Patent Publication Number: US-10328689-B2

Title: Flow path structure, liquid ejecting head, liquid ejecting apparatus, and manufacturing method of flow path structure

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/210,059, filed Jul. 14, 2016, which claims priority to Japanese Patent Application No. 2015-146552 filed on Jul. 24, 2015, Japanese Patent Application No. 2015-146553 filed on Jul. 24, 2015 and Japanese Patent Application No. 2016-002826 filed on Jan. 8, 2016, the entireties of which are incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a technology of ejecting liquid, such as ink. 
     2. Related Art 
     A liquid ejecting head which ejects liquid, such as ink, from a plurality of nozzles is suggested in the related art. For example, in JP-A-2011-104891, a configuration in which a groove is formed on each of opposite surfaces on two substrates, and a flow path of the liquid surrounded by a wall surface of the groove is formed in the liquid ejecting head by performing laser welding with respect to the periphery of the groove and by joining the two substrates, is disclosed. In JP-A-2011-104891, considering that the welding is performed insufficiently since the heat in an end portion region of a welding part is likely to be released when laser light is radiated, and heat energy of the laser light increases in the end portion region with the thickness of the end portion region thinner than that of other parts. 
     In addition, for example, JP-A-2009-226943 discloses a configuration in which stagnation of the liquid in a reservoir that supplies the liquid to a compression chamber which generates pressure for ejecting the liquid is suppressed. In JP-A-2011-104891, considering that the stagnation is likely to be generated in a confluence region of the liquid supplied from a liquid supply port of a reservoir, the stagnation in the confluence region is controlled with a side wall of the reservoir protrude in the confluence region of the liquid, thereby improving bubble discharge performance in the reservoir. 
     However, there is a case where, in a flow path formed in a substrate by the laser welding, a flow path pipe of another flow path which communicates with the flow path is formed to protrude from a front surface of the substrate. A part which protrudes from the substrate in the flow path pipe increases to be thicker than other parts of the substrate. Therefore, when performing the welding by radiating the laser light to the substrate from the front surface on which the flow path pipe protrudes, since the protruding part of the flow path pipe is thicker than other parts of the substrate, the laser light is likely to be attenuated compared to other parts. Therefore, welding unevenness due to insufficient welding is likely to be generated. In this case, the laser light may be radiated from a flat plane side on which the flow path pipe does not protrude, but there is also a case where the laser light is not radiated from the flat plane side since a projection from the substrate increases as a structure of the flow path or a configuration of the flow path substrate has become complicated in recent years. 
     In the above-described JP-A-2011-104891, the flow path pipe which forms another flow path that communicates with the flow path formed on the substrate, protrudes from the substrate. However, the laser light is radiated from a side opposite to a side on which the flow path pipe protrudes on the substrate, and the fact that the laser light is radiated from the side on which the flow path pipe protrudes is not described at all, and is not even considered. Furthermore, as illustrated in JP-A-2011-104891, in a case where a part which protrudes from the substrate in the flow path pipe is pushed out of the region of the flow path in the substrate in a plan view, if the laser light is radiated from the side on which the flow path pipe protrudes, and the welding is performed, since the laser light is attenuated at a part at which the flow path pipe protrudes, welding unevenness due to insufficient welding is likely to be generated. When welding unevenness between each substrate is generated, there is a concern that air tightness of the flow path deteriorates. 
     In addition, since a plurality of flow paths of the liquid are provided in the liquid ejecting head, a part at which the stagnation of the liquid is generated is not limited to the confluence region of the liquid when the liquid flows into the reservoir from a supply port as described in JP-A-2009-226943. For example, there is a case where a branch flow path which branches from a main flow path of the ink is formed, and in this case, even at a branch point of the flow path, there is a concern that the stagnation of the liquid is generated. Since a part of the liquid which flows in the main flow path diverges to the branch flow path, at the branch point of the main flow path and the branch flow path, a flow of the main flow path is pulled to the branch flow path according to the flow velocity or the flow path area, and the stagnation of the liquid is likely to be generated. However, in JP-A-2009-226943, the stagnation of the liquid generated at the branch point of the flow path is not assumed. Furthermore, since the flow of the branch point between the main flow path and the branch flow path as described above is completely different from the flow of the confluence region into which the liquid flows from the supply port at a comparatively large space, such as a reservoir, as described in JP-A-2009-226943, it is not possible to employ the configuration of JP-A-2009-226943 as it is. 
     SUMMARY 
     An advantage of some aspects of the invention is to achieve at least one of reduction in welding unevenness due to laser welding and improvement of discharge performance of bubbles at a branch point of a flow path by reducing welding unevenness due to laser welding suppressing stagnation of liquid at the branch point of the flow path provided with a branched flow path. 
     Aspect 1 
     According to a preferred aspect (Aspect 1) of the invention, there is provided a flow path structure which forms a flow path of liquid, including: a light absorbing member having absorbing properties with respect to laser light; a light transmitting member which is joined to the light absorbing member and has transmitting properties with respect to the laser light; a first flow path which is surrounded by a welding interface (in other words, a welding surface) between the light absorbing member and the light transmitting member in a plan view from a direction orthogonal to the welding interface; and a second flow path which is formed in a flow path pipe which protrudes from a front surface opposite of the welding interface in the light transmitting member, and communicates with the first flow path, in which the flow path pipe is included in a region of the first flow path in the plan view. In Aspect 1, since the flow path pipe which protrudes from the front surface opposite to the welding surface in the light transmitting member is included in the region of the first flow path in a plan view from the direction orthogonal to the welding surface, it is possible to prevent the welding surface which surrounds the first flow path from overlapping the pipe surface of the flow path pipe. Therefore, it is possible to effectively reduce welding unevenness. Accordingly, it is possible to form a flow path having high air tightness. In addition, in Aspect 1, since the flow path pipe formed in the light transmitting member may be included in the region of the first flow path, it is possible to improve the degree of freedom of the sectional area of other flow path pipes, for example, the flow path pipe provided in the light absorbing member. 
     Aspect 2 
     In a preferred example (Aspect 2) of Aspect 1, the second flow path may include an enlarged diameter portion having a first tapered portion which widens in a tapered shape to a downstream side of the first flow path, toward the first flow path. In Aspect 2, since the second flow path includes the enlarged diameter portion having the first tapered portion which widens in a tapered shape to the downstream side of the first flow path, toward the first flow path, the liquid which flows toward the downstream side from the upstream side of the first flow path can be likely to flow to the second flow path from the first flow path. Therefore, it is possible to suppress the stagnation of the liquid which is likely to be generated at this part. Accordingly, since the bubbles which stay at the stagnation part of the liquid are likely to be discharged, it is possible to improve the bubble discharge performance. 
     Aspect 3 
     In a preferred example (Aspect 3) of Aspect 2, the enlarged diameter portion of the second flow path may further have a second tapered portion which widens in a tapered shape to an upstream side of the first flow path, toward the first flow path, and an inclination angle (in other words, taper angle) with respect to the second flow path of the first tapered portion may be greater than an inclination angle with respect to the second flow path of the second tapered portion. In Aspect 3, since the enlarged diameter portion of the second flow path further has the second tapered portion which widens to the upstream side in addition to the first tapered portion which widens to the downstream side of the first flow path, it is possible to enlarge the sectional area of the enlarged diameter portion of the second flow path. Therefore, it is possible to make the liquid more likely to flow to the second flow path from the first flow path. In addition, in Aspect 3, since the inclination angle with respect to the second flow path of the first tapered portion which widens to the downstream side is greater than the inclination angle with respect to the second flow path of the second tapered portion which widens in a tapered shape to the upstream side, compared to a case where the inclination angle is the same with respect to both of the first tapered portion and the second tapered portion, it is possible to prevent the sectional area of the second flow path from becoming extremely large. Therefore, it is possible to suppress deterioration of the flow velocity. In this manner, since it is possible to make the liquid more likely to flow to the second flow path from the first flow path while suppressing deterioration of the flow velocity, it is possible to further improve the discharge performance of the bubbles. 
     Aspect 4 
     In a preferred example (Aspect 4) of Aspect 2 or 3, an end portion of the enlarged diameter portion of the second flow path may be opened to an opposing surface which opposes the light absorbing member, in the light transmitting member. In Aspect 4, since the end portion of the enlarged diameter portion of the second flow path is opened to the opposing surface which opposes the light absorbing member, in the light transmitting member, it is likely to form the enlarged diameter portion in the second flow path. 
     Aspect 5 
     In a preferred example (Aspect 5) of any one of Aspects 2 to 4, a plurality of the second flow paths may be formed from an inlet flow path which communicates with the first flow path to the downstream side, the plurality of second flow paths may include a flow path disposed in the end portion on the downstream side of the first flow path, and a flow path disposed between the end portion on the downstream side of the first flow path and the inlet flow path, and, in the light absorbing member, a projection portion which protrudes toward the enlarged diameter portion of the flow path, may be formed at a position opposing the flow path disposed between the end portion on the downstream side of the first flow path and the inlet flow path in the plurality of second flow paths. In Aspect 5, since the projection portion which protrudes toward the enlarged diameter portion of the flow path, is formed at the position opposing the flow path disposed between the end portion on the downstream side of the first flow path and the inlet flow path in the plurality of second flow paths, at a branch point of the first flow path and each second flow path, a flow along the projection portion of the first flow path and the enlarged diameter portion of the second flow path is generated. Therefore, the flow toward the second flow path from the first flow path is more likely to be formed. Accordingly, since the stagnation of the liquid is suppressed at each branch point and the bubbles are likely to be discharged, it is possible to further improve the discharge performance of the bubbles at each branch point. 
     Aspect 6 
     In a preferred example (Aspect 6) of any one of Aspects 2 to 5, the first flow path may be formed from one end portion to the other end portion, the inlet flow path may be disposed between the one end portion and the other end portion, and the second flow path may be disposed at both of the one end portion and the other end portion. In Aspect 6, since the first flow path is formed from one end portion to the other end portion, the inlet flow path is disposed between one end portion and the other end portion, and the second flow path is disposed at both of one end portion and the other end portion, the liquid which flows from the inlet flow path branches and is likely to flow not only in the second flow path in one end portion but also in the second flow path in the other end portion. According to this, compared to a case where the inlet flow path is not provided between one end portion and the other end portion, since it is possible to suppress the stagnation in one end portion and the other end portion of the first flow path, the bubbles which stay in the stagnation are likely to be discharged. Accordingly, while suppressing the stagnation in one end portion and the other end portion of the first flow path, it is possible to reduce welding unevenness of laser welding. 
     Aspect 7 
     The flow path structure according to a preferred example (Aspect 7) of any one of Aspects 1to 6 may further include a third flow path which is formed in a flow path pipe that protrudes on a side opposite to the flow path pipe in which the second flow path is formed with respect to the welding surface, and communicates with the first flow path. The number of flow path pipes which forms the third flow path may be less than the number of flow path pipes which forms the second flow path, and the sectional area of the third flow path may be greater than the sectional area of the second flow path. In Aspect 7, since the sectional area of the third flow path is greater than the sectional area of the second flow path, it is possible to reduce pressure loss in the flow path. In particular, since the pressure loss is likely to be generated in a case where the plurality of second flow paths which communicate with the first flow path are present, an effect that the reduction of the pressure loss is possible, is large. Furthermore, since the third flow path is formed in a flow path pipe that protrudes on the side opposite to the flow path pipe in which the second flow path is formed with respect to the welding surface, that is, on the side opposite to the side to which the laser light is radiated, even when the sectional area of the third flow path is large, it is possible to reduce welding unevenness of the laser welding. Accordingly, while suppressing the pressure loss, it is possible to reduce welding unevenness of the laser welding. 
     Aspect 8 
     In a preferred example (Aspect 8) of Aspect 7, an outer circumference of the flow path pipe in which the third flow path is formed may have a size which exceeds a region of the first flow path in a plan view from the direction orthogonal to the welding surface. In Aspect 8, since the outer circumference of the flow path pipe in which the third flow path is formed has the size which exceeds the region of the first flow path in a plan view from the direction orthogonal to the welding surface, it is possible to further enlarge the sectional area of the third flow path. Therefore, it is possible to improve the effect of reducing the pressure loss of the first flow path. 
     Aspect 9 
     The flow path structure according to a preferred example (Aspect 9) of Aspect 7 or 8 may further include two light transmitting members which are joined to the light absorbing member and have transmitting properties with respect to the laser light. The light absorbing member may be stacked being interposed between the two light transmitting members, and the flow path pipe of the second flow path may be formed at one or both of the two light transmitting members. In Aspect 9, since two light transmitting members which are joined to the light absorbing member and have transmitting properties with respect to the laser light, are provided, it is possible to radiate the laser light from the front surfaces of both of the two light transmitting members, and to weld each of the two light transmitting members to the light absorbing member. In this case, since the flow path pipe of the second flow path included in the region of the first flow path is formed at one or both of the two light transmitting members, even when the laser light is radiated from the front surface of any light transmitting member, it is possible to reduce welding unevenness. 
     Aspect 10 
     In a preferred example (Aspect 10) of Aspect 9, the flow path pipe of the second flow path may be formed at one of the two light transmitting members, and the flow path pipe of the third flow path may be formed at the other one of the two light transmitting members. In Aspect 10, since the flow path pipe of the second flow path is formed at one of the two light transmitting members, and the third flow path is formed at the other one, it is possible to further enlarge the sectional area of the third flow path. Therefore, it is possible to reduce the pressure loss of the first flow path. In addition, by joining a second substrate on which the flow path pipe of the second flow path included in the region of the first flow path is formed, to a first substrate, by the laser welding, it is possible to reduce welding unevenness. 
     Aspect 11 
     In a preferred example (Aspect 11) of Aspect 9 or 10, a filter interposed between the two light transmitting members may be provided in the light absorbing member. In Aspect 11, since the filter interposed between the two light transmitting members is provided in the light absorbing member, compared to a case where the filter is provided in any of the two light transmitting members, it is not necessary to dispose the filter not to overlap in the radiation direction of the laser light. Therefore, it is possible to improve the degree of freedom of design, such as the disposition or the size of the filter. 
     Aspect 12 
     According to aspect preferred aspect (Aspect 12) of the invention, there is provided a liquid ejecting head including: the flow path structure according to any one of Aspects 1 to 11; and nozzles which eject liquid from the flow path structure by driving a driving element. In Aspect 12, since the flow path structure according to any one of Aspects 1 to 11 is provided, welding unevenness due to the laser welding is reduced. Therefore, it is possible to provide the liquid ejecting head in which a flow path having high air tightness is formed. 
