Ink jet recording head having structural members in ink supply port

An ink jet recording head has sufficient and uniform ink refill for all orifices and separate flow paths even though the substrate has high rigidity by dividing a supply port into a plurality of ports. The substrate of the ink jet recording head has a plurality of separate flow paths corresponding to discharge pressure generating elements, a common flow path communicating with the separate flow paths, an ink supply port communicating with the common flow path and supplying ink to the common flow path, and a plurality of beam portions dividing the ink supply port. A recess is formed on the common flow path, extending to the separate flow paths formed nearest to the beam portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink jet recording head for recording data by discharging ink and a manufacture method for the ink jet recording head.

2. Related Background Art

As an ink jet recording head to be used for an ink jet recording system for recording data by discharging ink, a so-called “side shooter type recording head” is known which discharges an ink droplet along a direction perpendicular to a substrate formed with ink discharge energy generating elements.

As a liquid discharge method for this recording head, the specification of U.S. Pat. No. 6,155,673 discloses the structure that an ink droplet is discharged when a bubble formed by heating a heat generating resistor member communicates with external air. According to this discharge method, small droplet recording can be realized easily and recent high precision recording requirements are satisfied.

The structure of a “side shooter type recording head” is known by which ink is supplied from the bottom of a substrate to discharge pressure generating elements via a supply port and a common flow path and separate flow paths. As a manufacture method for an ink jet recording head having this structure, for example, the specification of U.S. Pat. No. 6,139,761 discloses a method of forming an ink supply port in a device substrate by anisotropical etching.

Recent needs are to develop a head which has a long train of orifices and can draw a large area at one scan. As the orifice train is elongated, the ink supply port becomes long correspondingly. As the ink supply port is simply elongated as a through hole formed through a device substrate, rigidity of the device substrate is lowered considerably. As the rigidity of the device substrate lowers, there is a risk of breaking the substrate during manufacture of an ink jet recording head and influencing a manufacture yield. In order to raise the rigidity of a device substrate, the size of the device substrate may be increased. However, a large substrate size reduces the number of heads to be manufactured from one wafer, resulting in a cost increase.

Japanese Patent Application Laid-open No. 2003-039692 discloses the structure that an ink supply port is divided into a plurality of ports by using beams.FIG. 8Ais a partially transmissive plan view showing an example of an ink jet recording head with a plurality of divided ink supply ports,FIG. 8Bis a cross sectional view taken along line8B-8B ofFIG. 8A,FIG. 8Cis a cross sectional view taken along line8C-8C ofFIG. 8A, andFIG. 8Dis a cross sectional view taken along line8D-8D ofFIG. 8A. An ink jet recording head300shown inFIGS. 8A,8B,8C and8D has the structure that a plurality of beam portions311aare formed in a single, long ink supply port311formed in a substrate301, and this structure is very effective for retaining the rigidity of the substrate301. However, as the ink supply port311is divided by the beam portions311a, a separate flow path306(communicating with a common flow path308and corresponding to each discharge pressure generating element305) positioned between ink supply ports311, i.e., near at the beam portion311ahas an insufficient ink supply, so that ink refill is delayed more than other separate flow paths306formed at positions remote from the beam portion311a.

Japanese Patent Application Laid-open No. H06-115075 proposes that a bottom region of a common flow path on the surface of a substrate is etched widely to form a groove and a supply port communicating with the groove is formed. With this groove, it is expected that the supply port can be shortened and the supply port can be broadened correspondingly to improve ink refill for all separate flow paths and that a difference between ink refill due to a different relative position to the supply port can be relaxed. With this method, it is necessary to form a deeper groove in order to sufficiently relax the ink refill difference. However, as the groove is formed deeper in a wide region, the strength and rigidity of the substrate are lowered. The lowered strength of the substrate may cause breakage of the head during manufacture processes, resulting in a degraded yield. As the substrate rigidity is lowered, deformation of the substrate becomes large during manufacture processes or in use, so that ink discharge directions vary among orifices and the image quality is degraded.

