described above is Noryl containing none of color materials. 
   According to the first embodiment, the ink flow path  224  is formed in the flow path forming member  220 , and a sectional configuration of the ink flow path  224  is substantially a rectangle of which one side corresponds to the tank holder  210  in the connected state. 
   The following is a description of how the ink jet recording head in the first embodiment of the present invention is constructed. In the aforementioned ink jet recording head, as shown in FIG.  FIGS. 1 ,  3 A and  4 A, after the flow path forming member  220  has been attached to the tank holder  210  in an arrow direction, the flow path forming member  220  is, as illustrated in  FIGS. 2 ,  3 B and  4 B, pressed by a press jig  53  having transmissivity of the laser beams, thereby hermetically connecting the junction surfaces together. Thereafter, a laser irradiation machine  51  irradiates the resin mold forming the tank holder  210  with the laser beams, with the result that the laser-beam-absorptive dye stuff or pigment contained in the resin mold emits the heat to melt the resin. The heat emitted at this time exothermically melts also the flow path forming member  220 , whereby the junction surface  223  in the periphery of the ink flow path  224  is connected by welding as shown in  FIG. 4C . Note that a holder receiving board  52  in  FIGS. 3A and 3B  is a board for sustaining the tank holder  210  when melting the flow path forming member to the tank holder. 
   Herein, the flow path forming member  220 , as only the junction surface thereof takes the protruded shape unlike other non-junction surfaces, improves its hermetic connectivity. Then, the melting heat of the exothermic resin of the tank holder  210  is efficiently transferred to the mold resin of the flow path forming member  220 , whereby the tank holder  210  and the flow path forming member  220  can be melted and connected to each other. A melted portion  228  is produced on the welded surface between the tank holder  210  and the flow path forming member  224 , however, a large burr as seen in the prior art does occur in the ink flow path  224 . 
   Further, all the junction surfaces formed on the tank holder  210  and in the periphery of the portion formed with the liquid flow path of the flow path forming member  220 , take the same planar shape, and hence, when a distance between a light source of the laser beams and the junction surface portion is set fixed, the periphery of the liquid flow path can be all welded, thereby enabling the manufacturing costs to be decreased. 
   According to the first embodiment, as described above, the material of the flow path forming member involves the use of transparent Noryl given above. In the case of other ink resistive resin such as a PPS (polyphenylenesulfide) material, however, this material does not well transmit the laser beams, a junction strength of the welded portion between the tank holder and the flow path forming member was insufficient, and a sufficient mechanical strength of the flow path forming member was not acquired. Moreover, the majority of other resins such as an ABS resin and polycarbonate having such a grade as to exhibit high laser beam transmissivity, which are, i.e., suited to the laser welding, were conversely inferior in terms of the ink resistance and insufficient as the materials of the flow path forming member. 
   By contrast, in the case of utilizing transparent Noryl given above as the material of the flow path forming member, the transparent Noryl well transmits the laser beams, and therefore the tank holder and the flow path forming member could be welded together at the sufficiently preferable junction strength. Besides, the sufficient mechanical strength of the flow path forming member was acquired. Further, the sufficient ink resistance was obtained. 
   Second Embodiment of the Present Invention 
   Next, a construction and features of the ink jet recording head according to a second embodiment of the present invention will be explained with reference to  FIGS. 11A ,  11 B and  11 C.  FIGS. 11A ,  11 B and  11 C are schematic side surface partial sectional views showing a step of connecting the flow path forming member to the tank holder of the ink jet recording head in the second embodiment of the present invention.  FIG. 11A  shows a relative relationship between the tank holder and the flow path forming member before the connection.  FIG. 11B  shows a state in which the flow path forming member is irradiated with the laser beam in a way that abuts the flow path forming member on the tank holder.  FIG. 11C  shows a connected state. The same members as those in the first embodiment are marked with the same reference numerals. 