     Aspect 13 
     According to aspect preferred aspect (Aspect 13) of the invention, there is provided a liquid ejecting apparatus including: a transporting mechanism which transports a medium; and the liquid ejecting head according to the aspect which ejects liquid to the medium. In Aspect 12, since the liquid ejecting head according to Aspect 12 is provided, welding unevenness due to the laser welding is reduced. Therefore, it is possible to provide the liquid ejecting apparatus in which a flow path having high air tightness is formed. A preferable example of the liquid ejecting apparatus is a printing apparatus which ejects ink to the medium, such as a printing paper sheet, but the use of the liquid ejecting apparatus according to the invention is not limited to printing. 
     Aspect 14 
     According to a preferred aspect (Aspect 14) of the invention, there is provided a manufacturing method of a flow path structure, the method including: forming a flow path groove of a first flow path on one or both of opposing surfaces of a light absorbing member having absorbing properties with respect to laser light and a light transmitting member having transmitting properties with respect to the laser light; forming a flow path pipe which protrudes from a front surface opposite to the opposing surface which opposes the light absorbing member, in the light transmitting member and forming a second flow path which communicates with the first flow path in the flow path pipe; stacking the light absorbing member and the light transmitting member so that the opposing surfaces thereof are in contact with each other; and forming the first flow path by radiating the laser light toward the light transmitting member and by forming a welding surface that surrounds the flow path groove without overlapping the flow path pipe in the radiation direction. In Aspect 14, in the radiation direction (including the direction orthogonal or diagonal to the welding surface) of the laser light, the welding surface which surrounds the first flow path does not overlap a pipe surface of the flow path pipe. Therefore, it is possible to effectively reduce welding unevenness. Accordingly, it is possible to form a flow path having high air tightness. 
     Aspect 15 
     In a preferred example (Aspect 15) of Aspect 14, the second flow path may include an enlarged diameter portion having a first tapered portion which widens in a tapered shape to a downstream side of the first flow path, toward the first flow path. In Aspect 15, since the second flow path includes the enlarged diameter portion having the first tapered portion which widens in a tapered shape to the downstream side of the first flow path, toward the first flow path, the liquid which flows to the downstream side from the upstream side of the first flow path can be likely to flow to the second flow path from the first flow path. Therefore, it is possible to suppress the stagnation of the liquid generated at the part. Accordingly, since the bubbles which stay at the stagnation part of the liquid are likely to be discharged, it is possible to improve the bubble discharge performance. 
     Aspect 16 
     In a preferred example (Aspect 16) of Aspect 15, the enlarged diameter portion of the second flow path may further have a second tapered portion which widens in a tapered shape to an upstream side of the first flow path, toward the first flow path, and an inclination angle with respect to the second flow path of the first tapered portion may be greater than an inclination angle with respect to the second flow path of the second tapered portion. In Aspect 16, since the enlarged diameter portion of the second flow path further has the second tapered portion which widens to the upstream side in addition to the first tapered portion which widens to the downstream side of the first flow path, it is possible to enlarge the sectional area of the enlarged diameter portion of the second flow path. Therefore, it is possible to make the liquid more likely to flow to the second flow path from the first flow path. In addition, in Aspect 16, since the inclination angle with respect to the second flow path of the first tapered portion which widens to the downstream side is greater than the inclination angle with respect to the second flow path of the second tapered portion which widens in a tapered shape to the upstream side, compared to a case where the inclination angle is the same with respect to both the first tapered portion and the second tapered portion, it is possible to prevent the sectional area of the second flow path from becoming extremely large. Therefore, it is possible to suppress deterioration of the flow velocity. In this manner, since it is possible to make the liquid more likely to flow to the second flow path from the first flow path while suppressing deterioration of the flow velocity, it is possible to further improve the discharge performance of the bubbles. 
     Aspect 17 
     In a preferred example (Aspect 17) of Aspect 15 or 16, an end portion of the enlarged diameter portion of the second flow path may be opened to an opposing surface which opposes the light absorbing member, in the light transmitting member. In Aspect 17, since the end portion of the enlarged diameter portion of the second flow path is opened to the opposing surface which opposes the light absorbing member, in the light transmitting member, it is likely to form the enlarged diameter portion in the second flow path. 
     Aspect 18 
     In a preferred example (Aspect 18) of any one of Aspects 15 to 17, a plurality of the second flow paths may be formed from an inlet flow path which communicates with the first flow path to the downstream side, the plurality of second flow paths may include a flow path disposed in the end portion on the downstream side of the first flow path, and a flow path disposed between the end portion on the downstream side of the first flow path and the inlet flow path, and, in the light absorbing member, a projection portion which protrudes toward the enlarged diameter portion of the flow path, may be formed at a position opposing the flow path disposed between the end portion on the downstream side of the first flow path and the inlet flow path in the plurality of second flow paths. In Aspect 18, since the projection portion which protrudes toward the enlarged diameter portion of the flow path, is formed at a position opposing the flow path disposed between the end portion on the downstream side of the first flow path and the inlet flow path in the plurality of second flow paths, at the branch point of the first flow path and the second flow path, a flow along the projection portion of the first flow path and the enlarged diameter portion of the second flow path, is generated. Therefore, the flow from the first flow path to the second flow path is more likely to be formed. Accordingly, since the stagnation of the liquid is suppressed at each branch point and the bubbles are likely to be discharged, it is possible to further improve the discharge performance of the bubbles at each branch point. 
     Aspect 19 
     In a preferred example (Aspect 19) of any one of Aspects 15 to 18, the first flow path may be formed from one end portion to the other end portion, the inlet flow path may be disposed between the one end portion and the other end portion, and the second flow path may be disposed at both of the one end portion and the other end portion. In Aspect 19, the first flow path is formed from one end portion to the other end portion, the inlet flow path is disposed between one end portion and the other end portion, and the second flow path is disposed at both of one end portion and the other end portion, the liquid which flows from the inlet flow path branches, and is likely to flow not only in the second flow path of one end portion but also in the second flow path of the other end portion. According to this, compared to a case where the inlet flow path is not provided between one end portion and the other end portion, since it is possible to suppress the stagnation in one end portion and the other end portion of the first flow path, the bubbles which stay in the stagnation are likely to be discharged. Accordingly, while suppressing the stagnation in one end portion and the other end portion of the first flow path, it is possible to reduce welding unevenness of the laser welding. 
     Aspect 20 
     In a preferred example (Aspect 20) of any one of Aspects 14 o 19, a third flow path which is formed in a flow path pipe that protrudes on a side opposite to the flow path pipe in which the second flow path is formed with respect to the welding surface, and communicates with the first flow path, may further be provided, the number of flow path pipes which forms the third flow path is formed may be less than the number of flow path pipes which forms the second flow path, and the sectional area of the third flow path may be greater than the sectional area of the second flow path. In Aspect 20, since the sectional area of the third flow path is greater than the sectional area of the second flow path, it is possible to reduce the pressure loss in the flow path. In particular, since the pressure loss is likely to be generated in a case where the plurality of second flow paths which communicate with the first flow path are present, an effect that the reduction of the pressure loss is possible is large. Furthermore, since the third flow path is formed in the flow path pipe which protrudes on a side opposite to the flow path pipe in which the second flow path is formed with respect to the welding surface, that is, on a side opposite to the side to which the laser light is radiated, even when the sectional area of the third flow path is enlarged, it is possible to reduce welding unevenness of the laser welding. Accordingly, while reducing the pressure loss, it is possible to reduce welding unevenness of the laser welding. 
     Aspect 21 
     In a preferred example (Aspect 21) of Aspect 20, an outer circumference of the flow path pipe in which the third flow path is formed may have a size which exceeds a region of the first flow path in a plan view from a direction orthogonal to the welding surface. In Aspect 21, since the outer circumference of the flow path pipe in which the third flow path is formed has the size which exceeds the region of the first flow path in a plan view from the direction orthogonal to the welding surface, it is possible to further enlarge the sectional area of the third flow path. Therefore, it is possible to improve the effect of reducing the pressure loss of the first flow path. 
     Aspect 22 
     In a preferred example (Aspect 22) of Aspect 20 or 21, two light transmitting members which are joined to the light absorbing member and have transmitting properties with respect to the laser light, may further be provided, the light absorbing member may be stacked being interposed between the two light transmitting members, and the flow path pipe of the second flow path may be formed at one or both of the two light transmitting members. In Aspect 22, since two light transmitting members which are joined to the light absorbing member and have transmitting properties with respect to the laser light, are further provided, by radiating the laser light from the front surface of both of the two light transmitting members, it is possible to weld each of the two light transmitting members to the light absorbing member. In this case, since the flow path pipe of the second flow path included in the region of the first flow path is formed at one or both of the two light transmitting members, even when the laser light is radiated from the front surface of any light transmitting member, it is possible to reduce welding unevenness. 
     Aspect 23 
     In a preferred example (Aspect 23) of Aspect 22, the flow path pipe of the second flow path may be formed at one of the two light transmitting members, and the flow path pipe of the third flow path may be formed at the other one of the two light transmitting members. In Aspect 23, since the flow path pipe of the second flow path is formed at one of the two light transmitting members, and the flow path pipe of the third flow path is formed at the other one, it is possible to further enlarge the sectional area of the third flow path. Therefore, it is possible to reduce the pressure loss of the first flow path. In addition, by joining the second substrate on which the flow path pipe of the second flow path included in the region of the first flow path is formed, to a first substrate, by the laser welding, it is possible to reduce welding unevenness. 
     Aspect 24 
     In a preferred example (Aspect 24) of Aspect 22 or 23, a filter interposed between the two light transmitting members may be provided in the light absorbing member. In Aspect 24, since the filter interposed between the two light transmitting members is provided in the light absorbing member, compared to a case where the filter is provided in any of the two light transmitting members, it is not necessary to dispose the filter not to overlap in the radiation direction of the laser light. Therefore, it is possible to improve the degree of freedom of the design, such as the disposition or the size of the filter. 
     Aspect 25 
     In a preferred example (Aspect 25) of any one of Aspects 14 to 24, an angle of the radiation direction of the laser light with respect to the welding surface is constant. In this case, since the angle of the radiation direction of the laser light with respect to the welding surface is constant, compared to a case where the radiation angle of the laser light changes, it is easy to perform the laser welding. 
     Aspect 26 
     According to a preferred aspect (Aspect 26), there is provided a flow path structure which forms a flow path of liquid, including: a first substrate; a second substrate joined to the first substrate; and a first flow path which is surrounded by a fixing surface on which the first substrate and the second substrate are fixed, in which a second flow path which branches from the first flow path and in which the liquid flows in the direction intersecting with the fixing surface, is formed in one of the first substrate and the second substrate, and a projection portion which protrudes toward the second flow path at a branch point of the first flow path and the second flow path is formed in the other one of the first substrate and the second substrate, the projection portion includes a wall surface on the upstream side and a wall surface on the downstream side in the first flow path, and the wall surface on the upstream side of the projection portion has an inclined surface which is inclined so that the height of the projection portion increases toward the downstream side with respect to the direction of the flow in the first flow path. 
     In Aspect 26, since the second flow path which branches from the first flow path is provided, the projection portion which protrudes toward the second flow path is formed at the branch point of the first flow path and the second flow path, and the inclined surface which is inclined so that the height of the projection portion increases toward the downstream side with respect to the direction of the flow in the first flow path, is provided on the wall surface on the upstream side of the projection portion, at the branch point of the first flow path and the second flow path, a part of the liquid which flows in the first flow path forms a flow which is guided to the second flow path being oriented to the inclined surface having the wall surface on the upstream side of the projection portion. According to this, the stagnation of the liquid is suppressed at the branch point of the first flow path and the second flow path, and the bubbles are likely to be discharged from the second flow path. Accordingly, it is possible to improve the bubble discharge performance at each branch point. 
     Aspect 27 
     In a preferred example (Aspect 27) of Aspect 26, the wall surface on the downstream side of the projection portion may have the inclined surface which is inclined so that the height of the projection portion decreases toward the downstream side with respect to the direction of the flow in the first flow path, and the inclination angle of the wall surface on the upstream side of the projection portion with respect to the direction of the flow in the first flow path may be greater than the inclination angle of the wall surface on the downstream side of the projection portion with respect to the direction of the flow in the first flow path. 
     In Aspect 27, since the inclination angle of the wall surface on the upstream side of the projection portion with respect to the direction of the flow in the first flow path is greater than the inclination angle of the wall surface on the downstream side, the liquid which flows in the first flow path can be likely to flow to the second flow path. Accordingly, since it is possible to enhance the suppression effect of the stagnation of the branch point, and the bubbles are more likely to be discharged from the second flow path, it is possible to further improve the discharge performance of the bubbles at each branch point. In addition, in Aspect 27, since the inclination angle of the wall surface on the downstream side of the projection portion with respect to the direction of the flow in the first flow path is smaller than the inclination angle of the wall surface on the upstream side, the flow of the liquid which flows further on the downstream side than the projection portion in the first flow path becomes smooth. Therefore, it is possible to reduce the stagnation of the liquid which flows further on the downstream side than the projection portion. 
     Aspect 28 
     In a preferred example (Aspect 28) of Aspect 26 or 27, in the sectional area of the first flow path on the section orthogonal to the direction of the flow in the first flow path, the sectional area of the first flow path further on the downstream side than the projection portion, may be smaller than the sectional area of the first flow path further on the upstream side than the projection portion. In a case where the sectional area of the first flow path is constant, the flow velocity of the liquid which flows in the first flow path is reduced when passing through the projection portion or the branch point, and the bubble discharge performance deteriorates. 
     At this point, in Aspect 28, since the sectional area of the first flow path further on the downstream side than the projection portion is smaller than the sectional area of the first flow path further on the upstream side than the projection portion, it is possible to suppress deterioration of the flow velocity of the liquid which flows in the first flow path further on the downstream side than the projection portion. Accordingly, it is possible to improve the discharge performance of the bubbles further on the downstream side than the projection portion. 
     Aspect 29 
     In a preferred example (Aspect 29) of Aspect 28, the first substrate may be the light absorbing member having absorbing properties with respect to the laser light, the second substrate may be the light transmitting member having transmitting properties with respect to the laser light, the fixing surface which surrounds the first flow path may be the welding surface which is welded by the laser light, the second flow path may be formed in the flow path pipe which protrudes from the front surface opposite to the welding surface in the second substrate and is included in the region of the first flow path in a plan view from the direction orthogonal to the welding surface, and the height of the first flow path further on the downstream side than the projection portion may be lower than the height of the first flow path further on the upstream side than the projection portion, among the heights of the first flow path on the section orthogonal to the direction of the flow in the first flow path. 