In order to form a supply port at a good precision, the supply port is formed in some cases by dry etching such as reactive ion etching (RIE). Generally, although dry etching provides a high precision, it has disadvantage in terms of tact as compared to other etching processes because of single wafer processing and a low etching rate. In order to overcome the disadvantages, a substrate as thin as possible, to the extent that the strength and rigidity of the substrate are ensured, is prepared, or a substrate is thinned by grinding, wet etching or the like having a high processing performance. Thereafter, the supply port is formed by dry etching. In this case, if a groove is formed in a wide range on the bottom of the common flow path, the groove cannot be sufficiently deep in order to maintain the strength and rigidity of the substrate, so that the advantages of the groove cannot be obtained.

This method is associated with some issue of manufacture processes. For example, a method has been proposed to set a distance between the discharge pressure generating element and an orifice at a high precision and with good reproductivity by forming a flow path mold, a flow path wall and an orifice plate by solvent coating. However, if solvent coating is performed after the groove is formed deeply in a wide range of the substrate, the flow path mold and orifice plate have a saucer shape tracing the groove shape. Even if the groove is formed on the substrate, the orifice plate as the ceiling of the flow path has the saucer shape in conformity with the groove, so that the expected advantages cannot be obtained.

SUMMARY OF THE INVENTION

The present invention can provide an ink jet recording head and its manufacture method in which refill is sufficient and uniform for all orifices and separate flow paths and the substrate has a high rigidity by dividing the supply port into a plurality of ports.

In order to achieve this object, an ink jet recording head of the present invention comprises:

an orifice plate having orifices for discharging ink;

a substrate having a plurality of discharge pressure generating elements for discharging ink from the orifices and an ink supply port for supplying ink to the discharge pressure generating elements;

a plurality of separate flow paths corresponding to the discharge pressure generating elements; and

a common flow path communicating with the separate flow paths and the ink supply port,

the substrate includes a plurality of beam portions formed to divide the ink supply port; and

a recess is formed in a region corresponding to the common flow path of the substrate, the recess extending to the separate flow paths formed nearest to the beam portion.

According to the ink jet recording head of the present invention, it is possible to retain a sufficient rigidity of the substrate and provide sufficient and uniform refill of each separate flow path.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

FIG. 1is a partially broken perspective view of an ink jet recording head of the first embodiment.FIG. 2Ais a partially transmissive plan view of the ink jet recording head of the first embodiment,FIG. 2Bis a cross sectional view taken along line2B-2B ofFIG. 2A,FIG. 2Cis a cross sectional view taken along line2C-2C ofFIG. 2A, andFIG. 2Dis a cross sectional view taken along line2D-2D ofFIG. 2A.

As shown inFIG. 1, an ink jet recording head100of the embodiment is constituted of a substrate1having a plurality of discharge pressure generating elements5and an orifice plate4having orifices12corresponding to the discharge pressure generating elements5. The discharge pressure generating elements5and Al wirings (not shown) for supplying an electric signal to the discharge pressure generating elements5are formed on the substrate1by film forming techniques.

Formed in the substrate1are a plurality of separate flow paths6corresponding to the discharge pressure generating elements5, a common flow path8communicating with each separate flow path6, and ink supply ports11supplying ink from an external to the common flow path8and divided by beam portions11a. A recess9is formed in a region toward the separate flow path6formed nearest to each beam portion11adividing the ink supply ports11, by etching the substrate1deeper than a common flow path bottom8aof the common flow path8. For the purposes of simplicity, inFIGS. 2A and 2D, the ink supply port11is divided into four ink supply ports11by three beam portions11a. Namely, a recess bottom9aof the recess9is made flush with a beam portion upper surface11bof the beam portion11a.

