Method for manufacturing liquid discharge head, liquid discharge head, and method for manufacturing liquid discharge head substrate

There is provided a method for manufacturing a liquid discharge head including a liquid discharge head substrate and a flow path forming member, the liquid discharge head substrate having a base, a pressure generation portion provided at a front surface of the base to generate pressure for discharging a liquid, and a supply port for supplying the liquid to the pressure generation portion, and the flow path forming member forming a flow path for feeding the liquid supplied from the supply port to the pressure generation portion. The method includes removing a sacrificial layer by etching the base from a back surface of the base, in a state in which an end covering portion of a cover layer for covering the sacrificial layer is covered with the resin layer. The method suppresses formation of a crack in the end covering portion that covers the end portion of the sacrificial layer.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to a method for manufacturing a liquid discharge head for discharging a liquid, a liquid discharge head, and a method for manufacturing a liquid discharge head substrate.

Description of the Related Art

An inkjet recording apparatus as a liquid discharge apparatus includes an inkjet recording head as a liquid discharge head. The inkjet recording apparatus performs recording by discharging liquid ink from the inkjet recording head, and applies the ink onto a record medium.

The liquid discharge head includes a liquid discharge head substrate (hereinafter also referred to as the substrate) and a flow path forming member. The substrate has a silicon base, a pressure generation element, and a supply port. The pressure generation element generates pressure for discharging the liquid. The supply port supplies the liquid to a pressure generation portion corresponding to the pressure generation element. The flow path forming member has a groove that forms a flow path and a discharge port. The substrate and the flow path forming member are bonded together to form a flow path for supplying the liquid to a pressure chamber containing the pressure generation portion, as well as to the pressure generation portion.

As a method for forming the supply port passing through the silicon base, a silicon anisotropic wet etching method is known. Japanese Patent Application Laid-Open No. 10-181032 discusses this type of method, which forms the supply port with high dimensional accuracy by providing a sacrificial layer on the front surface of the base. In a case where a heater is used as the pressure generation element, a heat accumulation layer for efficiently transmitting heat to the liquid is formed on the sacrificial layer. Further, a protective layer for protecting the pressure generation element from the liquid is formed on the sacrificial layer. When the supply port is formed by the anisotropic wet etching from the back surface of the base, a cover layer for covering the sacrificial layer such as the heat accumulation layer and the protective layer functions as an etching-resistant layer for stopping progress of the etching.

Meanwhile, Japanese Patent Application Laid-Open No. 2007-160624 discusses a conceivable disadvantage. Specifically, during formation of the supply port, a crack may be formed in the protective layer located in a region inside the supply port because of warpage of the base. The warpage is caused by internal stress of the flow path forming member. To prevent such a disadvantage, Japanese Patent Application Laid-Open No. 2007-160624 discusses a configuration in which the protective layer is not provided in the region inside the supply port, and an end of the protective layer and an end of the supply port are covered with an end covering layer.

In a case where the cover layer for covering the sacrificial layer such as the heat accumulation layer and the protective layer is provided, a following undesirable situation may occur. That is, in a process of removing the sacrificial layer by etching the base to form the supply port, a crack may be formed in an end covering portion of the cover layer which covers an end of the sacrificial layer.

It can be thought that the crack may be formed in the end covering portion of the cover layer for covering the heat accumulation layer and the protective layer or the like, in the following manner. When etching is performed from the back surface of the base, warpage may occur in the base because of internal stress of, for example, the heat accumulation layer, the protective layer, and the flow path forming member provided on the front surface of the base. Here, the end covering portion of the cover layer is a part that covers a step formed by the sacrificial layer, and therefore has a film thickness less than that of a part provided on a flat surface of the base. This is because, when the cover layer is provided, gas and precursor radicals if a chemical vapor deposition (CVD) method is used, or sputtered atoms if sputtering is used, become resistant to creep and adhesion in a region near the step of the sacrificial layer.

Moreover, the heat accumulation layer and the protective layer also function as the etching-resistant layer which stops the progress of the etching, for an etchant used in forming the supply port. Therefore, the etchant may change the quality of the flow path forming member, if a crack is formed in the heat accumulation layer and the protective layer in the process of forming the supply port.