     In Aspect 29, since the height of the first flow path further on the downstream side than the projection portion is lower than the height of the first flow path further on the upstream side than the projection portion, among the heights of the first flow path on the section orthogonal to the direction of the flow in the first flow path, the sectional area of the first flow path further on the downstream side than the projection portion becomes smaller than the sectional area of the first flow path further on the upstream side than the projection portion. Accordingly, since it is possible to suppress deterioration of the flow velocity of the liquid which flows in the first flow path further on the downstream side than the projection portion, it is possible to improve the discharge performance of the bubbles further on the downstream side than the projection portion. 
     In addition, in Aspect 29, since the second flow path is formed in the flow path pipe which protrudes from the front surface opposite to the welding surface in the second substrate and is included in the region of the first flow path in a plan view from the direction orthogonal to the welding surface, it is possible to make the welding surface which surrounds the first flow path not to overlap the pipe surface of the flow path pipe. Therefore, it is possible to effectively reduce welding unevenness of the welding surface welded by the laser light. Accordingly, it is possible to form a flow path having high air tightness. Furthermore, in Aspect 29, since the sectional area of the first flow path is adjusted by the height of the first flow path, compared to a case where the sectional area of the first flow path is adjusted by the width of the first flow path, the region of the first flow path surrounded by the welding surface does not narrow. Therefore, it is significantly effective that it is not necessary to adjust the size of the flow path pipe in accordance with the width of the first flow path so that the welding surface which surrounds the first flow path does not overlap the pipe surface of the flow path pipe. 
     Aspect 30 
     In a preferred example (Aspect 30) of any one of Aspects 26 to 29, the second flow path may include the enlarged diameter portion having a tapered portion which widens in a tapered shape to the downstream side of the first flow path, toward the branch point of the first flow path, and when the projection portion and the enlarged diameter portion of second flow path are viewed in a plan view on the section along the direction of the flow in the first flow path, a virtual line which extends from the wall surface on the upstream side of the projection portion along the inclined surface may pass through the region in which the tapered portion of the enlarged diameter portion is formed. 
     In Aspect 30, since the enlarged diameter portion having a tapered portion which widens in a tapered shape to the downstream side of the first flow path, is provided toward the branch point of the first flow path, and when the projection portion and the enlarged diameter portion of second flow path are viewed in a plan view on the section along the direction of the flow in the first flow path, a virtual line which extends from the wall surface on the upstream side of the projection portion along the inclined surface passes through the region in which the tapered portion of the enlarged diameter portion is formed, it is possible to guide a part of the flow of the liquid of the first flow path to the tapered portion of the enlarged diameter portion formed in the second flow path along the inclination surface on which the wall surface on the upstream side of the projection portion extends. Accordingly, since it is possible to make the flow of the liquid of the first flow path likely to flow to the second flow path, it is possible to improve the effect of improving the discharge performance of the bubbles. 
     Aspect 31 
     In a preferred example (Aspect 31) of any one of Aspects 26 to 30, the plurality of second flow paths which branch from the first flow path may be provided, and in a case where there are N (1≤N) branch points on the downstream side of a first branch point toward the downstream side from the upstream side of the first flow path, among a plurality of branch points of the first flow path and the second flow path, when the height of the first flow path on the section orthogonal to the direction of the flow in the first flow path is hp, and when a ratio of the height of the projection portion with respect to the height hp of the first flow path is X, the ratio X of the height of the projection portion of an M-th (1≤M≤N) branch point from the upstream side of the first flow path, is within a range of 1−(N−M+2)/(N+1)&lt;X&lt;1−((N-M+1)/(N+1)). It is possible to adjust the sectional area of the first flow path at each branch point by the height of the projection portion. In this case, since it is possible to suppress deterioration of the flow velocity as the height of the projection portion increases, to that extent, it is possible to improve the discharge performance of the bubbles. However, when the height of the projection portion becomes extremely high, the area of the wall surface of the projection portion with which the flow of the liquid in the first flow path comes into contact increases. Therefore, the pressure loss increases, and rather, the flow velocity deteriorates. At this point, in Aspect 31, it is possible to calculate a preferable range of the height of the projection portion at each branch point in order to achieve both the effect of improving the discharge performance of the bubbles and the effect of suppressing the increase in the pressure loss. In other words, in Aspect 31, since the ratio X of the height of the projection portion of the M-th (1≤M≤N) branch point from the upstream side of the first flow path is within the range of 1−(N−M+2)/(N+1)&lt;X&lt;1−((N-M+1)/(N+1)), it is possible to achieve both the effect of improving the discharge performance of the bubbles and the effect of suppressing the increase in the pressure loss. 
     Aspect 32 
     In a preferred example (Aspect 32) of any one of Aspects 26 to 31, the first substrate may be the light absorbing member having absorbing properties with respect to the laser light, the second substrate may be the light transmitting member having the transmitting properties with respect to the laser light, the fixing surface which surrounds the first flow path may be the welding surface which is welded by the laser light, the first flow path may be formed in one of first substrate and the second substrate. In Aspect 32, since the first flow path surrounded by the welding surface welded by the laser light is formed in one of the first substrate and the second substrate, compared to a case where the flow path groove of the first flow path is welded to be provided in both of the first substrate and the second substrate, when the first substrate and the second substrate are stacked to oppose each other, even when any of the first substrate and the second substrate is generated, it is possible to form the predetermined first flow path. 
     Aspect 33 
     According to a preferred aspect (Aspect 33) of the invention, there is provided a liquid ejecting head including: the flow path structure according to any one of Aspects 26 to 32; and nozzles which eject the liquid from the flow path structure by driving of a driving element. A preferable example of the liquid ejecting head is a printing apparatus which ejects the ink, but the use of the liquid ejecting apparatus according to the invention is not limited to printing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a configuration view of a printing apparatus which employs a liquid ejecting apparatus according to a first embodiment of the invention. 
         FIG. 2  is an exploded perspective view of a liquid ejecting head of the first embodiment. 
         FIG. 3  is an exploded perspective view in a case where the liquid ejecting head of the first embodiment is viewed from another angle. 
         FIG. 4  is a plan view when the liquid ejecting head of the first embodiment is viewed from a printing medium side. 
         FIG. 5  is an exploded perspective view of a liquid ejecting unit illustrated in  FIG. 2 . 
         FIG. 6  is a sectional view of an ejecting head portion illustrated in  FIG. 5 . 
         FIG. 7  is a side view and a plan view of a flow path structure illustrated in  FIG. 2 . 
         FIG. 8  is a sectional perspective view illustrating a flow path structure in a first comparative example. 
         FIG. 9  is a view illustrating the flow path structure in the first embodiment, and is a sectional perspective view of the flow path structure illustrated in  FIG. 7  taken along line IX-IX. 
         FIG. 10  is a partial sectional view of the flow path structure taken along line X-X illustrated in  FIG. 7 . 
         FIG. 11  is a side view and a plan view of a part of the flow path structure illustrated in  FIG. 10 . 
         FIG. 12  is a process view illustrating a manufacturing method of the flow path structure in the first embodiment. 
         FIG. 13  is a partial sectional view of the flow path structure according to a modification example of the first embodiment. 
         FIG. 14  is a partial sectional view of the flow path structure according to another modification example of the first embodiment. 
         FIG. 15  is a partial sectional view illustrating a configuration of the flow path structure according to a second embodiment of the invention. 
         FIG. 16  is a side view and a plan view of a substrate which configures a part of the flow path structure illustrated in  FIG. 15 . 
         FIG. 17  is a sectional perspective view of a part of the flow path structure illustrated in  FIG. 15  taken along the line XVII-XVII. 
         FIG. 18  is a view illustrating an action of a part of the flow path structure in a second comparative example. 
         FIG. 19  is a view illustrating an action of a part of the flow path structure in the second embodiment. 
         FIG. 20  is a partial sectional view of the flow path structure according to a modification example of the second embodiment. 
         FIG. 21  is a partial sectional view of the flow path structure according to another modification example of the second embodiment. 
         FIG. 22  is a partial sectional view of the flow path structure according to another modification example of the second embodiment. 
         FIG. 23  is a sectional view illustrating a relationship between a sectional shape of the flow path and the height of the projection portion illustrated in  FIG. 22 . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Liquid Ejecting Apparatus 
     First, a liquid ejecting apparatus according to an embodiment of the invention will be described by using an ink jet type printing apparatus as an example.  FIG. 1  is a partial configuration view of a printing apparatus  100  according to the embodiment of the invention. The printing apparatus  100  is a liquid ejecting apparatus which ejects ink which is an example of liquid to a printing medium (ejecting target) M, such as a printing paper sheet, and includes a control device  10 , a transporting mechanism  12 , a liquid ejecting head  14 , and a pump  16 . A liquid container (ink cartridge)  18  which stores a plurality colors of ink I is mounted in the printing apparatus  100 . In the first embodiment, the ink I of four colors, such as cyan (C), magenta (M), yellow (Y), and black (B) is stored in the liquid container  18 . 
     The control device  10  integrally controls each element of the printing apparatus  100 . The transporting mechanism  12  transports the printing medium M in the Y direction based on the control by the control device  10 . However, a structure of the transporting mechanism  12  is not limited to the above-described example. The pump  16  is an air supply device which supplies air A (A 1 , A 2 ) of two systems to the liquid ejecting head  14  based on the control by the control device  10 . The air A 1  and the air A 2  are gas used in controlling the flow path on the inside of the liquid ejecting head  14 . The pump  16  can independently pressurize each of the air A 1  and the air A 2  to each other. The liquid ejecting head  14  ejects the ink I supplied from the liquid container  18  to the printing medium M based on the control by the control device  10 . The liquid ejecting head  14  of the first embodiment is a line head which is long in the X direction intersecting with the Y direction. In addition, hereinafter, the direction perpendicular to the X-Y plane (plane parallel to a front surface of the printing medium M) will be described as the Z direction. The ejecting direction of the ink I by the liquid ejecting head  14  corresponds to the Z direction. 
     Liquid Ejecting Head 
       FIGS. 2 and 3  are exploded perspective views illustrating a configuration of the liquid ejecting head  14  illustrated in  FIG. 1 . As illustrated in  FIGS. 2 and 3 , the liquid ejecting head  14  is configured to include a flow path structure G 1 , a liquid path control portion G 2 , and a liquid ejecting portion G 3 . The flow path structure G 1 , the liquid path control portion G 2 , and the liquid ejecting portion G 3  are accumulated in the Z direction in this order. The liquid ejecting portion G 3  is a structure which accommodates and supports six liquid ejecting units U 3  in a housing  142 . 
       FIG. 4  is a plan view on an opposing surface which opposes the printing medium M in the liquid ejecting portion G 3 . As illustrated in  FIG. 4 , six liquid ejecting units U 3  are arranged along the X direction. Each liquid ejecting unit U 3  is provided with a plurality (six in the example illustrated in the first embodiment) of ejecting head portions  70  arranged along the X direction. Each ejecting head portion  70  includes a head chip which ejects the ink I from a plurality of nozzles N. The plurality of nozzles N of one ejecting head portion  70  are arranged in two rows along the W direction which is inclined by a predetermined angle with respect to the X direction and the Y direction. The ink I of four systems (four colors) are supplied in parallel to each ejecting head portion  70  of the liquid ejecting unit  3 . The plurality of nozzles N of one ejecting head portion  70  are divided in four sets, and the inks I different in each set are ejected. 
     The air A (A 1 , A 2 ) of two systems are supplied from the pump  16  to the flow path structure G 1  together with the supply of the ink I of four systems from the liquid container  18 . The flow path structure G 1  distributes each of the ink I of four systems and each air A of two systems, to six systems which correspond to liquid ejecting units U 3  different from each other. In other words, the distribution number (six) of the ink I of one system by the flow path structure G 1  exceeds the number K (K=4) of the types of the ink I. 
     The liquid path control portion G 2  is an element which controls the flow path (for example, opening and closing of the flow path or the pressure in the flow path) of the liquid ejecting head  14 , and is configured to include six flow path control units U 2  which correspond to liquid ejecting units U 3  different from each other. The ink I of four systems and the air A of two systems are supplied to six flow path control units U 2  in parallel as being distributed by the flow path structure G 1 . Each flow path control unit U 2  controls the opening and closing or the pressure of the flow path of the ink I of four systems distributed to each liquid ejecting unit U 3  by the flow path structure G 1 , in accordance with the air A of two systems. 
     After the distribution by the flow path structure G 1 , the ink I of four systems which pass through each flow path control unit U 2  is supplied to six liquid ejecting units U 3  in parallel. As illustrated in  FIG. 5  which will be described later, each liquid ejecting unit U 3  is provided with a liquid distributing portion  60 . The liquid distributing portion  60  distributes each ink I of four systems supplied from the flow path control unit U 2  of the previous stage, to six systems which corresponds to ejecting head portions  70  different from each other. In other words, the ink I of four systems after the distribution is supplied to each of six ejecting head portions  70  in parallel by the liquid distributing portion  60 . Each ejecting head portion  70  ejects ink I of each of four systems from the nozzles N different from each other. 
     As illustrated in  FIG. 2 , four supply ports SI 3  are formed on an opposing surface which opposes the liquid path control portion G 2  in each liquid ejecting unit U 3  of the liquid ejecting portion G 3 . In a state where the liquid path control portion G 2  and the liquid ejecting portion G 3  (housing  142 ) are fixed to each other, each flow path pipe DI 2  which forms an outlet flow path of the flow path control unit U 2 , is inserted into each supply port SI 3  of each liquid ejecting unit U 3 . Therefore, the ink I of each system is supplied to four supply ports SI 3  of each liquid ejecting unit U 3 , in parallel from the flow path pipe DI 2  of the flow path control unit U 2 . 