If the ink supply port11is made long, the opening becomes long so that the rigidity of the substrate1is lowered considerably. In order to retain the rigidity of the substrate1, a plurality of beam portions11aare provided, If the beam portion upper surface11bof the beam portion11ais set to the same height as that of the common flow path8, a flow of ink from the ink supply port11to each separate flow path6near the beam portion11ais influenced considerably by the beam portion11a. In order to mitigate the influence of the beam portion11aupon the ink flow, the recess9is formed for the separate flow path6, and the beam upper surface11bof the beam portion11ais set to the same height as that of the recess bottom9aof the recess9, as described above. The recess9is formed only for the separate flow path6of the beam portion11aso that reduction in the rigidity to be caused by the recess9is suppressed as much as possible.

The discharge pressure generating element5is an energy generating element for generating a discharge energy to be applied to ink. As the discharge pressure generating element5is driven to generate heat, ink on the discharge pressure generating element5is heated suddenly and voids are generated in the separate flow path6because of film boiling. A pressure generated by growth of the voids discharges ink from the orifice12.

Next, with reference toFIGS. 3A,3B,3C,3D,3E,3F,3G and3H, description will be made on a manufacture method for the ink jet recording head100of the embodiment.

A heat generating resistor member as the discharge pressure generating element5and its drive circuit are formed on a silicon substrate1by general semiconductor device manufacture processes (FIG. 3A). The surface of the substrate1on the side of the heat generating resistor member is called a top surface1band the surface opposite to the top surface1bis called a bottom surface1c.

Next, resist is coated on the top surface1bof the substrate1. By using photolithography techniques, the resist is exposed, developed and removed in an area from the position where the ink supply port11is formed to a position in front of the position where the separate flow path6is formed, near the region between the ink supply ports11, i.e., near the beam portion11a. This removed region may not be terminated at the position in front of the position where the separate flow path6is formed, but may be extended to the inside of the separate flow path6.

Next, as shown inFIG. 3B, the region where the resist was removed is etched to form a recess9. The recess9may be formed by dry etching, wet etching or physical processing such as laser processing and ion milling. For etching, an inductively coupled plasma (ICP)—reactive ion etching (RIE) etcher may be used and SF6 and C2F8 gases may be used.FIG. 3Cis a cross sectional view taken along line3C-3C ofFIG. 3B.

A silicon oxide film is formed by plasma CVD, the silicon oxide film being used as an etching stopper layer.

Next, polymethylisopropenylketone is solvent-coated, the polymethylisopropenylketone being UV resist capable of being melted at a later process. This resist is exposed to UV light and developed to form a flow path mold13(FIG. 3D).

Cation polymer type epoxy resin as negative resist is coated to form a ceiling of an ink flow path and a flow path wall partitioning each flow path. This negative resist is exposed and developed by using a photomask having a predetermined pattern to remove the negative resist in an orifice12and an electrode pad to form an orifice plate4(FIG. 3E).

Resist is coated on both the surfaces1band1cof the substrate1. The resist on the bottom surface1cis patterned by photolithography techniques, having a predetermined pattern with an opening at the position where the ink supply port11is formed. By using this resist as a mask, the ink supply port11is formed through the substrate1by dry etching (FIG. 3F). The ink supply port11may be formed by dry etching, wet etching, mechanical processing such as drill and sand blast, or physical processing such as laser processing and ion milling. Similar to the process of forming the recess9, dry etching may use an ICP-RIE etcher.FIG. 3Gis a cross sectional view taken along line3G-3G ofFIG. 3F.

The resist on both the surfaces1band1cof the substrate is removed with remover liquid. The flow path mold13is exposed via the orifice plate and immersed in methyl lactate to remove the flow path mold13and form the common flow path8and separate flow paths6corresponding to the discharge pressure generating elements5. In this case, ultrasonic waves may be applied (FIG. 3H).

Lastly, the ink jet recording head100of the embodiment is obtained by dicing the substrate.