   In  FIGS. 11A to 11C , the materials composing the flow path forming member  220  and the tank holder  211  are the same as those in the first embodiment. In the first embodiment, only the junction surface  223  of the flow path forming member  220  is formed as the protruded portion taking the protruded shape unlike other non-junction surfaces. According to the second embodiment, however, in both of the tank holder  211  and the flow path forming member  220 , respective junction surfaces  216  and  223  thereof are formed as protruded portions each taking the protruded shape unlike other non-junction surfaces. 
   In the second embodiment also, the ink flow path  224  is formed in the flow path forming member  220 , and a sectional configuration of the ink flow path  224  is substantially a rectangle of which one side corresponds to the tank holder  211  in the connected state. 
   The following is a description of how the ink jet recording head in the second embodiment of the present invention is constructed. In the aforementioned ink jet recording head, as shown in  FIG. 11A , after the flow path forming member  220  has been attached to the tank holder  211  in an arrow direction, the flow path forming member  220  is, as illustrated in  FIG. 11B , pressed by the press jig  53  having the transmissivity of the laser beams, thereby hermetically connecting the junction surfaces together. Thereafter, the laser irradiation machine  51  irradiates the resin mold forming the tank holder  211  with the laser beams, with the result that the laser-beam-absorptive dye stuff or pigment contained in the resin mold emits the heat to melt the resin. The heat emitted at this time exothermically melts also the flow path forming member  220 , whereby the junction surfaces  216 ,  223  in the periphery of the ink flow path  224  are connected by welding as shown in  FIG. 11G . 
   Herein, the tank holder  211  and the flow path forming member  220 , as only the junction surfaces thereof take the protruded shapes unlike other non-junction surfaces, improve their hermetic connectivity. Then, the melting heat of the exothermic resin of the tank holder  211  is efficiently transferred to the mold resin of the flow path forming member  220 , whereby the tank holder  211  and the flow path forming member  220  can be melted and connected to each other. 
   Third Embodiment of the Present Invention 
   Next, a construction and features of the ink jet recording head according to a third embodiment of the present invention will be explained with reference to  FIGS. 12A ,  12 B and  12 C.  FIGS. 12A ,  12 B and  12 C are schematic side surface partial sectional views showing a step of connecting the flow path forming member to the tank holder of the ink jet recording head in the third embodiment of the present invention.  FIG. 12A  shows a relative relationship between the tank holder and the flow path forming member before the connection.  FIG. 12B  shows a state in which the flow path forming member is irradiated with the laser beam in a way that abuts the flow path forming member on the tank holder.  FIG. 12C  shows a connected state. The same members as those in the first embodiment are marked with the same reference numerals. 
   In  FIG. 12 , the materials composing a flow path forming member  221  and a tank holder  212  are the same as those in the first embodiment. Further, as in the first embodiment, only a junction surface  223  of the flow path forming member  221  is formed as the protruded portion taking the protruded shape unlike other non-junction surfaces. 
   In the first and second embodiments, the ink flow path  224  is formed in the flow path forming member  220 , and a sectional configuration of the ink flow path  224  is substantially a rectangle of which one side corresponds to the tank holder  212  in the connected state. According to the third embodiment, the tank holder  212  and the flow path forming member  221  are formed respectively with ink flow paths  214  and  225  each taking a semi-circular shape, wherein an ink flow path  215  taking a circular shape in section in the connected state is configured and shows a symmetrical shape in section with respect to the junction surface  223  as a central surface. As shown in  FIG. 12A , after the flow path forming member  221  has been attached to the tank holder  212  in an arrow direction, the flow path forming member  221  is, as illustrated in  FIG. 12B , pressed by the press jig  53  having the transmissivity of the laser beams, thereby hermetically connecting the junction surfaces together. Thereafter, the laser irradiation machine  51  irradiates the resin mold forming the tank holder  212  with the laser beams, with the result that the laser-beam-absorptive dye stuff or pigment contained in the resin mold emits the heat to melt the resin. The heat emitted at this time exothermically melts also the flow path forming member  221 , whereby the junction surfaces in the periphery of the ink flow path  215  are connected by welding as shown in  FIG. 12C . 