       FIG. 5  is an exploded perspective view of one arbitrary liquid ejecting unit U 3 . As illustrated in  FIG. 5 , the liquid ejecting unit U 3  is configured to join six ejecting head portions  70  fixed to a fixing plate  58 , to an accumulating body of a filter portion  52 , a communicating member  54 , a basic wiring substrate  56 , and the liquid distributing portion  60 . The filter portion  52  is an element which removes the bubbles or foreign substances contained in each ink I supplied from the liquid path control portion G 2 . As illustrated in  FIG. 5 , in the filter portion  52 , four supply ports SI 3  to which each ink I is supplied via the liquid path control portion G 2  are formed, and four filters  526  which correspond to the ink I supplied from each supply port SI 3  are provided. The communicating member  54  makes an outflow port of four filter portions  52  communicate with the liquid distributing portion  60 . The communicating member  54  is a flat plate material formed of an elastic material (for example, rubber), and forms four through-holes  542  which communicate with each outflow port of four filter portions  52 . The liquid distributing portion  60  distributes each ink I of four systems supplied from each supply port  60 A via each through-hole  542  of the communicating member  54 , to six systems which correspond to each ejecting head portion  70 . 
     A separate wiring base plate  78  is joined to each of ejecting head portions  70 . The separate wiring base plate  78  is inserted into an insertion port (slit)  60 C formed in the liquid distributing portion  60 , and is joined to the basic wiring substrate  56 . Each wiring base plate  78  is a flexible wiring substrate (chip on film (COF)) for electrically connecting the basic wiring substrate  56  and each ejecting head portion  70 . The fixing plate  58  is a member having a shape of a flat plate which supports each ejecting head portion  70 , and is formed of, for example, a metal having high rigidity, such as stainless steel. As illustrated in  FIG. 5 , six opening portions  582  which correspond to the ejecting head portions  70  different from each other, are formed in the fixing plate  58 . Each opening portion  582  is a rectangular through-hole which is long in the W direction in a plan view. 
       FIG. 6  is a sectional view (section perpendicular to the W direction) of one ejecting head portion  70 . As illustrated in  FIG. 6 , the ejecting head portion  70  accumulates a pressure chamber forming substrate  72  and an oscillation plate  73  on one front surface of a flow path forming substrate  71 , and includes a head chip in which a nozzle plate  74  and the compliance substrate  75  are installed on the other front surface. The plurality of nozzles N are formed on the nozzle plate  74 . In addition, as illustrated in  FIG. 6 , since a structure which corresponds to each row of the nozzles N is formed substantially symmetrically in one ejecting head portion  70 , hereinafter, a structure of the ejecting head portion  70  will be described considering one row of nozzles N for convenience. 
     The flow path forming substrate  71  is a flat plate material which configures the flow path of the ink I. In the flow path forming substrate  71 , an opening portion  712 , a supply flow path  714 , and a communicating flow path  716 , are formed. The supply flow path  714  and the communicating flow path  716  are formed in each nozzle N, and the opening portion  712  continuously connected across the plurality of nozzles N which eject the ink I of one system. The pressure chamber forming substrate  72  is a flat plate material in which the plurality of opening portions  722  which correspond to the nozzles N different from each other are formed. The flow path forming substrate  71  or the pressure chamber forming substrate  72  is formed, for example, on a silicon single crystalline substrate. 
     The compliance substrate  75  is a mechanism which suppresses (absorbs) pressure variation in the flow path of the ejecting head portion  70 , and is configured to include a sealing plate  752  and a supporting body  754 . The sealing plate  752  is a film-like flexible member, and the supporting body  754  fixes the sealing plate  752  to the flow path forming substrate  71  so that the opening portion  712  and each supply flow path  714  of the flow path forming substrate  71  are blocked. 
     The oscillation plate  73  is installed on the front surface opposite to the flow path forming substrate  71  in the pressure chamber forming substrate  72 . The oscillation plate  73  is a member having a shape of a flat plate which can elastically oscillate, and is configured of an accumulating layer of an elastic film formed of an elastic material, such as a silicon oxide, and an insulation film formed of an insulation material, such as zirconium oxide. As illustrated in  FIG. 6 , the oscillation plate  73  and the flow path forming substrate  71  oppose each other at an interval on the inner side of each opening portion  722  formed on the pressure chamber forming substrate  72 . A space nipped by the flow path forming substrate  71  and the oscillation plate  73  on the inner side of each opening portion  722 , functions as a pressure chamber (cavity) C which applies pressure to the ink. The pressure chambers C which communicate with each nozzle N are respectively arranged along the W direction. 
     On the front surface opposite to the pressure chamber forming substrate  72  in the oscillation plate  73 , piezoelectric elements  732  which function as driving elements corresponding to each nozzle N, are respectively formed. Each piezoelectric element  732  is an accumulating body which interposes a piezoelectric body between electrodes that opposes each other. As the piezoelectric element  732  oscillates together with the oscillation plate  73  by the supply of a driving signal, the pressure in the pressure chamber C varies, and the ink I in the pressure chamber C is ejected from the nozzle N. Each piezoelectric element  732  is sealed and protected by a protecting plate  76  fixed to the oscillation plate  73 . 
     A supporting body  77  is fixed to the flow path forming substrate  71  and the protecting plate  76 . The supporting body  77  is integrally formed, for example, by molding a resin material. In the supporting body  77 , a recessed portion  772  which configures a liquid storage portion (reservoir) R is formed together with the opening portion  712  of the flow path forming substrate  71 . An opening of the recessed portion  772  is blocked by a circumferential edge of the opening portion  712  of the flow path forming substrate  71  in a state of communicating with the opening portion  712  of the flow path forming substrate  71 . In the recessed portion  772 , an opening portion  774  which is opened to a side surface of the supporting body  77  is formed, and the opening portion  774  is blocked by a lid portion  775 . 
     The liquid storage portion R is configured of a space made of the recessed portion  772  of the supporting body  77 , the opening portion  774 , and an opening portion  322  of a flow path forming portion  32 . In this manner, in the opening portion  774 , it is possible to increase a volume of the liquid storage portion R by forming the opening portion  774 , compared to a case where the opening portion  774  is not formed. In addition, the opening portion  774  of the supporting body  77  may not be formed. The above-described sealing plate  752  of the compliance substrate  75  configures the wall surface (bottom surface) of the liquid storage portion R, and absorbs the pressure variation of the ink in the liquid storage portion R. 
     As illustrated in  FIG. 5 , in each ejecting head portion  70 , a supply port  771  which supplies the ink I of each system from the outflow port of the liquid distributing portion  60  is formed, and the supply port  771  communicates with the liquid storage portion R. Accordingly, the ink I of each system after the distribution by the liquid distributing portion  60  is supplied and stored in the liquid storage portion R via the supply port  771  of the ejecting head portion  70  from the outflow port of the liquid distributing portion  60 . The ink I stored in the liquid storage portion R is distributed and fills each pressure chamber C by the plurality of supply flow paths  714 , and is ejected to the outside (printing medium M side) passing through the communicating flow path  716  and the nozzle N from each pressure chamber C. 
     An end portion of the separate wiring base plate  78  is joined to the oscillation plate  73  illustrated in  FIG. 6 . The separate wiring base plate  78  is a flexible substrate (flexible wiring substrate) in which the wiring for transferring the driving signal or the power voltage to each piezoelectric element  732  is formed. The separate wiring base plate  78  protrudes via a slit  762  formed in the protecting plate  76  and a slit  776  formed in the supporting body  77 , and is connected to the basic wiring substrate  56  as described above. The driving signal or the power voltage is supplied to the piezoelectric element  732  of each ejecting head portion  70  via each separate wiring base plate  78  from the basic wiring substrate  56 . 
     Configuration of Flow Path Structure in First Embodiment 
     Here, a configuration of the flow path structure G 1  in which the flow path of the fluid (liquid or gas) in the first embodiment will be described in more detail.  FIG. 7  is a side view and a plan view of the flow path structure G 1 . As illustrated in  FIG. 7 , the flow path structure G 1  is a structure having a shape of a flat plate in which a first substrate  27  and a second substrate  28  are joined to each other in a state of opposing each other. The first substrate  27  and the second substrate  28  are a flat plate material which is long in the X direction, and for example, are formed of a resin material, such as polypropylene. The first substrate  27  and the second substrate  28  are joined by the laser welding as will be described later. 
     The first substrate  27  is provided with a first surface  271  opposite to the second substrate  28 , and a first opposing surface  272  which opposes the second substrate  28  and is opposite to the first surface  271 . Similarly, the second substrate  28  is provided with a second surface  281  opposite to the first substrate  27 , and a second opposing surface  282  which opposes the first substrate  27  and is opposite to the second surface  281 . 
     In  FIG. 7 , a plan view of the first surface  271  and a plan view of the second surface  281  are described together. On the first surface  271  of the first substrate  27 , four flow path pipes SI 1  which become an inlet flow path which supplies the ink I (C, M, Y, K) of each system from the liquid container  18 , and two flow path pipes SA 1  which become the inlet flow path which supplies the gas, here, the air A (A 1 , A 2 ), of two systems from the pump  16 , are formed. Each of the flow path pipes SI 1  and SA 1  which become the inlet flow paths protrudes to a negative side in the Y direction from the first surface  271  of the first substrate  27 . 
     On the second surface  281  of the second substrate  28 , six flow path pipes DI 1  which become outlet flow paths corresponding to the ink I of each system, and a flow path pipe DA 1  which becomes two outlet flow paths corresponding to the air A of each system, are separately formed in each of six liquid ejecting units U 3 . Six flow path pipes DI 1  which correspond to the ink I of one arbitrary system are arranged in the X direction at a substantially equivalent interval, and six flow path pipes DA 1  which correspond to the air A of one arbitrary system are arranged in the X direction at a substantially equivalent interval. Each of the flow path pipes DI 1  and DA 1  which become the outlet flow paths protrude to a positive side in the Y direction from the second surface  281  of the second substrate  28 . 
     As illustrated by a dotted line in  FIG. 7 , between the first opposing surface  272  of the first substrate  27  and the second opposing surface  282  of the second substrate  28 , four flow paths PI 1  of the liquid which correspond to the ink I of each system, and two flow paths PA 1  of the gas which correspond to the air A of each system, are formed. Each flow path PI 1  and each flow path PA 1  are present in a shape of a substantially straight line along the X direction across substantially the entire region of the range in which six flow path control units U 2  are arranged in a plan view. On both sides which nip two flow paths PA 1  which correspond to the air A in a plan view, four flow paths PI 1  which correspond to the ink I are positioned. In addition, each flow path PA 1  which corresponds to the air A is bent in a plan view to detour an attaching hole  23 . 
     Each flow path PI 1  is formed to overlap one flow path pipe SI 1  for supplying the ink I in a plan view, and communicates with an inlet flow path H 1  formed in the flow path pipe SI 1  to penetrate the first substrate  27 . Similarly, each flow path PA 1  is formed to overlap one flow path pipe SA 1  for supplying the air A, and communicates with the inlet flow path H 1  formed in the flow path pipe SA 1  to penetrate the first substrate  27 . 
     In this manner, each flow path PI 1  is a flow path which communicates with the inlet flow path H 1  formed in one flow path pipe SI 1 , and outlet flow paths H 2  formed in each of six flow path pipes DI 1 . Each flow path PA 1  is a flow path which communicates with the inlet flow path H 1  formed in one flow path pipe SA 1 , and the outlet flow paths H 2  formed in each of six flow path pipes DA 1 . The flow paths PI 1  and PA 1  accumulate the first substrate  27  and the second substrate  28  so that the first opposing surface  272  and the second opposing surface  282  come into contact with each other, and are configured by fixing the periphery of the flow path groove formed in one or both thereof. In other words, here, the flow paths PI 1  and PA 1  are a region surrounded by the fixing surface. The fixing surface which surrounds the flow paths PI 1  and PA 1  may be, for example, a welding surface by the laser welding, or an adhering surface by an adhesive, but here, a case where the fixing surface is the welding surface by the laser welding, will be described as an example. 
     In a case where the flow paths PI 1  and PA 1  are formed by performing the laser welding with respect to the first substrate  27  and the second substrate  28 , one of the first substrate  27  and the second substrate  28  is configured of a light transmitting member having transmitting properties with respect to the laser light, and the other one of the first substrate  27  and the second substrate  28  is configured of a light absorbing member having absorbing properties with respect to the laser light. In addition, the laser light is radiated from the front surface of the substrate configured of the light transmitting member, and the welding is performed. In the first embodiment, a case where the first substrate  27  is configured of the light absorbing member, the second substrate  28  is configured of the light transmitting member, the laser light is radiated from the second surface  281  of the second substrate  28 , and the welding is performed, is described as an example. 
     Meanwhile, in the flow path structure G 1  of the first embodiment, on the second surface  281  of the second substrate  28  which radiates the laser light, six flow path pipes DI 1  are formed to protrude from the second surface  281 . Therefore, the thickness of a part of the pipe surface of the flow path pipe DI 1  increases to be thicker than that of other parts only by the length (thickness) of protrusion of the flow path pipe DI 1  from the second surface  281 . In this configuration, if the welding surface overlaps the pipe surface of the flow path pipe DI 1  in the radiation direction of the laser light, since the laser light is likely to be attenuated at a part which overlaps the pipe surface of the flow path pipe DI 1 , compared to other parts, there is a problem that welding unevenness due to insufficient welding is likely to be generated. When welding unevenness is generated, there is a concern that the air tightness of the flow path deteriorates. 
     Here, in the embodiment, as illustrated in  FIG. 7 , in the region of each of the flow paths PI 1  and PA 1  in a plan view, the pipe surface (outer circumference) of the flow path pipes DI 1  and DA 1  are included. According to this, in the radiation direction of the laser light, since it is possible to make the welding surface which surrounds each of the flow paths PI 1  and PA 1  not to overlap the pipe surface of the flow path pipes DI 1  and DA 1 , it is possible to effectively reduce welding unevenness. 
     Here, a flow path structure of the flow path structure G 1  of the first embodiment will be described in more detail comparing to a first comparative example.  FIG. 8  is a sectional perspective view illustrating a flow path structure of the first comparative example, and illustrates a case where a welding surface W′ which surrounds a first flow path P′ in the radiation direction of laser light L′ overlaps the pipe surface of a flow path pipe D′ of a second flow path Q′.  FIG. 9  is a view illustrating the flow path structure in the first embodiment, and is a sectional perspective view of a flow path structure G illustrated in  FIG. 7  taken along line IX-IX.  FIG. 9  illustrates a case where a welding surface W which surrounds a first flow path P in the radiation direction of laser light L does not overlap the pipe surface of a flow path pipe D of a second flow path Q which corresponds to the flow path pipes DI 1  and DA 1  of the outlet flow path H 2 .  FIGS. 8 and 9  are views cut by a plane including the welding surfaces W and W′ after the laser welding. In addition, the “first flow path” in the first embodiment is a flow path which is surrounded by the welding surface by the laser welding, and in which the fluid (liquid or gas) flows. At this point, the flow path PI 1  of each liquid and the flow path PA 1  of each gas correspond to the “first flow path” of the first embodiment, and the outlet flow path H 2  corresponds to the “second flow path”. Meanwhile, in the second embodiment which will be described later, a flow path configuration having improved discharge performance of the bubbles included in the liquid which flows in the flow path, is described as an example. Therefore, each flow path PI 1  of the liquid corresponds to the “first flow path” in the second embodiment. 