The ink jet recording head100of the embodiment has a plurality of beam portions11ain the ink supply port11so that the rigidity of the substrate1can be retained. Further, the ink jet recording head100of the embodiment has the recess9etched deeper than the common flow path bottom8aof the common flow path8, the recess being formed only on the separate flow paths6nearest to the beam portion11acorresponding to the discharge pressure generating elements5nearest to the beam portion11a. It is therefore possible to suppress reduction in the rigidity of the substrate1. Furthermore, in the ink jet recording head100of the embodiment, the recess bottom9aof the recess9is made flush with the beam portion upper surface11bof the beam portion11a. Namely, the beam portion11amitigates the influence upon an ink flow from the ink supply port11to each separate flow path6.

As described above, the ink jet recording head100of the embodiment has the structure that the recess9is formed only on the separate flow paths6formed nearest to the beam portion11a. It is therefore possible to satisfy both suppression of reduction in the rigidity of the substrate1and sufficient and uniform ink refill of each separate flow path6.

Second Embodiment

FIG. 4Ais a partially transmissive plan view of an ink jet recording head of the second embodiment, andFIGS. 4B,4C and4D are cross sectional views thereof.FIG. 4Bis a cross sectional view taken along line4B-4B ofFIG. 4A,FIG. 4Cis a cross sectional view taken along line4C-4C ofFIG. 4A, andFIG. 4Dis a cross sectional view taken along line4D-4D ofFIG. 4A.

In the ink jet recording head101of the embodiment, the opening cross sectional shape of the ink supply port11is a parallelogram, and the beam portion11ais also a parallelogram as shown inFIG. 4A. Namely, the opening cross sectional shape of the ink supply port11is a parallelogram, and the side11dof the beam portion11ais parallel to the short side11cof the ink supply port11a. The other structures are fundamentally similar to those of the ink jet recording head100of the first embodiment, and the detailed description is omitted and similar reference symbols are used. In the second embodiment, although the opposite recesses9of the beam portion11acommunicate with two separate flow paths6, one may communicate with one separate flow path6and the other may communicate with two separate flow paths6as shown in the first embodiment.

The shape of the ink supply port11of the ink jet recording head101of the second embodiment is a parallelogram, because the layout of separate flow paths displaces by a half pitch on opposite sides of the ink supply port11. With the parallelogram arrangement, the relative positions of the discharge pressure generating element5and recess9as measured from opposite ends of the ink supply port11become the same on both sides of the ink supply port11. It is therefore possible to maintain generally the same ink flow change characteristics even if ink is discharged randomly.

Third Embodiment

FIG. 5Ais a partially transmissive plan view of an ink jet recording head of the third embodiment,FIG. 5Bis a cross sectional view taken along line5B-5B ofFIG. 5A,FIG. 5Cis a cross sectional view taken along line5C-5C ofFIG. 5A, andFIG. 5Dis a cross sectional view taken along line5D-5D ofFIG. 5A.

The ink jet recording head102of the embodiment has an orifice side beam4aat the position corresponding to the ink supply port11along a longitudinal direction of the ink supply port11. The other structures are fundamentally similar to those of the ink jet recording head101of the second embodiment, and the detailed description is omitted and similar reference symbols are used.

Generally, the orifice plate4of a side shooter type ink jet recording head floats over the ink supply port11in a wide range and the strength and rigidity of the substrate structure are weakened. In this embodiment, in order to prevent the orifice plate in the region corresponding to the ink supply port11from being floated and to retain the strength and rigidity of the ink jet recording head, the orifice side beam4ais formed on the orifice plate. The cross sectional shape of the orifice side beam4amay be any shape so long as it retains the rigidity of the orifice plate4. In this embodiment, as shown inFIG. 5B, the cross sectional shape of the orifice side beam4ain the region not corresponding to the recess9is rectangular in order to increase the cross sectional area as much as possible. On the other hand, as shown inFIG. 5C, the cross sectional shape of the orifice side beam in the region corresponding to the recess9is a smooth curved shape not hindering an ink flow in order to have a sufficient and uniform ink refill of the separate flow path6. The orifice side beam4amay gradually increase a side thickness. The orifice side beam4amay be formed not on the side facing the substrate, but on the opposite side.