   Herein, as only the junction surface of the flow path forming member  221  takes the protruded shape unlike other non-junction surfaces, the hermetic connectivity between the tank holder  212  and the flow path forming member  221  is improved. Then, the melting heat of the exothermic resin of the tank holder  212  is efficiently transferred to the mold resin of the flow path forming member  221 , whereby the tank holder  212  and the flow path forming member  221  can be melted and connected to each other. 
   Moreover, the ink flow paths formed in the tank holder  212  and the flow path forming member  221  take the semi-circular shape in section and show the symmetrical shape in section with respect to the junction surface as the central surface. Accordingly, the combined ink flow path assumes substantially the circular shape in section, whereby the ink flow path  215  with no stagnated portion can be formed. 
   Interiors of the ink flow paths of the respective tank holder unit assembled by the conventional ultrasonic wave welding and by the laser welding in the third embodiment were solidified by a resin, cut and polished, and sections of the ink flow paths were observed.  FIG. 13A  and  FIG. 13B  respectively show microscopic photos thereof. 
     FIG. 13A  shows the section of the ink flow path formed by the ultrasonic wave welding as the conventional method. 
   An example by the conventional method is that, the ultrasonic wave welding property being taken into consideration, the flow path forming member and the tank holder are formed of the same resinous material, and black Noryl [PCN2910] of [GE Plastics] (General Electric International Inc.) is adopted as a material exhibiting the excellency of the ink resistance. 
   As can be recognized from the sectional photo in  FIG. 13A , it is observed that pointed prickled burrs  1229  occur due to the ultrasonic wave vibrations when welding, and a glass filler having a diameter of 13 μm, which is added to the plastic also projects and is on the verge of falling out. 
   The reason for this is that when the flow path forming member  1220  is welded to the tank holder  1210 , the two members rub against each other due to the ultrasonic wave vibrations, and the resin melted by the friction heat and the glass filler, etc. contained in the resin are scattered over the contact portion. 
   Further, a large amount of melted burrs  1229  are generated in the ultrasonic wave welding, and hence there is a necessity of providing an extensive burr reservoir portion  1218  so that the melted burrs do not largely extend over the ink flow path  1224 , and this becomes the ink stagnated portion. The dusts occurred when in the ultrasonic wave welding are easy to stagnate and are very hard to be removed in a subsequent washing step. 
     FIG. 13B  shows a sectional photo of the tank holder unit when cut in a direction vertical to the liquid flowing direction within the ink flow path formed by utilizing the laser welding in the present example. 
   Even in the case of the laser welding, a welding burr  229  is formed slightly. As the flow path forming member  221  is just pressed against the tank holder  212 , a welding burr  229  takes a small round protruded shape protruding from the junction surface, and the ink flow path  214  is substantially circular in sectional shape. Thus, the welding burr  229  assuming the small round protruded shape does not easily fall out, and it is therefore possible to remarkably reduce the dusts generated when assembled. 
   Then, the laser-welding-based formation of the ink flow path involves a small amount of melted burrs generated, and hence it is feasible to eliminate the burr reservoir that turns out to be the ink stagnated portion, which was indispensable for the assembly based on the ultrasonic wave welding. 
   For verifying an effect that the tank holder unit formed by the laser welding has a smaller and less amount of generated dusts than by the tank holder unit formed by the conventional ultrasonic wave welding, the ink flow paths of the tank holder units assembled by the ultrasonic wave welding and by the laser welding are washed by alkaline wash water of a PH of 11.0, and the dusts contained in the wash drainage water are observed by an particle in-liquid counter made by Rion Inc.  FIG. 14  shows a conceptual diagram of the in-liquid particle measuring apparatus. 
   The number of dusts is measured (counted) such that part (25 cc/min) of the wash drainage water flowing at a rate of approximately 4.5 l/min, which has been bifurcated from a drainage hose of a wash jig, is introduced into the particle in-liquid counter, and a 1-sec dust count is detected at an interval of 3 sec on a time base for one minute since the washing was started. 
   Table 1 shows a comparison in total value between the dust counts of the dusts generated in the tank holder unit formed based on the ultrasonic wave welding shown in  FIG. 13A  and in the tank holder unit formed based on the laser welding according to the third embodiment shown in  FIG. 13B . 
   