     In  FIG. 8 , the flow path pipe D′ which forms the second flow path Q′ is formed to protrude from a second surface  281 ′ of a second substrate  28 ′, on the positive side in the Z direction, and the periphery of a flow path groove  273 ′ formed on a first substrate  27 ′ is welded by the laser light L′, and accordingly, the first flow path P′ surrounded by the welding surface W′ is formed. In  FIG. 9 , the flow path pipe D which forms the second flow path Q is formed to protrude from the second surface  281  of the second substrate  28  on the positive side in the Z direction, the periphery of a flow path groove  273  formed on the first substrate  27  is welded by the laser light L, and accordingly, the first flow path P surrounded by the welding surface W is formed. 
     In a configuration of the first example of  FIG. 8 , in a plan view from the radiation direction of the laser light L′, that is, the direction (negative side in the Z direction) orthogonal to the welding surface W′, the pipe surface of the flow path pipe D′ is disposed exceeding the region of the first flow path P′. In the configuration of the first comparative example, the welding surface W′ which surrounds the first flow path P′ in the radiation direction of the laser light L′ overlaps the pipe surface of the flow path pipe D′ of the second flow path Q′. The thickness of a part of the pipe surface of the flow path pipe D′ increases to be thicker than that of the thickness of the second surface  281 ′ only by the length (thickness) of protrusion of the flow path pipe D from the second surface  281 ′. Therefore, as illustrated in  FIG. 8 , in the radiation direction of the laser light, when a welding surface W″ which overlaps the pipe surface of the flow path pipe DI 1  on the welding surface W′ is present, since laser light La′ radiated to the welding surface W″ is likely to be attenuated compared to the laser light L of other parts, welding unevenness due to the insufficient welding is likely to be generated. 
     Meanwhile, in the configuration of the first embodiment illustrated in  FIG. 9 , in a plan view from the radiation direction of the laser light L, that is, the direction (negative side in the Z direction) orthogonal to the welding surface W, the pipe surface of the flow path pipe D is disposed in the region of the first flow path P. Accordingly, it is possible to make the welding surface W which surrounds the first flow path P in the radiation direction of the laser light L not to overlap the pipe surface of the flow path pipe D of the second flow path Q. Therefore, since the attenuation of the laser light L due to the difference in the thickness is not generated, it is possible to sufficiently perform the welding, and to effectively reduce welding unevenness. Accordingly, it is possible to form the first flow path P having high air tightness. 
     The flow path structure of the first embodiment will be specifically described in more detail by using the flow path PI 1  of the liquid as an example. The flow path PI 1  of the liquid in the first embodiment has four systems, and flow path structures of a part of the liquid path structure G 1  including each flow path PI 1  are configured to be similar to each other. Here, a flow path structure of a part including the flow path PI 1  of one arbitrary system will be taken and described.  FIG. 10  is a partial sectional view of the flow path structure G 1  taken along line X-X illustrated in  FIG. 7 .  FIG. 11  is a side view and a plan view in a case where the first substrate  27  and the second substrate  28  which configure a part of the flow path structure G 1  illustrated in  FIG. 10  are exploded. 
     As illustrated in  FIGS. 10 and 11 , in the first opposing surface  272  of the first substrate  27 , the flow path groove  273  which extends in the X direction along the first opposing surface  272 , and the inlet flow path H 1  which communicates with the flow path groove  273 , are formed. The flow path groove  273  is a groove having a substantially rectangular section which configures the flow path PI 1  that corresponds to the first flow path, and the inlet flow path H 1  is a through-hole which is formed in the flow path pipe SI 1  that protrudes from the first surface  271  of the first substrate  27 . The flow path groove  273  is formed across two end portions  273   a  and  273   b  which are separated from each other in the X direction of the flow path PI 1 , and the inlet flow path H 1  is disposed between the end portions  273   a  and  273   b.    
     On the second opposing surface  282  of the second substrate  28 , six outlet flow paths H 2  which correspond to the second flow path are formed in the direction (Z direction) perpendicular to the second opposing surface  282 . The outlet flow path H 2  is a through-hole which is formed in the flow path pipe DI 1  that protrudes from the second surface  281  of the second substrate  28 . Six outlet flow paths H 2  are disposed across both sides of the inlet flow path H 1  in a plan view from the Z direction. The inlet flow path H 1  is disposed to be closer to one end portion  273   a  than the center between one end portion  273   a  and the other end portion  273   b . Therefore, the number of outlet flow paths H 2  disposed between the inlet flow path H 1  and each of the end portions  273   a  and  273   b , varies. 
     Specifically, the outlet flow paths H 2  are respectively disposed one by one in both of the end portions  273   a  and  273   b  of the flow path groove  273 . In the middle (more right side than the inlet flow path H 1  in  FIGS. 10 and 11 ) of the inlet flow path H 1  and one end portion  273   a , one outlet flow path H 2  is disposed, and in the middle (more left side than the inlet flow path H 1  of  FIGS. 10 and 11 ) of the inlet flow path H 1  and the other end portion  273   b , three outlet flow paths H 2  are disposed. 
     According to the flow path structure, the ink which flows from the inlet flow path H 1  branches to the negative side and the positive side in the X direction, and flows toward both of the end portions  273   a  and  273   b  of the flow path PI 1 . In other words, in the flow path PI 1 , a flow of the ink toward one end portion  273   a  further on the downstream side from the inlet flow path H 1  on the upstream side, and a flow of the ink toward the other end portion  273   a  on the downstream side from the inlet flow path H 1  on the upstream side in the orientation reverse thereto, are generated. 
     The ink which flows toward one end portion  273   a  of the flow path PI 1  branches and flows out to each of the outlet flow path H 2  of the end portion  273   a  and one outlet flow path H 2  between the end portion  273   a  and the inlet flow path H 1 . The ink which flows toward the other end portion  273   b  of the flow path PI 1  branches and flows out to each of the outlet flow path H 2  of the end portion  273   b  and three outlet flow paths H 2  between the end portion  273   b  and the inlet flow path H 1 . In addition, the number and the disposition of the inlet flow path H 1  and the outlet flow path H 2  are not limited to the description above. 
     The first substrate  27  and the second substrate  28  configured in this manner, are accumulated so that each of the first opposing surface  272  and the second opposing surface  282  come into contact with each other, and the periphery of the flow path groove  273  is welded by the laser light radiated toward the second surface  281  of the second substrate  28 . Accordingly, the flow path (first flow path) PI 1  is configured of a space which is configured of the inner wall surface of the flow path groove  273  of the first substrate  27  and the wall surface opposing the flow path groove  273  of the second substrate  28 . 
     The welding surface W formed in this manner has, for example, a shape of an annular belt illustrated by halftone dot meshing in a plan view of the first substrate  27  and the second substrate  28  in  FIG. 9 . The flow path PI 1  is a region (region on the inner side of an inner circumferential edge of the welding surface W having a shape of an annular belt) surrounded by the welding surface W. As illustrated in a plan view of the second substrate  28  of  FIG. 11 , all of six flow path pipes DI 1  including the pipe surfaces thereof are disposed to be included in the region of the flow path PI 1 . Accordingly, it is possible to make the welding surface W which surrounds the flow path PI 1  in the radiation direction of the laser light not to overlap the pipe surface of the flow path pipe DI 1 . Therefore, since the attenuation of the laser light L due to the difference in the thickness is not generated as described above, it is possible to effectively reduce welding unevenness. In addition, a case where the flow path pipe DI 1  of  FIGS. 10 and 11  protrudes in the direction orthogonal to the welding surface W is illustrated as an example, but the flow path pipe DI 1  may protrude in the direction diagonal to the welding surface W. 
     Regarding the “flow path surrounded by the welding surface” here, when considering a case where there is an error in flatness of each of the first substrate  27  configured of the light absorbing member and the second substrate  28  configured of the light transmitting member, even when the entire melted surface of the light absorbing member does not abut against the light transmitting member, both are fixed as surfaces, and as a result, the flow path PI 1  may be formed. Therefore, in a case where a void of both of the surfaces is sealed, an interval between an opposing surface of the light absorbing member and an opposing surface of the light transmitting member is equal to or less than 0.3 mm, and a case where the light absorbing member of the part is melted is also included in the “welding surface”. 
     In addition, whether or not the void between the light absorbing member and the light transmitting member is sealed (air tightness) is measured, for example, by the following method. The air of +50 kPa is sent by blocking the entire other flow path which communicates with the flow pat of the measurement target, and a pressure change of the flow path of the measurement target is measured. In this case, when the pressure change in 5 seconds after the air is sent is equal to or less than 1 kPa, the flow path of the measurement target is sealed. 
     In addition, according to the flow path structure illustrated in  FIG. 10 , since the inlet flow path H 1  of the flow path PI 1  is between the outlet flow paths H 2  (second flow paths) of both of the end portions  273   a  and  273   b  of the flow path PI 1 , the ink which flows from the inlet flow path H 1  branches, and is likely to flow not only to the outlet flow path H 2  of one end portion  273   a  but also the outlet flow path H 2  of the other end portion  273   b . According to this, compared to a case where the inlet flow path H 1  is not present between both of the end portions  273   a  and  273   b , since it is possible to suppress the stagnation of the ink in both of the end portions  273   a  and  273   b  of the flow path PI 1 , the bubbles which stay in the stagnation of the ink are likely to be discharged. Accordingly, while suppressing the stagnation in both of the end portions  273   a  and  273   b  of the flow path PI 1 , it is possible to reduce welding unevenness of the laser welding. 
     Manufacturing Method of Flow Path Structure 
     Next, a manufacturing method of the flow path structure G 1  will be described.  FIG. 12  is a process view illustrating the manufacturing method of the flow path structure G 1 . Here, the manufacturing method of the flow path structure G 1  will be described by using a partial sectional view of the flow path structure G 1  taken along line X-X illustrated in  FIG. 7 . First, in a process a of  FIG. 12 , the first substrate  27  is manufactured by a thermoplastic resin which absorbs the laser light. As the thermoplastic resin having light absorbing properties, a material which is made by mixing a predetermined coloring agent, such as carbon black, dye, or pigment, into polyamide (PA) or the like, can be employed. 
     In the first surface  271  of the first substrate  27 , the flow path pipe SI 1  which protrudes from the first surface  271  is formed, and a through-hole which configures the inlet flow path (third flow path) H 1  is formed in the flow path pipe SI 1 . On the first opposing surface  272  of the first substrate  27 , the flow path groove  273  which configures the flow path (first flow path) PI 1  is formed. In this case, in the first surface  271  of the first substrate  27 , the flow path pipes SI 1  and SA 1  of another system and the inlet flow path H 1  are also formed, and in the first opposing surface  272  of the first substrate  27 , the flow path groove  273  which configures the flow paths PI 1  and PA 1  of another system is also formed. The first substrate  27  may be manufactured by an integrated mold, or may be manufactured by processing a flat plate material. 
     Next, in a process b of  FIG. 12 , the second substrate  28  is manufactured by the thermoplastic resin which penetrates the laser light. Examples of the thermoplastic resin having the light transmitting properties include polyamide (PA), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), styrene acrylonitrile copolymer, an ABS resin, an acrylic resin (PMMA), polycarbonate (PC), and polybutylene terephthalate (PBT). In addition, as necessary, a material which is made by adding reinforcing fiber, such as glass fiber or carbon fiber, or a coloring material, as necessary, may be used. On the second surface  281  of the second substrate  28 , six flow path pipes DI 1  which protrude from the second surface  281  are formed, and the outlet flow path (second flow path) H 2  through-hole which passes through the inside of each flow path pipe DI 1  and penetrates from the second surface  281  to the second opposing surface  282 , is formed. At this time, on the second substrate  28 , the flow path pipes DI 1  and DA 1  of another system and the outlet flow path H 2  through-hole are also formed. The second substrate  28  may be manufactured by an integrated mold, or may be manufactured by processing a flat plate material. 
     Next, in a process c of  FIG. 12 , the first substrate  27  and the second substrate  28  are accumulated so that each of the first opposing surface  272  and the second opposing surface  282  comes into contact with each other, and in a process d of  FIG. 12 , the laser light L is radiated from the second surface  281  side of the second substrate  28 . Then, the laser light L penetrates the second substrate  28  made of the light transmitting member, and is absorbed by the first substrate  27  made of the light absorbing member. At this time, the dye or pigment included in the light absorbing member generates the heat, the resin is melted, and at this time, the generated heat is transferred to the light absorbing member. The light transmitting member is melted by the transferred heat, and the welding surface W is formed. In addition, the welding due to the laser light L may be performed only with respect to a part to be the welding surface W, or may be integrally performed with respect to a part to be the welding surface W and a part to be the flow path. 
     In addition, the type of the laser light L is used being appropriately selected according to the absorption spectrum or the plate thickness (transmission length) of the material of the second substrate  28  which makes the laser light transmit. Specifically, for example, the laser light, such as glass:neodymium 3+  laser, YAG:neodymium 3+  laser, ruby laser, helium neon laser, Krypton laser, argon laser, H 2  laser, N 2  laser, or semiconductor laser, can be employed. 
     By the laser light L, the flow path (first flow path) PI 1  surrounded by the welding surface W is formed by welding the periphery of the flow path groove  273 . At this time, the flow path PI 1  and the flow path PA 1  of another system are also similarly formed. In this manner, the flow path structure G 1  having the flow path structure illustrated in  FIGS. 10 and 11  are formed. As described above, in the flow path structure G 1  of the first embodiment, the pipe surface (outer circumference) of the flow path pipe DI 1  is included in the region of each flow path PI 1 , and the pipe surface (outer circumference) of the flow path pipe DA 1  is included in the region of each flow path PA 1 . Therefore, the welding surface W which surrounds each flow path PI 1  does not overlap the pipe surface of the flow path pipe DI 1  in the radiation direction when the laser light L is radiated, the welding surface W which surrounds each flow path PA 1  does not overlap the pipe surface of the flow path pipe DA 1 , and thus, it is possible to effectively reduce welding unevenness of each welding surface W. Accordingly, it is possible to improve the air tightness of the flow path pipe DI 1  formed to be surrounded by the welding surface W. 