The orifice side beam4acan be formed by exposing, developing and removing the region where the orifice side beam4ais formed above the ink supply port11, when the flow path mold13is patterned in the manufacture process for the ink jet recording head described with the first embodiment.

Fourth Embodiment

FIG. 6Ais a partially transmissive plan view of an ink jet recording head of the third embodiment,FIG. 6Bis a cross sectional view taken along line6B-6B ofFIG. 6A,FIG. 6Cis a cross sectional view taken along line6C-6C ofFIG. 6A, andFIG. 6Dis a cross sectional view taken along line6D-6D ofFIG. 6A.

The ink jet recording head103of the embodiment has a deep recess109having the same depth as that of the recess9of the above-described embodiments and having no step relative to the beam portion11aand a shallow recess119shallower by Δh than the deep recess109. The other structures are fundamentally similar to those of the ink jet recording head102of the third embodiment, and the detailed description is omitted and similar reference symbols are used.

Similar to each of the above-described embodiments, the deep recess109is formed extending to the separate flow paths6nearest to the beam portion11a. The shallow recess119is formed corresponding to the remaining separate flow paths6relatively remote from the beam portion11a. Namely, the shallow recess is formed extending to the separate flow paths6other than the separate flow paths6nearest to the beam portion11a. In the ink jet recording head103of the embodiment, the recess is formed for all separate flow paths6, extending to a position in front of, or inside the ink supply port11. Accordingly, not only a refill speed for all separate flow paths is improved but also a difference between ink refill characteristics of the separate flow paths6can be reduced and the uniform refill characteristics can be retained.

The deep recess109and shallow recess119having different depths can be formed by repeating resist patterning and etching a plurality of times to form recesses having desired depths. Alternatively, a so-called dual mask method may be used to conduct etching to a desired depth by using each mask.

Fifth Embodiment

FIG. 7Ais a partially transmissive plan view of an ink jet recording head of the third embodiment,FIG. 7Bis a cross sectional view taken along line7B-7B ofFIG. 7A,FIG. 7Cis a cross sectional view taken along line7C-7C ofFIG. 7A, andFIG. 7Dis a cross sectional view taken along line7D-7D ofFIG. 7A.

The ink jet recording head104of the embodiment has a long recess209having the same length as that of the recess9of the above-described embodiments and having no step relative to the beam portion11aand a short recess219shorter by ΔL than the long recess209. Namely, the short recess219is formed in the substrate1of the embodiment between the ink supply port11and separate flow paths6other than the separate flow paths6nearest to the beam portion. The short recess219is shorter by ΔL in full length than that of the long recess209. The other structures are fundamentally similar to those of the ink jet recording head102of the third embodiment, and the detailed description is omitted and similar reference symbols are used.

Similar to each of the above-described embodiments, the long recess209is formed extending to the separate flow paths6nearest to the beam portion11a. The short recess219is formed corresponding to the remaining separate flow paths6relatively remote from the beam portion11a. In the ink jet recording head104of the embodiment, the recess is formed for all separate flow paths6, extending to a position in front of, or inside the ink supply port11. Accordingly, not only a refill speed for all separate flow paths is improved but also a difference between ink refill characteristics of the separate flow paths6can be reduced and the uniform refill characteristics can be retained. Since the short recess219is shortened by ΔL than the long recess209, the thickness of the substrate is left unetched by ΔL so that the rigidity of the substrate1can be improved by an amount corresponding to the left thickness.

This application claims priority from Japanese Patent Application No. 2005-083556 filed Mar. 23, 2005, which is hereby incorporated by reference herein.