SUMMARY OF THE INVENTION

The present disclosure is directed to suppression of a possibility that a crack may be formed in the end covering portion that covers the end of the sacrificial layer.

According to an aspect of the present disclosure, a method for manufacturing a liquid discharge head including a liquid discharge head substrate and a flow path forming member, the liquid discharge head substrate having a base, a pressure generation portion provided at a front surface of the base to generate pressure for discharging a liquid, and a supply port for supplying the liquid to the pressure generation portion, and the flow path forming member forming a flow path for feeding the liquid supplied from the supply port to the pressure generation portion, includes providing a sacrificial layer on the front surface of the base, providing a cover layer at the front surface of the base, the cover layer covering the sacrificial layer and including an end covering portion for covering an end of the sacrificial layer, providing a resin layer for covering the end covering portion, providing a flow path mold member on a front surface of the cover layer and a front surface of the resin layer, providing the flow path forming member on a front surface of the flow path mold member, and removing the sacrificial layer by etching the base from a back surface of the base, in a state in which the end covering portion is covered with the resin layer, wherein, in providing the resin layer, an opening which has an area smaller than an area of the sacrificial layer viewed from a direction orthogonal to the front surface of the base, is formed in the resin layer, and a surface of a part of the cover layer which covers the sacrificial layer, is exposed from the opening.

DESCRIPTION OF THE EMBODIMENTS

FIG. 11is a perspective diagram schematically illustrating a liquid discharge apparatus1(an inkjet recording apparatus) on which a liquid discharge head unit2is mounted, according to an exemplary embodiment.FIG. 12is a perspective diagram illustrating an example of the liquid discharge head unit2to be mounted on the liquid discharge apparatus1. The liquid discharge head unit2has a head housing15, an electrical connection printed board16, a flexible board13, and a liquid discharge head14. The liquid discharge head unit2is electrically connected to a main body of the liquid discharge apparatus1via the electrical connection printed board16. The electrical connection printed board16and the liquid discharge head14are electrically connected via the flexible board13. The head housing15contains a tank (not illustrated) for containing a liquid such as ink. The head housing15guides the liquid from the tank into the liquid discharge head14.

FIG. 13is a perspective diagram illustrating an example of the liquid discharge head14(an inkjet recording head) partially cut away. The liquid discharge head14has a liquid discharge head substrate10and a flow path forming member20. The liquid discharge head14has a heat application portion12(a pressure generation portion) and a discharge port21. The heat application portion12corresponds to a heater serving as a pressure generation element formed on the liquid discharge head substrate10. The heat application portion12is in contact with the liquid. The discharge port21is formed in the flow path forming member20. The discharge port21is formed at a position which corresponds to the heat application portion12, on a surface of the flow path forming member20. This surface faces a record medium. One or more discharge ports21are arranged at a predetermined pitch to form an array. Similarly, one or more heat application portions12are arranged at a predetermined pitch to form an array.

The liquid discharge head substrate10has a supply port11provided to pass through the liquid discharge head substrate10. The supply port11is provided to supply the liquid to the heat application portion12. Further, a bubble generation chamber22serving as a pressure chamber is provided to communicate with the discharge port21and to surround the heat application portion12. The bubble generation chamber22is formed by the flow path forming member20. The supply port11has an opening edge portion11ashaped like a rectangle and extended in a direction of the array of the bubble generation chambers22and the array of the discharge ports21.

The flow path forming member20and the liquid discharge head substrate10are bonded together to form a flow path23and a common liquid chamber24(seeFIGS. 1A and 1B). The flow path23communicates with each of the discharge ports21. The common liquid chamber24retains the liquid supplied from the supply port11, and distributes the liquid to the flow path23. The liquid supplied through the supply port11is supplied to the bubble generation chamber22through the common liquid chamber24and the flow path23.