     In addition, the radiation direction of the laser light L may be inclined with respect to the welding surface W, but by making the direction orthogonal to the welding surface W as illustrated in a process d of  FIG. 12 , it is possible to make the laser light L penetrate the light transmitting member having the same thickness across the entire welding surface W without considering the influence of attenuation or refraction. In addition, it is preferable that the angle of the laser light L in the radiation direction with respect to the welding surface W is constant across the entire welding surface W. According to this, compared to a case where the radiation angle of the laser light L changes, the laser welding is likely to be performed. In addition, the above-described light absorbing member and the light transmitting member are not limited to the member which absorbs (or transmits) the laser light L 100%. A light absorbing ratio (or light transmitting ratio) with respect to a wavelength of at least one laser light L beam of the light absorbing member and the light transmitting member may be different, and the light transmitting member may be more likely to transmit the laser light L than the light absorbing member. Therefore, the light absorbing ratio (or light transmitting ratio) of the light absorbing member and the light transmitting light may less than 100%. 
     In addition, in the flow path structure illustrated in  FIG. 10 , the flow path pipe SI 1  of the inlet flow path H 1  functions as the inlet flow path H 1  of the flow path PI 1 , but it is possible to consider the flow path pipe SI 1  as a flow path pipe of the third flow path which protrudes on a side opposite to the flow path pipe DI 1  of the outlet flow path H 2  which serves as the second flow path with respect to the welding surface W of the flow path PI 1  which serves as the first flow path. The third flow path is formed to protrude on a side opposite to the flow path pipe in which the second flow path is formed with respect to the welding surface W, that is, on a side opposite to the side which radiates the laser light. Therefore, as the flow path exceeds the region of the first flow path formed to be surrounded by the welding surface W, without enlarging the sectional area of the flow path pipe of the third flow path, it is possible to reduce welding unevenness without influencing the laser welding. 
     Therefore, in the first embodiment, in a plan view from the positive side in the Z direction as illustrated in  FIG. 11 , the outer circumference of the flow path pipe SI 1  is enlarged to the extent of exceeding the region of the flow path PI 1  which serves as the first flow path formed to be surrounded by the welding surface W, and the sectional area of the inlet flow path H 1  of the flow path pipe SI 1  is enlarged to be greater than the sectional area of the flow path pipe DI 1  of the outlet flow path H 2 . By enlarging the outer circumference of the flow path pipe SI 1 , it is possible to further enlarge the sectional area of the inlet flow path H 1 . In this manner, by enlarging the sectional area of the inlet flow path H 1 , it is possible to reduce the pressure loss in the flow path PI 1 . In particular, since the pressure loss is likely to be generated in a case where the plurality of outlet flow paths H 2  which communicate with the flow path PI 1  are present as illustrated in  FIG. 10 , an effect that the reduction of the pressure loss is possible, is large. Accordingly, while reducing the pressure loss, it is possible to reduce welding unevenness of the laser welding. 
     In addition, as the flow path pipe formed on the first surface  271  of the first substrate  27 , another flow path pipe which configures the third flow path that communicates with the flow path PI 1 , may further be provided. The third flow path in this case may be the inlet flow path of the flow path PI 1 , and may be the outlet flow path of the flow path PI 1 . Since the sectional area of the third flow path can be enlarged to be greater than that of the second flow path as described above, in a case where the plurality of third flow paths are provided, when the number of third flow paths increases with respect to the number of second flow paths, it is possible to influence the flow of the second flow path. Therefore, it is preferable that the number of third flow paths is smaller than the number of second flow paths. 
     In addition, in the flow path structure illustrated in  FIG. 10 , a case where the flow path groove  273  of the flow path PI 1  is formed on the first substrate  27  side, is described as an example, but the invention is not limited thereto. For example, as illustrated in  FIG. 13 , a flow path groove  283   a  may be formed on the second opposing surface  282  on the second substrate  28  side. The flow path structure illustrated in  FIG. 13  is formed by accumulating the first substrate  27  and the second substrate  28 , and by joining the periphery of the flow path groove  283   a  by the laser welding. Accordingly, the flow path PI 1  is formed by the space formed on the inner wall of the flow path groove  283   a  of the second substrate  28 , and on the wall surface of the first substrate  27  which opposes the flow path groove  283   a . Even in this case, as illustrated in  FIG. 13 , in a plan view, as the pipe surface of the flow path pipe DI 1  is included in the region of the flow path PI 1 , it is possible to make the welding surface W which surrounds the flow path PI 1  not to overlap the pipe surface of the flow path pipe DI 1 . Therefore, it is possible to effectively reduce welding unevenness due to the laser welding. 
     In addition, in the first embodiment, a sectional shape when the flow path PI 1  is viewed in a sectional view on the section orthogonal to the flow direction of the flow path PI 1 , forms a curved surface on which the flow path width narrows when approaching the first surface  271 , on the first surface  271  side of the first substrate  27 , as illustrated in  FIG. 9 . The sectional shape of the flow path PI 1  is not limited thereto, and may be rectangular, but forming the curved surface as illustrated in  FIG. 9  makes the stagnation of the angle portion of the flow path PI 1  more unlikely to be generated. In addition, as illustrated in  FIG. 13 , on the contrary to  FIG. 9 , the flow path section of the flow path PI 1  may form a curved surface on which the flow path width narrows when approaching the second surface  281 , on the second surface  281  side of the second substrate  28 . 
     In addition, the first embodiment employs the flow path structure G 1  having two-layered structure in which two substrates (the first substrate  27  and the second substrate  28 ) are joined as illustrated in  FIG. 10 , as an example, but the invention is not limited thereto, and the flow path structure G 1  having three-layered structure in which three substrates are joined, may be employed. For example, the flow path structure G 1  having three-layered structure illustrated in  FIG. 14  is joined to the first substrate  27  made of one light absorbing member, and is provided with second substrates  28   a  and  28   b  made of two light transmitting members having transmitting properties with respect to the laser light. The first substrate  27  is accumulated to be nipped between two second substrates  28   a  and  28   b.    
     The first substrate  27  is provided with an opposing surface  272   a  which opposes the second substrate  28   a , and an opposing surface  272   b  which is a surface opposite to the opposing surface  272   a  and opposes the second substrate  28   b . The second substrate  28   a  is provided with an opposing surface  282   a  which opposes the first substrate  27 , and a second surface  281   a  opposite to the opposing surface  282   a . The second substrate  28   b  is provided with an opposing surface  282   b  which opposes the first substrate  27 , and a first surface  281   b  opposite to the opposing surface  282   b.    
     The flow path PI 1  is divided into a first flow path chamber PI 1   a  and a second flow path chamber PI 1   b , by a filter F provided in the first substrate  27 . The first flow path chamber PI 1   a  is a space surrounded by an inner wall of a first flow path hole  273   c  formed on the opposing surface  272   a  of the first substrate  27 , and a wall surface of the second substrate  28   a  which opposes the first flow path hole  273   c . The second flow path chamber PI 1   b  is a space surrounded by an inner wall of a second flow path hole  273   d  formed on the opposing surface  272   b  of the first substrate  27 , and an inner wall of a flow path groove  283   b  formed on the opposing surface  282   b  of the second substrate  28   b.    
     The flow path pipe SI 1  of one inlet flow path H 1  is formed to protrude from the first surface  281   b  of the second substrate  28   b , and the flow path pipes DI 1  of six outlet flow paths H 2  are formed to protrude from the second surface  281   a  of the second substrate  28   a . Each of the outlet flow paths H 2  communicate with the first flow path chamber PI 1   a  of the flow path PI 1 . The inlet flow path H 1  communicates with the second flow path chamber PI 1   b  of the flow path PI 1 . According to the flow path structure, the ink which flows from the inlet flow path H 1  flows in the second flow path chamber PI 1   b  of the flow path PI 1  via the filter F from the first flow path chamber PI 1   a  of the flow path PI 1 , and flows out of each outlet flow path H 2 . The filter F captures the bubbles or the foreign substances from the ink supplied to the inlet flow path H 1 . The ink from which the bubbles or the foreign substances are removed by the passage of the filter F, flows out of each outlet flow path H 2 . 
     The first flow path chamber PI 1   a  of the flow path PI 1  is formed to be surrounded by a welding surface Wa by the laser welding between the opposing surface  282   a  of the second substrate  28   a  and the opposing surface  272   a  of the first substrate  27 . The second flow path chamber PI 1   b  of the flow path PI 1  is formed to be surrounded by a welding surface Wb by the laser welding between the opposing surface  282   b  of the second substrate  28   b  and the opposing surface  272   b  of the first substrate  27 . 
     In this manner, since the first substrate  27  made of the light absorbing member is accumulated to be nipped between two second substrates  28   a  and  28   b  made of the light transmitting members in the flow path structure G 1  illustrated in  FIG. 14 , the flow path PI 1  can be formed by the laser welding from both sides of the second substrates  28   a  and  28   b . Specifically, in a state where the first substrate  27  is accumulated to be nipped between two second substrates  28   a  and  28   b , laser light La is radiated from the second surface  281   a  of the second substrate  28   a , and laser light Lb is radiated from the first surface  281   b  of the second substrate  28   b . Accordingly, the first flow path chamber PI 1   a  of the flow path PI 1  is formed by the welding surface Wa welded by the laser light La, and the second flow path chamber PI 1   b  of the flow path PI 1  is formed by the welding surface Wb welded by the laser light Lb. 
     In the flow path structure G 1  illustrated in  FIG. 14 , since the flow path PI 1  is formed by the laser welding from both sides of the second substrates  28   a  and  28   b , all of the end surfaces (outer circumferences) of each of the flow path pipe DI 1  and the flow path pipe SI 1  are included in the region of the flow path PI 1  in a plan view from the Z direction, not only with respect to the flow path pipe DI 1  which forms the outlet flow path H 2  but also with respect to the flow path pipe SI 1  which forms the inlet flow path H 1 . At this point, in the configuration illustrated in  FIG. 14 , not only the flow path pipe DI 1  but also the flow path pipe SI 1  corresponds to the flow path pipe which forms the second flow path. Therefore, it is possible to make the end surface of each of the flow path pipe DI 1  and the flow path pipe SI 1  not to overlap the welding surfaces Wa and Wb in the radiation direction of both of the laser light La and laser light Lb. Accordingly, it is possible to reduce welding unevenness of the welding surfaces Wa and Wb. 
     However, the invention is not limited thereto. The first substrate  27  may be joined to one of the second substrates  28   a  and  28   b  by the laser welding, and the first substrate  27  may be joined to the other one of the second substrates  28   a  and  28   b  by an adhesive or the like. According to this, it is possible to provide a flow path pipe in which the third flow path that exceeds the region of the flow path PI 1  which is the first flow path is formed, on one of the second substrates  28   a  and  28   b  to which the laser welding is not performed. For example, similar to the flow path pipe SI 1  illustrated in  FIG. 11 , the flow path pipe SI 1  illustrated in  FIG. 14  may be enlarged to the extent of exceeding the region of the flow path PI 1 , and the sectional area of the inlet flow path H 1  of the flow path pipe SI 1  may be enlarged to be greater than the sectional area of the flow path pipe DI 1  of the outlet flow path H 2 . Accordingly, it is possible to reduce the pressure loss in the flow path PI 1 . The flow path pipe SI 1  corresponds to the flow path pipe in which the third flow path is formed. In this case, as the second substrate  28   a  on which the flow path pipe DI 1  of the outlet flow path H 2  is formed and the first substrate  27  are joined by the laser welding, and the second substrate  28   b  on which the flow path pipe SI 1  having a large sectional area is formed and the first substrate  27  are joined by an adhesive or the like, it is possible to reduce welding unevenness due to the laser welding. 
     In addition, since the filter F interposed between two second substrates  28   a  and  28   b  is provided on the first substrate  27  nipped between the second substrates  28   a  and  28   b , compared to a case where the filter F is provided on any of two second substrates  28   a  and  28   b , it is not necessary to dispose the filter F not to overlap in the radiation direction of the laser light. Therefore, it is possible to improve the degree of freedom of the design, such as the disposition or the size of the filter F. 
     In addition, as the inclined surface is formed on the wall surfaces of the end portions  273   a  and  273   b  of the flow path PI 1 , and an enlarged diameter portion  284  having an inclined surface in a tapered shape which widens to the downstream side is formed in the outlet flow path H 2  of the end portions  273   a  and  273   b , it is possible to suppress the stagnation of the ink in the end portions  273   a  and  273   b  of the flow path PI 1 , and to improve the discharge performance of the bubbles which stay at the stagnation part. As illustrated in  FIG. 14 , on the wall surfaces of the end portions  273   a  and  273   b , the plurality of inclined surfaces may be formed and the inclined surfaces may be joined, or one inclined surface may be formed. Each of the inclined surfaces of the enlarged diameter portion  284  is configured to be joined to the inclined surfaces of the wall surfaces of the end portions  273   a  and  273   b  by the welding surface Wa. A shape of the end portions  273   a  and  273   b  and the enlarged diameter portion  284  of the flow path PI 1  will be described in more detail by a second embodiment. 
     Flow Path Structure in Second Embodiment 
     Next, the flow path structure G 1  in the second embodiment will be described. In the first embodiment, the flow path structure G 1  which can improve the air tightness of the first flow path formed to be surrounded by the welding surface by reducing welding unevenness, in the laser welding with respect to the substrate on which the flow path pipe is projected, will be described. In the second embodiment, the flow path structure G 1  which can improve the bubbles discharge performance by suppressing the stagnation of the ink at the branch point, in the flow path structure provided with the second flow path that branches from the first flow path, in the first flow path in which the liquid flows, will be described. 
       FIG. 15  is a sectional view illustrating a configuration of the flow path structure G 1  in the second embodiment.  FIG. 15  corresponds to  FIG. 10 , and is a partial sectional view of one system taken along line X-X when the configuration of the second embodiment is employed in the flow path PI 1  of the ink I of four systems of the flow path structure G 1  illustrated in  FIG. 7 .  FIG. 16  is a side view and a plan view of a case where the first substrate  27  and the second substrate  28  which configure a part of the flow path structure G 1  illustrated in  FIG. 15  are exploded, and corresponds to  FIG. 11 .  FIG. 17  is a sectional perspective view taken along line XVII-XVII illustrated in  FIG. 15 , and corresponds to  FIG. 9 . 