     
       
         
             
             
             
             
           
             
               TABLE 1 
             
             
                 
             
             
                 
                 
               Ultrasonic Wave 
                 
             
             
               Particle Size of Dust 
                 
               Welding 
               Laser Welding 
             
             
                 
             
           
          
             
                 
             
          
         
         
             
             
             
             
             
          
             
               Less than 2 μm 
               846 
               pieces 
               742 
               pieces 
             
             
               Equal to or larger than 
               92 
               pieces 
               83 
               pieces 
             
             
               2 μm but less than 5 μm 
             
          
         
         
             
             
             
             
          
             
               Equal to or larger than 
               5 
               pieces 
               0 
             
             
               5 μm but less than 10 μm 
             
             
               Equal to or larger than 
               1 
               piece 
               0 
             
             
               10 μm but less than 15 μm 
             
          
         
         
             
             
             
          
             
               Equal to or larger than 
               0 
               0 
             
             
               15 μm but less than 20 μm 
             
             
               Equal to or larger than 
               0 
               0 
             
             
               20 μm but less than 25 μm 
             
             
                 
             
          
         
       
     
   
   The dust count of the dusts less than 5 μm in the laser welding is smaller by approximately 10% than in the ultrasonic wave welding. Further, none of the dusts having a particle size equal to or larger than 5 μm are recognized in the laser welding, whereas in the ultrasonic wave welding the dusts having a particle size equal to or larger than 5 μm but less than 15 μm are recognized. 
   It can be understood from this comparison that the dust generation can be made less by assembling the tank holder unit based on the laser welding than by the assembly based on the conventional ultrasonic wave welding step. 
   On the other hand, a tendency over the recent years is that an areal size of the discharge port for discharging the ink is decreased for reducing a volume of a liquid droplet discharged from the recording head as a method for performing the high-definition ink jet record. As a minimum diameter of the discharge port becomes smaller, a defective discharge caused by the discharge port which is clogged by the dusts in the ink flow path becomes easier to occur. Therefore, according to the experimental result given above, the formation of the liquid flow path based on the laser welding of the present invention can be, it is understood, preferably utilized in the case of using the recording head having the discharge port of which the minimum diameter is equal to or larger than 5 μm but less than 15 μm, especially the recording head having the discharge port of which the minimum diameter is equal to or larger than 5 μm but less than 10 μm. 
   Fourth Embodiment of the Present Invention 
   Next, a construction and features of the ink jet recording head according to a fourth embodiment of the present invention will be explained with reference to  FIGS. 15A ,  15 B and  15 C.  FIGS. 15A ,  15 B and  15 C are schematic side surface partial sectional views showing a step of connecting the flow path forming member to the tank holder of the ink jet recording head in the fourth embodiment of the present invention.  FIG. 15A  shows a relative relationship between the tank holder and the flow path forming member before the connection.  FIG. 15B  shows a state in which the flow path forming member is irradiated with the laser beam in a way that abuts the flow path forming member on the tank holder.  FIG. 15C  shows a connected state. The same members as those in the first embodiment are marked with the same reference numerals. 
   In  FIGS. 15A to 15C , the tank holder  210  as well as the flow path forming member  220  are molded of transparent Noryl of the General Electric International Inc. that is used as a material of the flow path forming member  220  in each of the embodiments discussed above. 
   Further, as in the first embodiment, only the junction surface  223  of the flow path forming member  220  is formed as the protruded portion taking the protruded shape unlike other non-junction surface. 
   According to the fourth embodiment, a laser beam absorptive coating material  226  having no transmissivity of the laser beams is coated over the junction surface  223  so that a non-transmissive material is disposed in a junction surface area with the tank holder  210  for forming the ink flow path  224 . 
   According to the fourth embodiment, as in the first and second embodiments, the ink flow path  224  is formed in the flow path forming member  220 , and a sectional configuration of the ink flow path  224  is substantially a rectangle of which one side corresponds to the tank holder  210  in the connected state. 