Thermal energy generated by the heater is applied, via the heat application portion12, to the liquid supplied into the bubble generation chamber22. This causes film boiling, thereby generating bubbles in the bubble generation chamber22. Bubbling pressure of these bubbles increases pressure in the bubble generation chamber22. This applies kinetic energy to the liquid, so that a droplet is discharged from the discharge port21. In this process, power and a drive signal are supplied from the main body of the liquid discharge apparatus1to the heater via a connection pad17provided on the liquid discharge head substrate10, so that the heater is driven to generate the thermal energy. A dot is formed on a record medium P by discharge of a droplet from the discharge port21of the liquid discharge head14to the record medium P, so that an image is recorded on the record medium P.

A configuration of the liquid discharge head14according to a first exemplary embodiment will be described.FIGS. 1A to 1Care diagrams illustrating the liquid discharge head14according to the first exemplary embodiment.FIG. 1Ais an enlarged top view of a region A illustrated inFIG. 13.FIG. 1Bis a diagram illustrating only a section taken along a B-B line illustrated inFIG. 1A.FIG. 1Cis an enlarged view of a part near the supply port11on the front surface of the liquid discharge head substrate10illustrated inFIG. 1B.

A silicon base is used as a base10aof the liquid discharge head substrate10. A heat accumulation layer210made of a material such as silicon oxide is formed on the front surface of the base10a. Elements including a heater220made of tantalum nitride, a switching element for driving the heater220, and a selection circuit (not illustrated) are provided on the front surface of the heat accumulation layer210. The heater220is connected to a heater electrode (not illustrated). Further, a protective layer230for protecting the heater220is formed on the front surface of the heat accumulation layer210and the heater220. The protective layer230is made of a material such as silicon nitride. The flow path forming member20is formed at the front surface of the liquid discharge head substrate10, i.e., at the front surface of the protective layer230. The flow path forming member20is made of, for example, an epoxy-based resin material.

Further, an intermediate layer101is formed between the protective layer230of the liquid discharge head substrate10and the flow path forming member20. The intermediate layer101is made of a material having more strength of adhesion to (strength of bonding with) the protective layer230than that of the flow path forming member20. This can suppress peeling of the flow path forming member20off the liquid discharge head substrate (the protective layer230). The intermediate layer101may be formed of a material having the above-described characteristic. Examples of this material include resin materials such as HIMAL (produced by Hitachi Chemical Co., Ltd.) and SU-8 (produced by Kayaku MicroChem Corporation).

Furthermore, a resin layer102is provided over the opening edge portion11aof the supply port11formed on the front surface of the liquid discharge head substrate10, as illustrated inFIG. 1A. In other words, the resin layer102extends above a region inside the supply port11, when viewed from the front surface of the liquid discharge head substrate10(the surface, on which the flow path forming member20is provided, of the liquid discharge head substrate10).

The resin layer102has a part contacting the front surface of the liquid discharge head substrate10(the front surface of the protective layer230), and a part extending above the region inside the supply port11along this front surface, as illustrated inFIG. 1B. Moreover, the resin layer102has a step portion103, which is closer to the flow path forming member20than the part contacting the front surface of the protective layer230. The step portion103is formed together with an end covering portion that covers an end of a sacrificial layer310to be described below.

The resin layer102has a width of, for example, 8 μm to 12 μm. The resin layer102is provided to surround the opening edge portion11aof the supply port11. Specifically, the resin layer102has an opening having an area smaller than an opening area of the supply port11. From the viewpoint of supplying the liquid, a width W1of a part which is located inside the supply port11, of the resin layer102is desirably about 1/30 to 1/200 of an opening width W2of the supply port11.

Next, a method for manufacturing the liquid discharge head14will be described with reference toFIGS. 2A to 2DthroughFIGS. 8A to 8D.FIGS. 2A, 3A, 4A, 5A, 6A, 7A, and 8Aare diagrams each illustrating the region A illustrated inFIG. 13, when viewed from the front surface side of the liquid discharge head14. The region A is partially transparent.FIGS. 2B, 3B, 4B, 5B, 6B, 7B, and 8Bare diagrams each illustrating the liquid discharge head14when viewed from the back surface side of the liquid discharge head substrate10.FIGS. 2C, 3C, 4C, 5C, 6C, 7C, and8C are diagrams each illustrating only a section taken along a C-C line in the correspondingFIGS. 2A, 3A, 4A, 5A, 6A, 7A, and 8A.FIGS. 2D, 3D, 4D, 5D, 6D, 7D, and 8Dare diagrams each illustrating an enlarged view of a part near the supply port11of the liquid discharge head substrate10in correspondingFIGS. 2C, 3C, 4C, 5C, 6C, 7C, and 8C.