     The flow path structure G 1  of the second embodiment is a structure which has further devised the flow path structure of the flow path PI 1  of the liquid of four systems in the first embodiment. Therefore, the part having functions similar to those of the flow path structure G 1  of the first embodiment will be given the same reference numerals in  FIGS. 15 to 17 , and the specific description thereof will be omitted. 
     The flow path structure of the second embodiment illustrated in  FIG. 15  is different from the flow path structure of the first embodiment illustrated in  FIG. 10  in that an inclined surface TP 1  on the flow path PI 1  side illustrated in  FIG. 17  and a tapered portion TD 1  on the outlet flow path H 2  side which are inclined in the direction of the flow of the flow path PI 1 , are formed in both of the end portions  273   a  and  273   b  of the flow path (first flow path) PI 1 , and at each branch point of the flow path PI 1  and the outlet flow path (second flow path) H 2 . 
     In the flow path PI 1  illustrated in  FIG. 15 , similar to the flow path PI 1  illustrated in  FIG. 10 , since the outlet flow paths H 2  are respectively disposed in each of both of the end portions  273   a  and  273   b  of the flow path PI 1 , and four outlet flow paths H 2  are disposed between both of the end portions  273   a  and  273   b  of the flow path PI 1 , there are four branch points of the flow path PI 1  and the outlet flow path H 2 . 
     Since the inlet flow path H 1  is disposed on a side opposite to the outlet flow path H 2  between both of the end portions  273   a  and  273   b  of the flow path PI 1 , the flow of the ink in the flow path PI 1  is as follows. In other words, the ink which flows toward one end portion  273   a  of the flow path PI 1  branches and is discharged respectively to the outlet flow path H 2  of the end portion  273   a , and to one outlet flow path H 2  between the end portion  273   a  and the inlet flow path H 1 . The ink which flows toward the other end portion  273   b  of the flow path PI 1  branches and is discharged respectively to the outlet flow path H 2  of the end portion  273   b , and to three outlet flow paths H 2  between the end portion  273   b  and the inlet flow path H 1 . In the second embodiment, the inclined surface TP 1  on the above-described flow path PI 1  and the tapered portion TD 1  on the outlet flow path H 2  side are formed in both of the end portions  273   a  and  273   b  of the flow path PI 1  and at branch point of four outlet flow paths H 2 . 
     Hereinafter, a configuration example of the inclined surface TP 1  on the flow path PI 1  side and the tapered portion TD 1  on the outlet flow path H 2  side will be described. First, the inclined surface TP 1  on the flow path PI 1  side will be described. As illustrated in  FIGS. 15 and 16 , at branch point of the end portions  273   a  and  273   b  of the flow path PI 1 , the inclined surface TP 1  is formed on the wall surface of each of the end portions  273   a  and  273   b.    
     Meanwhile, in each of four branch points between both of the end portions  273   a  and  273   b  of the flow path PI 1 , a projection portion  274  which protrudes toward the outlet flow path H 2  from a part which opposes the outlet flow path H 2  in the flow path PI 1 , is formed, and the inclined surface TP 1  is formed on the wall surface on the upstream side of the projection portion  274 . The inclined surface TP 1  is inclined so that the height of the projection portion  274  increases toward the downstream side, with respect to the direction of the flow in the flow path PI 1 . In addition, the height of the projection portion  274  will be described later in detail. 
     In each projection portion  274 , an inclined surface TP 2  is also formed on the wall surface on the downstream side. The inclined surface TP 2  is inclined on a side opposite to the inclined surface TP 1 , with respect to the direction of the flow in the first flow path. In other words, the inclined surface TP 2  is inclined so that the height of the projection portion  274  decreases toward the downstream side. In this manner, as the inclined surface TP 2  is also formed on the wall surface on the downstream side of the projection portion  274 , compared to a case where the inclined surface TP 2  is not formed on the downstream side, it is possible to suppress the stagnation further on the downstream side than the projection portion  274  in the flow path PI 1 . 
     Next, the tapered portion TD 1  on the outlet flow path H 2  side will be described. On each of six outlet flow paths H 2 , the enlarged diameter portion  284  is formed at a part opened on the second opposing surface  282  of the second substrate  28 , and in the enlarged diameter portion  284 , the tapered portion TD 1  is formed to be widened in a tapered shape on the downstream side of the flow path PI 1 , toward the flow path PI 1  (toward the negative side of the Z direction). The enlarged diameter portion  284  is a path from the outlet flow path H 2  to the flow path PI 1 , and is a part at which the flow path diameter continuously increases from the outlet flow path H 2  to the flow path PI 1 . As illustrated in  FIGS. 16 and 17 , the tapered portion TD 1  is a part on the downstream side of the flow path PI 1  on an inner circumferential surface of the enlarged diameter portion  284 , and has a shape which is a half of a conical surface that gradually widens toward the second opposing surface  282  which opposes the first substrate  27 . Since the enlarged diameter portion  284  of the outlet flow path H 2  is opened to the second opposing surface  282  which opposes the first substrate  27  in the second substrate  28 , the enlarged diameter portion  284  is likely to be formed in the outlet flow path H 2 . 
     In addition, in the second aspect, similar to the first embodiment, since the inlet flow path H 1  is disposed between both of the end portions  273   a  and  273   b  of the flow path PI 1 , the directions of the flow in the flow path PI 1  become reverse to each other between the inlet flow path H 1  and one end portion  273   a  (right side of  FIG. 15 ), and between the inlet flow path H 1  and the other end portion  273   b  (left side of  FIG. 15 ). Therefore, the disposition positions of the inclined surface TP 1  and the tapered portion TD 1  are also revere to each other on the left and right sides of  FIG. 15 . 
     A relationship between the inclined surface TP 1  and the tapered portion TD 1  is as follows. As illustrated in the enlarged view of  FIG. 15 , the inclined surface TP 1  on the upstream side of the projection portion  274  is disposed on an upper surface (a bottom surface  273   e  of the flow path groove  273 ) of the flow path PI 1  which opposes the enlarged diameter portion  284  of the outlet flow path H 2 . In addition, when drawing a virtual line y which extends along the inclination of the inclined surface TP 1  of the wall surface on the upstream side of the projection portion  274  in the sectional view of  FIG. 15 , the virtual line y passes through a region (including a boundary line between the tapered portion TD 1  and the second opposing surface  282 ) in which the tapered portion TD 1  of the enlarged diameter portion  284  is formed. According to this, at each branch point, it is possible to guide a part of the flow of the ink of the flow path PI 1 , to the tapered portion TD 1  of the enlarged diameter portion  284 , along the inclined surface TP 2  on which the wall surface on the upstream side of the projection portion  274  extends. Accordingly, since the flow of the ink of the flow path PI 1  is likely to flow to the outlet flow path H 2 , it is possible to effectively improve the discharge performance of the bubbles. 
     The inclined surface TP 1  of the end portions  273   a  and  273   b  of the flow path PI 1  has a shape similar to that of the tapered portion TD 1 , and is formed vertically reverse to the tapered portion TD 1 . In other words, the inclined surface TP 1  has a shape of a half of the conical surface which gradually widens toward the first opposing surface  272  which opposes the second substrate  28 . The first opposing surface  272  and the second opposing surface  282  are joined to each other so that a boundary line having a shape of an arc between the inclined surface TP 1  and the first opposing surface  272 , and a boundary line having a shape of an arc between the tapered portion TD 1  and the second opposing surface  282 , match each other. Accordingly, in the end portions  273   a  and  273   b  of the flow path PI 1 , since the inclined surface TP 1  and the tapered portion TD 1  communicate with each other, the flow of the ink toward the outlet flow path H 2  of the end portions  273   a  and  273   b  from the flow path PI 1  can be smoother. 
     An action effect of the flow path structure G 1  of the second embodiment will be described comparing a second comparative example.  FIG. 18  is a view which enlarges a partial section of the flow path structure G 1  in the second comparative example in which the inclined surface TP 1  and the tapered portion TD 1  are not formed, and  FIG. 19  is a view which enlarges a partial section of the flow path structure G 1  in the second embodiment in which the inclined surface TP 1  and the tapered portion TD 1  are not formed. 
     As illustrated in the second comparative example of  FIG. 18 , in a case where the inclined surface TP 1  and the tapered portion TD 1  are not formed, the stagnation of the ink is generated not only at the branch point of both of the end portions  273   a  and  273   b  of the flow path PI 1  but also at the branch point between both of the end portions  273   a  and  273   b  of the flow path PI 1 , and bubbles Bu are likely to stay. This is because the stagnation of the ink is likely to be generated at a part (upper part of the flow path PI 1  at the branch point of  FIG. 18 ) which opposes each outlet flow path H 2 , since the flow of the ink along the flow path PI 1  is pulled to the outlet flow path H 2  at each branch point. 
     Meanwhile, in the second embodiment illustrated in  FIG. 19 , in both of the end portions  273   a  and  273   b  of the flow path PI 1 , since the inclined surface TP 1  and the tapered portion TD 1  which are inclined in the direction of the flow of the flow path PI 1  are formed, the flow is formed along the inclined surface TP 1  and the tapered portion TD 1 . Furthermore, even at the branch point between the end portions  273   a  and  273   b  of the flow path PI 1 , since the inclined surface TP 1  and the tapered portion TD 1  which are inclined in the direction of the flow of the flow path PI 1 , are formed, a part of the liquid which flows in the flow path PI 1  is oriented toward the tapered portion TD 1  on the inclined surface TP 1 , and the flow along the inclined surface TP 1  and the tapered portion TD 1  is formed. Accordingly, the stagnation of the ink is suppressed not only in both of the end portions  273   a  and  273   b  of the flow path PI 1  but also at each branch point, and the bubbles are likely to be discharged from each outlet flow path H 2 . Accordingly, it is possible to improve the discharge performance of the bubbles at each branch point. 
     Furthermore, in the second embodiment, similar to the first embodiment, since the flow path pipe DI 1  is disposed to include the entire pipe surface (outer circumference) thereof, and to be included in the region of the flow path PI 1  in a plan view, it is also possible to reduce welding unevenness of the welding surface W due to the laser welding for forming the flow path PI 1 . In this manner, in the second embodiment, while improving the discharge performance of the bubbles at each branch point, it is also possible to reduce welding unevenness due to the laser welding. 
     In particular, without forming the above-described inclined surface TP 1  on the wall surfaces of the end portions  273   a  and  273   b  of the flow path PI 1 , when the pipe surface of the flow path pipe DI 1  is configured to be included in the region of each flow path PI 1 , as illustrated in  FIG. 18 , it is necessary to widen each of both of the end portions  273   a  and  273   b  of the flow path PI 1  further on the downstream side than the outlet flow path H 2  only by the pipe surface (outer circumference) of the flow path pipe DI 1 . Therefore, at a part which widens further on the downstream side than the outlet flow path H 2  in the end portions  273   a  and  273   b  of the flow path PI 1  flow path PI 1 , the stagnation of the ink is likely to be generated. At this point, since it is possible to suppress the stagnation of the ink of the end portions  273   a  and  273   b  of the flow path PI 1  by forming the above-described inclined surface TP 1  on the wall surfaces of the end portions  273   a  and  273   b  of the flow path PI 1 , it is possible to effectively improve the bubble discharge performance. 
     In addition, as illustrated in the enlarged view of  FIG. 15 , in each projection portion  274 , it is preferable that an inclination angle θP 1  of the inclined surface TP 1  on the upstream side with respect to the direction of the flow of the flow path PI 1 , is greater than an inclination angle θP 2  of the inclined surface TP 2  on the downstream side with respect to the direction of the flow of the flow path PI 1 . In this manner, the ink which flows the flow path PI 1  can be likely to flow to the outlet flow path H 2 . Accordingly, since it is possible to improve the suppression effect of the stagnation of each branch point, and the bubbles are more likely to be discharged from the outlet flow path H 2 , it is possible to further improve the discharge performance of the bubbles at each branch point. When considering this point from the inclined surface TP 2  on the downstream side of each projection portion  274 , since the inclination angle θP 2  on the inclined surface TP 2  on the upstream side is smaller than the inclination angle θP 1  on the inclined surface TP 1  on the upstream side, the flow of the ink which flows further on the downstream side than each projection portion  274  in the flow path PI 1  become smoother, and it is possible to effectively reduce the stagnation of the liquid which flows further on the downstream side than the projection portion  274 . 
     In addition, in the second embodiment, a case where both of the inclined surface TP 1  and the tapered portion TD 1  are formed at each branch point of the flow path PI 1  and the outlet flow path H 2 , is described as an example, but the invention is not limited thereto, and only one of the inclined surface TP 1  and the tapered portion TD 1  may be formed. According to this, compared to a case where the inclined surface TP 1  and the tapered portion TD 1  are not provided, since it is possible to suppress the stagnation of each branch point, it is possible to likely to discharge the bubbles. 
     In addition, the shape of the enlarged diameter portion  284  of the outlet flow path H 2  of the flow path structure G 1  is not limited to the shape illustrated in  FIG. 15 . For example, as illustrated in a modification example of  FIG. 20 , in the enlarged diameter portion  284  of the outlet flow path H 2 , when the tapered portion TD 1  which widens to the downstream side of the flow path PI 1  becomes a first tapered portion, a second tapered portion TD 2  which widens not only to the first tapered portion TD 1  but also to the opposite side, that is, the upstream side of the flow path PI 1 , may be provided. In other words, the second tapered portion TD 2  is a part on the upstream side of the flow path PI 1  on the inner circumferential surface of the enlarged diameter portion  284 , and has a shape which is a half of the conical surface which gradually widens toward the second opposing surface  282  which opposes the first substrate  27 . 
     According to this, since it is possible to enlarge the sectional area of the enlarged diameter portion  284  of the outlet flow path H 2 , it is possible to more likely to flow the ink to the outlet flow path H 2  from the flow path PI 1 . In this case, as illustrated in the enlarged view of  FIG. 20 , it is preferable that an inclination angle θD 1  of the first tapered portion TD 1  with respect to the outlet flow path H 2  becomes greater than an inclination angle θD 2  of the second tapered portion TD 2 . Accordingly, compared to a case where the inclination angle θD 1  of the first tapered portion TD 1  and the inclination angle θD 2  of the second tapered portion TD 2  are the same inclination angle, since it is possible to prevent the sectional area of the outlet flow path H 2  from being extremely large, it is possible to suppress deterioration of the flow velocity. In this manner, while suppressing deterioration of the flow velocity, it is possible to more likely to flow the ink to the outlet flow path H 2  from the flow path PI 1 . Therefore, it is possible to further improve the discharge performance of the bubbles. 
