Liquid ejection head and method of manufacturing liquid ejection head

Provided are a liquid ejection head capable of preventing deformation and breakage of a filter and a method of manufacturing the liquid ejection head. The liquid ejection head comprises: a substrate comprising a supply port through which to supply a liquid and an element configured to produce energy for ejecting the liquid; a resin layer comprising an ejection port through which the liquid is ejectable with the energy produced by the element, and a flow channel connecting the supply port and the ejection port; a filter disposed between the supply port and the flow channel; and a support portion supporting a surface of the filter on the supply port side and a surface of the filter on the flow channel side.

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

The present disclosure relates to a liquid ejection head capable of ejecting a liquid such as ink and a method of manufacturing the liquid ejection head.

Description of the Related Art

Japanese Patent Laid-Open No. 2005-178364 discloses a technique for inkjet print heads, which eject ink, to capture dust in the ink by providing a filter comprising through-holes smaller in diameter than ink ejection ports. Specifically, the above filter is disposed between a substrate on and in which are formed heating elements and an ink supply port, and a coating resin layer in which are formed ink ejection ports and an ink channel connecting the ink ejection ports and the ink supply port, and this filter is used to capture foreign substances in the ink.

SUMMARY OF THE DISCLOSURE

In the first aspect of the present disclosure, there is provided a liquid ejection head comprising:

a substrate comprising a supply port through which to supply a liquid and an element configured to produce energy for ejecting the liquid;

a resin layer comprising an ejection port through which the liquid is ejectable with the energy produced by the element, and a flow channel connecting the supply port and the ejection port;

a filter disposed between the supply port and the flow channel; and

a support portion supporting a surface of the filter on the supply port side and a surface of the filter on the flow channel side.

In the second aspect of the present disclosure, there is provided a method of manufacturing a liquid ejection head comprising:

a first step of preparing a substrate comprising an element configured to produce energy for ejecting a liquid;

a second step of forming a filter on a first surface of the substrate, the filter comprising a plurality of through-holes;

a third step of forming a hole portion in the filter;

a fourth step of forming a supply port in the substrate such that the supply port communicates with the hole portion, and filling a filling member into the supply port;

a fifth step of

forming a first resin layer on the filter, and

forming a first pattern for forming a support portion by using the hole portion and shaping the first resin layer and the filling member, the support portion being a portion that supports both a surface of the filter on the supply port side and a surface of the filter opposed to the surface; and

a sixth step of

forming a second resin layer by covering the first resin layer with a resin material and causing the resin material to flow into the first pattern,

forming an ejection port through which to eject the liquid in the second resin layer at a position aligned with the element, and

forming the support portion by removing the first resin layer and the filling member.

DESCRIPTION OF THE EMBODIMENTS

In such an inkjet print head, the loss of pressure on the ink passing through the filter needs to be reduced in order to supply an ink amount necessary for ink ejection. To this end, the thickness of the filter may be reduced since the thickness of the filter greatly affects the pressure loss. However, reducing the film thickness of the filter decreases the mechanical strength of the filter. Consequently, the filter may possibly be deformed and broken by abrupt ink flow during capture of foreign substances in the ink and recovery actions. Meanwhile, due to the progress in printing techniques in recent years, inkjet print heads have been demanded to be longer in length and more durable. In a case where an inkjet print head is constructed to be longer in length, the area of its filter increases, thereby increasing the load on the filter and thus decreasing its durability.

Note that Japanese Patent Laid-Open No. 2005-178364 discloses a configuration in which the surface of the filter on the ink channel side is supported by a support portion in order to prevent breakage of the filter. However, the filter is supported only from above in the configuration described in Japanese Patent Laid-Open No. 2005-178364. In this case, problems such as deformation and breakage of the filter may possibly occur depending on the structure of the inkjet print head or the ink flow.

The present disclosure provides a liquid ejection head capable of preventing deformation and breakage of a filter and a method of manufacturing the liquid ejection head.

An example of a liquid ejection head and a method of manufacturing the same according to an embodiment of the present disclosure will be specifically described below with reference to the accompanying drawings.

FIG. 1Ais a plan view of the liquid ejection head.FIG. 1Bis an enlarged view of a part ofFIG. 1A.FIG. 1Cis an end view of a cross section along line IC-IC inFIG. 1B.FIG. 1Dis an end view of a cross section along line ID-ID inFIG. 1B.

A liquid ejection head10illustrated inFIG. 1Acan be used as an inkjet print head, which ejects ink, for example. The liquid ejection head10comprises a substrate12provided with ejection energy production elements11and a drive circuit (not illustrated) for driving the ejection energy production elements11. The liquid ejection head10also comprises a nozzle layer16with ejection ports14formed therein through which a liquid can be ejected, and a filter18provided between the substrate12and the nozzle layer16.