   After the laser beam absorptive coating material  226  composed of a coating material or a pigment that absorbs the laser beams has been, as shown in  FIG. 15A , coated over the junction surface  223  of the flow path forming member  220 , the flow path forming member  220  is attached to the tank holder  210  in an arrow direction. Thereafter, as shown in  FIG. 15B , the flow path forming member  220  is pressed by the press jig  53  having the transmissivity of the laser beams, thereby hermetically connecting the junction surfaces together. Thereafter, the laser irradiation machine  51  emits the laser beams, with the result that the laser beam absorptive coating material  226  coated over the junction surface of the flow path forming member  220  emits the heat. Then, the resins of the tank holder  210  and of the flow path forming member  220 , which are brought into contact with the laser beam absorptive coating  226 , are also exothermically melted, whereby the junction surface  223  in the periphery of the ink flow path  224  is connected by welding as shown in  FIG. 15C . 
   Herein, as only the junction surface of the flow path forming member  220  takes the protruded shape unlike other non-junction surfaces, the laser beam absorptive coating material can be coated over only the junction surface, and the exothermic laser beam absorptive coating material emits the heat only on the junction surface between the mold resin of the tank holder  210  and the mold resin of the flow path forming member  220 . These mold resins are thereby melted each other and can be connected through residuals of the laser beam absorptive coating material. 
   According to the fourth embodiment, the tank holder  210  and the flow path forming member  220  can be formed of the same resin, and it is possible to avoid an influence caused due to a difference in thermal expansion between the resins at the junction surfaces. 
   The description in the fourth embodiment is that only the junction surface of the flow path forming member  220  takes the protruded shape, however, the junction surface of the tank holder  210  or the junction surfaces of the both may also be formed in the protruded shape. In this case, the laser beam absorptive coating material may be coated over the junction surface of the tank holder  210 . 
   Fifth Embodiment of the Present Invention 
   Next, a construction and features of the ink jet recording head according to a fifth embodiment of the present invention will be explained with reference to  FIGS. 16A ,  16 B and  16 C.  FIGS. 16A ,  16 B and  16 C are schematic side surface partial sectional views showing a step of connecting the flow path forming member to the tank holder of the ink jet recording head in the fifth embodiment of the present invention.  FIG. 16A  shows a relative relationship between the tank holder and the flow path forming member before the connection.  FIG. 16B  shows a state in which the flow path forming member is irradiated with the laser beam in a way that abuts the flow path forming member on the tank holder.  FIG. 16C  shows a connected state. The same members as those in the first embodiment are marked with the same reference numerals. 
   In  FIGS. 16A to 16C , the flow path forming member  220  and the tank holder  211  are composed of the same materials as those in the first through third embodiments. Further, as in the second embodiment, only the junction surfaces of both of the tank holder  211  and the flow path forming member  220  are protruded surfaces taking the protruded shape unlike other non-junction surfaces. Moreover, according to the fifth embodiment, as in the first, second and fourth embodiments, the ink flow path  224  is formed in the flow path forming member  220 , and a sectional configuration of the ink flow path  224  is substantially a rectangle of which one side corresponds to the tank holder  211  in the connected state. In the fifth embodiment, the protruded surface serving as the junction surface of the tank holder  211  is a junction surface  217  subjected to a roughing surface treatment of making the surface rougher than other non-junction surfaces. 
   After the flow path forming member  220  has been attached to the tank holder  211  in an arrow direction as shown in  FIG. 16A , the flow path forming member  220  is pressed by the press jig  53  having the transmissivity of the laser beams as shown in  FIG. 16B , thereby hermetically connecting the junction surfaces together. Thereafter, the laser irradiation machine  51  emits the laser beams, with the result that the laser-beam-absorptive dye stuff or pigment contained in the resin mold forming the tank holder  211  emits the heat to melt the resin. The heat emitted at this time exothermically melts also the flow path forming member  220 , whereby the junction surfaces  217 ,  223  in the periphery of the ink flow path  224  are connected by welding as shown in FIG.  16 C. 
   Herein, in the tank holder  211  and the flow path forming member  220 , only the junction surfaces  217 ,  223  thereof are the protruded surfaces taking the protruded shapes unlike other non-junction surfaces, and the junction surface  217  of the tank holder  211  is subjected to the roughing surface treatment for roughing the surface. Therefore, the roughed and elevated (protruded) surface contiguous to the flow path forming member  220  is melted in a short period of time, resulting in a melted contact surface of the flow path forming member  220 . Then, the mold resins can be, with the roughed and elevated surface being centered, melted each other and firmly connected. 
   In above embodiments of the Present Invention, the flow path forming member is composed of a resin exhibiting transmissivity of laser beam. And by irradiating a periphery of the ink flow path with the laser beam from the side of the flow path forming member, the junction surface portion of the tank holder and the junction surface portion of the flow path forming member are welded. 
   It may be carried out, however, that the tank holder member is composed of a resin exhibiting transmissivity of laser beam, and the tank holder and the flow path forming member are welded by irradiating a periphery of the ink flow path with the laser beam from the side of the tank holder. 
   This application claims priority from Japanese Patent Application No. 2003-295314 filed Aug. 19, 2003, which is hereby incorporated by reference herein.