     In addition, in the flow path structure G 1  illustrated in  FIG. 15 , a case where the sectional area of the flow path PI 1  on the section orthogonal to the flow direction of the flow path PI 1  is the same between each branch point, is employed as an example, but the invention is not limited thereto, and the sectional area of the flow path PI 1  further on the downstream side than the projection portion  274  may be smaller than the sectional area of the flow path PI 1  further on the upstream side than the projection portion  274 . According to this, it is possible to reduce the sectional area of the flow path PI 1  between each branch point from the upstream side to the downstream side of the flow path PI 1 . 
     In a case where the sectional area of the flow path PI 1  between each branch point from the upstream side to the downstream side of the flow path PI 1  is the same, since the flow velocity of the ink which flows in the flow path PI 1  is reduced when passing through the projection portion or the branch portion, the bubble discharge performance deteriorates. Here, by reducing the sectional area of the flow path PI 1  between each branch point as described above from the upstream side to the downstream side of the flow path PI 1 , it is possible to suppress deterioration of the flow velocity further on the downstream side than the projection portion  274 . Accordingly, it is possible to improve the discharge performance of the bubbles further on the downstream side than the projection portion  274 . 
     In this case, for example, by changing the height of the flow path PI 1  or the width of the flow path PI 1  on the section orthogonal to the flow direction of the flow path PI 1 , it is possible to change the sectional area of the flow path PI 1 . Specifically, for example, another modification example of  FIG. 21  is an example in which the height of the flow path PI 1  further on the downstream side than the projection portion  274  decreases to be lower than the height of the flow path PI 1  further on the upstream side than the projection portion  274 , in the liquid path structure G 1  of  FIG. 15 . The height of the flow path PI 1  here is the height from a surface (the second opposing surface  282  of the second substrate  28  which becomes a lower surface of the flow path PI 1  illustrated in  FIG. 22  which will be described later) on the positive side in the Z direction to a surface (the bottom surface  273   e  of the flow path groove  273  which becomes an upper surface of the flow path PI 1  illustrated in  FIG. 22  which will be described later) on the negative side in the Z direction, on the inner wall surface of the space which configures the flow path PI 1  on the section along the direction of the flow in the flow path PI 1 . 
     In the flow path structure G 1  of  FIG. 21 , between the inlet flow path H 1  on the upstream side and the end portion  273   a  on the downstream side of the flow path PI 1 , the height hp 1  of the flow path PI 1  further on the downstream side than the projection portion  274  decreases to be lower than the height hp 0  of the flow path PI 1  further on the upstream side than the projection portion  274 . In addition, between the inlet flow path H 1  on the upstream side and the end portion  273   b  on the downstream side of the flow path PI 1 , from the upstream side to the downstream side, the height of the flow path PI 1  between each projection portion  274  gradually decreases to be hp 0 , hp 1 , hp 2 , and hp 3  (hp 0 &gt;hp 1 &gt;hp 2 &gt;hp 3 ). According to this, from the upstream side to the downstream side of the flow path PI 1 , it is possible to reduce the sectional area of the flow path PI 1  between each branch point. Accordingly, since it is possible to suppress deterioration of the flow velocity further on the downstream side than each projection portion  274 , it is possible to improve the discharge performance of the bubbles further on the downstream side than each projection portion  274 . 
     In addition, even in the flow path structure G 1  of  FIG. 21 , similar to the first embodiment, the pipe surface (outer circumference) of the flow path pipe DI 1  of the outlet flow path H 2  is included in the region of the flow path PI 1  surrounded by the welding surface. Accordingly, similar to the first embodiment, since it is possible to make the welding surface which surrounds the flow path PI 1  not to overlap the pipe surface of the flow path pipe DI 1 , it is possible to effectively reduce welding unevenness of the welding surface formed by the laser welding. 
     Furthermore, similar to the flow path structure G 1  of  FIG. 21 , in a case where the sectional area of the flow path PI 1  is adjusted by the height of the flow path PI 1 , compared to a case where the sectional area of the flow path PI 1  is adjusted by the width of the flow path PI 1 , there is not a case where the region of the flow path PI 1  surrounded by the welding surface narrows. In a case where the width of the flow path PI 1  is adjusted, in order to make the welding surface which surrounds the flow path PI 1  not to overlap the pipe surface of the flow path pipe DI 1 , it is not necessary to adjust the size of the flow path pipe DI 1  in accordance with the width of the flow path PI 1 . At this point, according to the flow path structure G 1  of  FIG. 21 , since it is possible to adjust only the height of the flow path PI 1  without changing the width of the flow path PI 1 , the effect is large because it is not necessary to adjust the size of the flow path pipe DI 1  in accordance with the width of the flow path PI 1  in order to make the welding surface which surrounds the flow path PI 1  not to overlap the pipe surface of the flow path pipe DI 1 . 
     In addition, in a case where the sectional area of the flow path PI 1  is adjusted by the height of the flow path PI 1 , as illustrated in  FIG. 21 , the inclination of the inclined surface TP 1  on the upstream side of the projection portion  274  may change in accordance with the height of the flow path PI 1 . In  FIG. 21 , as the height of the flow path PI 1  decreases, the inclination of the inclined surface TP 1  on the upstream side of the projection portion  274  decreases. Accordingly, even when the height of the flow path PI 1  changes, for example, it is possible to adjust the virtual line y (refer to the enlarged view of the  FIG. 15 ) which extends along the inclination of the inclined surface TP 1  on the upstream side of the projection portion  274  to pass through the tapered portion TD 1  of the enlarged diameter portion  284  at all times. 
     In addition, in the flow path structure G 1  of  FIG. 21 , a case where the inclined surface TP 1  disposed at each branch point is formed on the upstream side of the projection portion  274  is employed, but the invention is not limited thereto. In a case where the height of the flow path PI 1  is adjusted between each branch point as illustrated in  FIG. 21 , since a step is formed at a part of each branch point in which the height of the flow path PI 1  changes, the inclined surface TP 1  may be formed on the wall surface on the upstream side of the step. 
     Furthermore, in the flow path structure G 1  of  FIG. 21 , a case where the height of the flow path PI 1  between each branch point is adjusted is employed as an example, but the height of the projection portion  274  may be adjusted. According to this, it is possible to suppress deterioration of the flow velocity further on the downstream side than each projection portion  274 . The height of the projection portion  274  here is the height from the forming surface (the bottom surface  273   e  of the flow path groove  273  which becomes the upper surface of the flow path PI 1  illustrated in  FIG. 22 ) of the projection portion  274  to a top portion  274   a  of the projection portion  274  on the section along the direction of the flow in the flow path PI 1 . 
     For example, the flow path structure G 1  illustrated in  FIG. 22  is a structure in which the height of the projection portion  274  of the flow path structure G 1  illustrated in  FIG. 15  changes. Specifically, the height of each projection portion  274  from the inlet flow path H 1  on the upstream side to the end portion  273   b  on the downstream side of the flow path PI 1  gradually increases to be ht 1 , ht 2 , and ht 3  (ht 1 &lt;ht 2 &lt;ht 3 ). As the height of the projection portion  274  increases, since it is possible to narrow the sectional area of the flow path PI 1  in the branch portion, it is possible to adjust the sectional area of the flow path PI 1  at each branch point to gradually decrease from the upstream side to the downstream side of the flow path PI 1 . Accordingly, since it is possible to suppress deterioration of the flow velocity further on the downstream side than each projection portion  274 , it is possible to improve the discharge performance of the bubbles further on the downstream side than each projection portion  274 . 
     However, the flow velocity of the ink which flows in the flow path PI 1  deteriorates when passing through each branch point from the upstream side to the downstream side of the flow path PI 1  as described above. Therefore, it is preferable that the height of the projection portion  274  is adjusted in accordance with the flow velocity between each branch point in the flow path PI 1 . In this case, since it is possible to suppress deterioration of the flow velocity as the height of the projection portion  274  increases, to that extent, it is possible to improve the discharge performance of the bubbles. However, when the height of the projection portion  274  becomes extremely high, since the area of the wall surface (inclined surface TP 1 ) of the projection portion  274  with which the flow of the ink in the flow path PI 1  comes into contact increases, the pressure loss increases, and on the contrary, the flow velocity deteriorates. Therefore, in suppressing the increase in the pressure loss, it is preferable to adjust the height of the projection portion  274  not to become extremely high. 
     Hereinafter, a preferable range of the height of the projection portion  274  at each branch point for achieving both the effect of improving the discharge performance of the bubbles and the effect of suppressing the increase in the pressure loss, will be described. First, it is presumed that the flow velocity between each branch point in the flow path PI 1  is the same. When the number of branch points from the upstream side to the downstream side in the flow path PI 1  is N (1≤N), the number of branches between each branch point is N+1, the flow velocity V(M) at the M-th (1≤M≤N) branch point from the upstream side can be expressed by the following equation (1), and a total V(M+1) of the flow velocity at the M+1-th branch point further on the downstream side than the M-th branch point can be expressed in the following equation (2).
 
 V ( M )=[1/( N+ 1)]×[( N+ 1)−( M− 1)]=( N−M+ 2)/(N+1)  (1)
 
 V ( M+ 1)=[1/( N+ 1)]×[( N+ 1)− M ]=( N−M+ 1)/( N+ 1)  (2)
 
     A ratio X of the height of the projection portion  274  with respect to the height hp of the path PI 1  in the flow path PI 1  can be expressed by the following expression (3).
 
1− V ( M )≤ X≤ 1− V ( M+ 1)  (3)
 
     When the above-described equations (1) and (2) are substituted in the above-described expression (3), the ratio X of the height of the projection portion  274  can be expressed by the following expression (4).
 
1−( N−M+ 2)/( N+ 1)≤ X≤ 1−( N−M+ 1 )/( N+ 1)  (4)
 
     A preferable range of the height of the projection portion  274  at each branch point can be calculated by the above-described expression (4). For example, in the flow path structure G 1  illustrated in  FIG. 22 , when the preferable range of the height of each projection portion  274  from the inlet flow path H 1  on the upstream side of the flow path PI 1  to the end portion  273   b  on the downstream side is calculated, the followings are achieved. First, since there are three branch points from the inlet flow path H 1  on the upstream side to the end portion  273   b  on the downstream side of the flow path PI 1 , N=3, and thus, the branch between each branch point is N+1=4. 
     Here, each of ratios X 1 , X 2 , and X 3  of the height ht 1 , ht 2 , and ht 3  of the projection portion  274  with respect to the height hp of the flow path PI 1 , are respectively expressed by the following expressions (5), (6), and (7) in which N=3 is substituted and M=1, 2, 3 is respectively substituted in the above-described expression (4).
 
0≤ X 1≤1/4  (5)
 
1/4≤ X 2≤2/4  (6)
 
2/4≤ X 1≤3/4  (7)
 
     According to this, with respect to the height hp of the flow path PI 1 , the heights ht 1 , ht 2 , and ht 3  of each projection portion  274  in the range of the above-described expressions (5), (6), and (7), are set. In this manner, by setting the height of each projection portion  274  with respect to the height hp of the flow path PI 1  within the range of the above-described expression (4), it is possible to achieve both the effect of improving the discharge performance of the bubbles and the effect of suppressing the increase in the pressure loss. 
     In addition, according to the sectional shape of the flow path PI 1 , there is a case where the sectional area of the flow path PI 1  becomes extremely small or extremely large even when the height of each projection portion  274  is the same. Therefore, accordingly, it is preferable that the height of each projection portion  274  is set within the range of the above-described expression (4).  FIG. 23  illustrates a relationship between the sectional shape of the flow path PI 1  on the section along the direction of the flow in the flow path PI 1 , and the height of the projection portion  274 . The left side of  FIG. 23  is a case where the sectional shape of the flow path PI 1  is rectangular, and the center of  FIG. 23  is a case where the sectional shape of the flow path PI 1  is a shape (a shape having a part at which the flow path width narrows upwardly) projected upwardly. The right side of  FIG. 23  is a case where the sectional shape of the flow path PI 1  is a shape (a shape having a part at which the flow path width narrows downwardly) projected downwardly. 
     For example, since the width of the flow path PI 1  becomes narrower further on the lower surface side than the upper surface side in a case (right side of  FIG. 23 ) where the sectional shape of the flow path PI 1  has a shape projected downwardly, even when the projection portion  274  having the same height is formed in a case (left side of  FIG. 23 ) where the sectional shape of the flow path PI 1  is rectangular, the sectional area of the flow path PI 1  decreases. Therefore, as illustrated in  FIG. 23 , in a case (right side of  FIG. 23 ) where the sectional shape of the flow path PI 1  is a shape projected downwardly, as the height of the projection portion  274  decrease even in a case (left side of  FIG. 23 ) where the sectional shape of the flow path PI 1  is rectangular, it is possible to ensure the sectional area of the flow path PI 1  similar to that of a case (left side of  FIG. 23 ) where the sectional shape of the flow path PI 1  is rectangular. 
     In addition, in the second embodiment, a case where the flow path groove  273  which configures the flow path PI 1  is formed only on the first substrate  27  is employed as an example, but the invention is not limited thereto, and the flow path groove  273  may be formed only on the second substrate  28 . In addition, the flow path groove which configures the flow path PI 1  may be formed on both of the first substrate  27  and the second substrate  28 , and may be joined to be accumulated by making the first substrate  27  and the second substrate  28  oppose each other so that each flow path groove opposes each other. However, in a case where the flow path groove  273  which configures the flow path PI 1  is formed only on one of the first substrate  27  and the second substrate  28 , compared to a case where the flow path groove  273  is formed on both of the first substrate  27  and the second substrate  28 , when the flow path grooves of the first substrate  27  and the second substrate  28  are accumulated to oppose each other, even when a shift between the first substrate  27  and the second substrate  28  is generated, it is possible to form a so-called first flow path. 
     The printing apparatus  100  illustrated as an example in each of the above-described aspects can be employed in various apparatuses, such as a facsimile machine or a copy machine in addition to the apparatus dedicated to the printing. Moreover, the use of the liquid ejecting apparatus of the invention is not limited to the printing. For example, the liquid ejecting apparatus which ejects a solution of a color material, is used as a manufacturing apparatus which forms a color filter of a liquid crystal display apparatus. In addition, the liquid ejecting apparatus which ejects a solution of a conductive material is used as a manufacturing apparatus which forms wiring or electrode of a wiring substrate.