First, as illustrated inFIGS. 2A to 2D, the sacrificial layer310made of, for example, aluminum is formed by sputtering, on the front surface of the base10amade of silicon. The sacrificial layer310is configured to form the supply port11with high dimensional accuracy. The sacrificial layer310is provided at a position on the inner side of an opening region of the supply port11formed in a later process. Next, as illustrated inFIGS. 3A to 3D, the heat accumulation layer210(that has desirably a thickness of 0.5 μm to 2 μm) made of, for example, silicon oxide is formed to cover the sacrificial layer310, by a high density plasma CVD (HDP-CVD) method. Further, the heater220made of, for example, tantalum nitride is formed on the front surface of the heat accumulation layer210by sputtering. Furthermore, the protective layer230(that has desirably a thickness of 0.1 μm to 0.5 μm) made of, for example, silicon nitride is formed on the front surface of the heat accumulation layer210and the heater220, by a plasma CVD method.

A portion211of the heat accumulation layer210and a portion231of the protective layer230cover the end of the sacrificial layer310(FIG. 3D). Since the portion211and the portion231cover a step formed by the sacrificial layer310, they have a film thickness less than a part formed on a flat surface of the liquid discharge head substrate10. The heat accumulation layer210and the protective layer230each may also be referred to as a cover layer that covers the sacrificial layer310. In addition, the portion211of the heat accumulation layer210and the portion231of the protective layer230may also be referred to as the end covering portion that covers the end of the sacrificial layer310. The cover layer is formed of a material including a silicon compound.

Further, the intermediate layer101(which has desirably a thickness of 1 μm to 4 μm) made of a polyether-amide-based resin material is formed by spin coating on the front surface of the protective layer230located near the heater220. Furthermore, the resin layer102is formed to provide the step portion103that covers the portion211of the heat accumulation layer210and the portion231of the protective layer230. The intermediate layer101and the resin layer102are formed as one layer by using the same material in the same process. However, the intermediate layer101and the resin layer102may be formed using different materials. In this process, an opening104is desirably provided in the resin layer102. In this way, it becomes unnecessary to add a process of forming the opening104through which the liquid flows from the supply port11. Since the opening104is provided, the front surface of a part, which covers the sacrificial layer310, of the protective layer230is exposed from the opening104. The opening104has an area smaller than the opening area of the supply port11, and smaller than the area of the sacrificial layer310viewed from a direction orthogonal to the front surface of the liquid discharge head substrate10.

Next, a flow path mold member320made of a resist material is formed by spin coating, on the front surface of the protective layer230, the intermediate layer101, and the resin layer102, as illustrated inFIGS. 4A to 4D. Further, the flow path forming member20made of an epoxy-based resin material, for example, is formed by spin coating, on the front surface of the protective layer230and the front surface of the flow path mold member320. The flow path forming member20can be formed using a resist material having photosensitivity. Furthermore, the discharge port21is formed in the flow path forming member20through photolithography.

Next, a front surface protective layer330made of a resist material is formed by spin coating, on the front surface of the flow path forming member20and the flow path mold member320, as illustrated inFIGS. 5A to 5D. Further, a supply port forming mask layer340made of a resist material is formed by spin coating, on the back surface of the liquid discharge head substrate10.

Next, silicon anisotropic wet etching is performed using tetramethylammonium hydroxide (TMAH) from the back surface side of the base10a, by using the supply port forming mask layer340as a mask, as illustrated inFIGS. 6A to 6D. This process forms the supply port11in the base10a. The sacrificial layer310is immediately etched and thereby removed, when TMAH reaches the sacrificial layer310provided at the front surface of the liquid discharge head substrate10. This is because an etching rate of the sacrificial layer310made of aluminum is faster than that of the base10athat is a silicon base. In this process, the heat accumulation layer210also functions as an etching-resistant layer for stopping the progress of the etching in regard to TMAH.

