Liquid ejection head

1. A liquid ejection head comprising:

a liquid flow path having an ejection orifice; and

an energy generating element for generating energy for ejecting liquid from the flow path through the ejection orifice,

the liquid flow path and the energy generating element being formed on a first surface of a substrate having the first surface and a second surface disposed oppositely relative to each other,

the energy generating element being protected against liquid by an insulating layer formed on the first surface of the substrate,

the liquid ejection head further comprising:

a liquid inflow path running through the substrate and the insulating layer so as to allow liquid to flow into the flow path from the second surface side of the substrate; and

a liquid outflow path running through the substrate and the insulating layer so as to allow liquid to flow out from the flow path to the second surface side of the substrate,

the liquid inflow path and the liquid outflow path each respectively having a first opening formed on the first surface of the substrate after running through the substrate and a second opening formed on the insulating layer after running through the insulating layer,

the ejection orifice being arranged between the liquid inflow path and the liquid outflow path, an ejection orifice side end of the second opening being located closer to the ejection orifice than an ejection orifice side end of the first opening for each of the liquid inflow path and the liquid outflow path,

the relationships of L 1 ≥L 2 and L 3 ≥L 4 holding true, with the proviso that

L 3 >L 4 when L 1 =L 2 and L 1 >L 2 when L 3 =L 4 , where

L 1 is the distance from the center position of the ejection orifice to the ejection orifice side end of the first opening of the liquid inflow path;

L 2 is the distance from the center position of the ejection orifice to the ejection orifice side end of the first opening of the liquid outflow path;

L 3 is the distance from the center position of the ejection orifice to the ejection orifice side end of the second opening of the liquid inflow path; and

L 4 is the distance from the center position of the ejection orifice to the ejection orifice side end of the second opening of the liquid outflow path.

2. The liquid ejection head according to claim 1 , wherein an ejection orifice side wall surface of a part of the liquid inflow path and an ejection orifice side wall surface of a part of the liquid outflow path that run through the insulating layer include an inclined surface that is inclined relative to the first surface of the substrate.

3. The liquid ejection head according to claim 2 , wherein the angle formed by the ejection orifice side wall surface of at least one of the part of the liquid inflow path and the part of the liquid outflow path and the first surface of the substrate is not less than 45 degrees and less than 90 degrees.

4. The liquid ejection head according to claim 2 , wherein a flat area is formed between the bottom of the ejection orifice side wall surface and the ejection orifice side end of each of the first openings by scraping off the insulating layer.

5. The liquid ejection head according to claim 3 , wherein a flat area is formed between the bottom of the ejection orifice side wall surface and the ejection orifice side end of each of the first openings by scraping off the insulating layer.

6. The liquid ejection head according to claim 1 , wherein L 1 /L 2 is not less than 1.1 when L 1 and L 2 have a relationship of L 1 >L 2 .

7. The liquid ejection head according to claim 1 , wherein the insulating layer includes one or more electric wiring layers.

8. The liquid ejection head according to claim 1 , wherein the thickness of the insulating layer is not less than 4 μm.

9. The liquid ejection head according to claim 1 , wherein the liquid inflow path includes a first supply path having an opening on the second surface of the substrate and a plurality of second supply paths having respective openings on the first surface of the substrate and the liquid outflow path also includes a first supply path having an opening on the second surface of the substrate and a plurality of second supply paths having respective openings on the first surface of the substrate, the plurality of second supply paths being held in communication with the first supply path for each of the liquid inflow path and the liquid outflow path.

10. The liquid ejection head according to claim 9 , wherein the liquid ejection head has a plurality of ejection orifices arranged in an arrangement direction and the first supply path is formed to extend in the arrangement direction of the ejection orifices, while the second supply paths are arranged in the arrangement direction of the ejection orifices such that each of the second supply paths corresponds one or more of the ejection orifices.

11. The liquid ejection head according to claim 1 , wherein the liquid ejection head has a plurality of ejection orifices arranged in a staggered manner to form a first row and a second row and also has a group of liquid inflow paths and a group of liquid outflow paths that correspond to the first row and a group of liquid inflow paths and a group of liquid outflow paths that correspond to the second row.

12. The liquid ejection head according to claim 1 , wherein the liquid ejection head is configured such that the liquid in the flow path is made to circulate between the inside and the outside of the liquid ejection head.