Next, a portion located in the region inside the supply port11of the heat accumulation layer210is removed by wet etching using buffered hydrogen fluoride (BHF), as illustrated inFIGS. 7A to 7D. Further, a portion located in the region inside the supply port11of the protective layer230is removed by dry etching. In this way, the supply port11passing through the front surface and the back surface of the liquid discharge head substrate10is formed.

Next, the front surface protective layer330and the supply port forming mask layer340are removed by asking and rinsing, as illustrated inFIGS. 8A to 8D. Further, the flow path mold member320is removed by wet etching. In this way, the liquid discharge head14is formed.

Here, when the base10ais etched in the process of forming the supply port11illustrated inFIGS. 6A to 6D, warpage may occur in the base10abecause of internal stress of, for example, the heat accumulation layer210, the protective layer230, and the flow path forming member20. In the portion211of the heat accumulation layer210and the portion231of the protective layer230which cover the end of the sacrificial layer310formed in the process illustrated inFIGS. 3A to 3D, a film thickness is less than a part formed on a flat surface. Therefore, in a configuration in which the resin layer102is not provided, a crack may be formed in the portion211of the heat accumulation layer210or the portion231of the protective layer230having relatively low rigidity when the base10ais etched from the back surface. In particular, such an issue is more likely to arise if the heat accumulation layer210is formed using the HDP-CVD method to miniaturize a circuit, because the portion211of the heat accumulation layer210is formed further thinner than the part formed on the flat surface.

Therefore, as described above, the base10ais etched to form the supply port11, in a state in which the front surface side of the portion211of the heat accumulation layer210and the portion231of the protective layer230is covered by the resin layer102, as illustrated inFIGS. 6A to 6D. The portion211of the heat accumulation layer210and the portion231of the protective layer230each serving as the end covering portion are therefore reinforced by the resin layer102during the etching of the base10a. This can suppress formation of a crack. The adhering (bonding) strength of the resin layer102to the protective layer230(the cover layer) is higher than the adhering strength of the flow path mold member320to the protective layer230(the cover layer). This can provide stronger reinforcement because the resin layer102is brought into tight contact with the protective layer230, as compared with a configuration of providing the flow path mold member320on the front surface of the protective layer230with no resin layer102. The formation of a crack can be therefore suppressed.

The resin layer102is desirably formed in the same process as the process of forming the intermediate layer101disposed between the flow path forming member20and the liquid discharge head substrate10. This can suppress the formation of a crack without adding more process. Further, the heat accumulation layer210and the protective layer230can be used as an etching-resistant layer during silicon anisotropic etching, by disposing the heat accumulation layer210and the protective layer230in the region inside the supply port11.

The resin layer102can be formed thicker than the cover layer such as the heat accumulation layer210and the protective layer230. In this way, the end covering portion of the heat accumulation layer210and the protective layer230can be more firmly reinforced by using the resin layer102.

As for Japanese Patent Application Laid-Open No. 2007-160624, in which the protective layer is not provided inside the opening region of the supply port, it may become difficult in a manufacturing process to implement the configuration discussed therein. This is because, in a case where the protective layer is formed of a material containing a silicon compound such as silicon nitride, it may become difficult to ensure a difference in etching rate between the protective layer and the base10amade of silicon, and thus process control may become difficult. In contrast, the heat accumulation layer210and the protective layer230are provided inside a region that becomes the supply port11, before the supply port11is formed. It is therefore possible to suppress the formation of the above-described crack in the cover layer while adopting a simple manufacturing method.

FIGS. 9A and 9Bare diagrams illustrating a liquid discharge head according to a second exemplary embodiment.FIG. 9Ais an enlarged top view of the region A illustrated inFIG. 13.FIG. 9Bis a diagram illustrating only a section taken along a D-D line illustrated inFIG. 9A.

The second exemplary embodiment assumes a configuration in which an intermediate layer and a resin layer are formed as one layer while using the same material. Therefore, the intermediate layer and the resin layer in the first exemplary embodiment are combined and may be referred to as an intermediate layer401. The intermediate layer401includes a part provided between the flow path forming member20and the liquid discharge head substrate (the protective layer230), a part facing the common liquid chamber24(a part of the intermediate layer401), and a part extending to the region inside the supply port11. In addition, these parts of the intermediate layer401are connected to each other. The intermediate layer401is not provided inside the bubble generation chamber22.

The intermediate layer401has a step portion402which comes close to the flow path forming member20in the region inside the supply port11. The step portion402reinforces the portion211of the heat accumulation layer210and the portion231of the protective layer230in a process of forming the supply port11. It is therefore possible to suppress the formation of a crack in these parts.

The supply port11may be formed to be a large port because of variations in a manufacturing process. This may locate the resin layer102surrounding the opening edge portion11aof the supply port11according to the first exemplary embodiment, in the region inside the supply port11of the base10a. In this case, the resin layer102may be formed to be sunk to the supply port11, if the intermediate layer101and the resin layer102are separated, i.e., not connected to each other, as in the first exemplary embodiment.

In contrast, the intermediate layer401has a part formed between the flow path forming member20and the protective layer230, and a part located in the region inside the supply port11which includes the step portion402. These parts are formed to be connected to each other. This prevents such a situation that the entire intermediate layer401is located in the region inside the supply port11even if the supply port11is formed as a large port. It is therefore possible to suppress sinking of the intermediate layer401to the supply port11due to variations in manufacturing the supply port11.

FIGS. 10A and 10Bare diagrams illustrating a liquid discharge head according to a third exemplary embodiment.FIG. 10Ais an enlarged top view of the region A illustrated inFIG. 13.FIG. 10Bis a diagram illustrating only a section taken along an E-E line illustrated inFIG. 10A.

The third exemplary embodiment assumes a configuration in which an intermediate layer and a resin layer are formed as one layer using the same material. Therefore, the intermediate layer and the resin layer in the first exemplary embodiment are combined and referred to as an intermediate layer601. The intermediate layer601has a step portion602which comes close to the flow path forming member20in the region inside the supply port11. The step portion602reinforces the portion211of the heat accumulation layer210and the portion231of the protective layer230in a process of forming the supply port11. It is therefore possible to suppress the formation of a crack in these parts.

Further, as with the second exemplary embodiment, the intermediate layer601has a part provided between the flow path forming member20and the liquid discharge head substrate10(the protective layer230), a part facing the common liquid chamber24, and a part extending to the region inside the supply port11. In addition, these parts of the intermediate layer601are connected to each other. It is therefore possible to suppress sinking of the intermediate layer601to the supply port11due to variations in manufacturing the supply port11.

Here, a part of the intermediate layer601formed between the flow path forming member20and the protective layer230is referred to as a first part611. Further, a part of the intermediate layer601including the step portion602and provided over the opening edge portion11aof the supply port11is referred to as a second part612. Furthermore, a part of the intermediate layer601provided at a position facing the common liquid chamber24and connecting the first part611and the second part612is referred to as a third part613. The intermediate layer601is not provided in the bubble generation chamber22and the flow path23.

Further, the flow path forming member20has a wall25formed between the adjacent bubble generation chambers22, and between the adjacent flow paths23. The first part611is located between the wall25and the liquid discharge head substrate10. The third part613connects the first part611and the second part612along an extending direction of the wall25, as illustrated inFIG. 10A. The extending direction of the wall25is also a direction along the front surface of the liquid discharge head substrate10and intersecting with the array direction of the heat application portions12. In other words, the intermediate layer601is not provided in a part24aof the common liquid chamber24that communicates with the flow path23.

In this way, in addition to the configuration of the second exemplary embodiment, a configuration is adopted which does not provide the intermediate layer601in the part24athat communicates with the flow path23of the common liquid chamber24. This can suppress an increase in resistance to the flow from the supply port11to the bubble generation chamber22. Therefore, it is possible to ensure supply of the liquid to the bubble generation chamber22, while suppressing the sinking of the intermediate layer601to the supply port11.

In order to further suppress the increase in resistance to the flow, a width W3(a length in the array direction of the heat application portions12) of the third part613is desirably shorter than each of a width W4and a width W5of the first part611located between the wall25and the liquid discharge head substrate10.

This application claims the benefit of Japanese Patent Application No. 2016-150418, filed Jul. 29, 2016, which is hereby incorporated by reference herein in its entirety.