The substrate12is, for example, a wafer made of monocrystalline silicon with crystal orientation (100). The substrate12is shaped in a substantially rectangular plate shape extending in a Y direction. In the substrate12is formed a common supply port20(supply port) through which to supply the liquid to a common flow channel21. The common supply port20extends in the Y direction substantially in the center of the substrate12in an X direction, which is perpendicular to the Y direction. The common supply port20is a common port for a plurality of pressure chambers23to supply the liquid thereto through the common flow channel21. This common supply port20is formed, for example, by a method such as anisotropic etching of the monocrystalline silicon with an alkaline solution or dry etching such as plasma etching using a gas such as a fluorocarbon-based gas or a chlorine-based gas.

The ejection energy production elements11are disposed on one surface12a(first surface) of the substrate12at its opposite end portions in the X direction at certain intervals along the Y direction. Note that elements such as heating elements or piezoelectric elements can be used as the ejection energy production elements11. At least one ejection energy production element11may be provided on the substrate12in accordance with the usage of the liquid ejection head10.

The nozzle layer16(resin layer) comprises the common flow channel21, which communicates with the common supply port20, formed in the substrate12, through through-holes24(described later) formed in the filter18. The nozzle layer16also comprises the pressure chambers23, which eject the liquid from the ejection ports14by using pressure produced by the ejection energy production elements11. The pressure chambers23are provided for the ejection energy production elements11in a one-to-one correspondence. Each pressure chamber23communicates with the common flow channel21through a liquid flow channel22. In other words, in the present embodiment, the common flow channel21, the liquid flow channels22, and the pressure chambers23function as flow channels connecting the common supply port20and the ejection ports14.

In this configuration, the liquid is supplied from the common supply port20to the common flow channel21through the filter18. The liquid supplied to the common flow channel21is then supplied to each pressure chamber23through the corresponding liquid flow channel22. Then, the liquid inside the pressure chamber23receives pressure from the corresponding ejection energy production element11, so that the liquid is ejected from the corresponding ejection port14.

The filter18is a membrane filter. In the filter18are formed the plurality of through-holes24, which are smaller in diameter than the ejection ports14. For this reason, when the liquid at the common supply port20flows into the common flow channel21through the through-holes24, foreign substances in the liquid larger than the diameter of the through-holes24cannot pass through the through-holes24. As a result, these foreign substances are captured by the filter18. By changing the diameter of the through-holes24on the basis of characteristics of the liquid to be ejected or the like, it is possible to selectively capture foreign substances and hence maintain the quality of the liquid ejection.

For the constituent material of the filter18, it is possible to use an organic material or inorganic material that is highly adhesive to the substrate12and the nozzle layer16and resistant to the liquid to be ejected. Specifically, it is possible to use a photo-setting resin or a thermosetting resin, for example. As for the method of forming the filter18, it is possible to use a method such as chemical vapor deposition (CVD) or physical vapor deposition (PVD) in the case where the filter18is an inorganic film.

The method of forming the through-holes24varies depending on the constituent material of the filter18. In the case where the filter18is made, for example, of a photo-setting resin, the through-holes24are formed in the filter18by photolithography. On the other hand, in the case where the filter18is made, for example, of a resin material other than photo-setting resins, firstly a film is formed from this resin material, and an etching mask is formed on this film. Then, the through-holes24are formed by dry etching or wet etching. Further, in the case where the filter18is formed, for example, from an inorganic material or the like, the through-holes24are formed by performing laser processing or the like on the formed filter18.

As illustrated inFIG. 1D, the filter18is supported by support portions26extending from the nozzle layer16. These support portions26are made of the same material as the material of the nozzle layer16and are formed integrally with the nozzle layer16. Note that the support portions26may be made of a material different from the material of the nozzle layer16or formed as separate bodies from the nozzle layer16. The support portions26reinforce the mechanical strength of the filter18.

The support portions26are formed to extend from the nozzle layer16and penetrate through the filter18. Specifically, the support portions26are formed to extend through the common flow channel21and penetrate through the filter18and their tip portions26aare positioned inside the common supply port20. While the support portions26have a substantially cylindrical shape in the present embodiment, their shape is not limited to a substantially cylindrical shape. Two support portions26are provided spaced from each other in the X direction substantially at the center of the common supply port20in the X direction. Note that depending, for example, on the length of the common supply port20in the X direction and the diameter of the support portions26, one or three or more support portions26may be provided in the X direction substantially at the center of the common supply port20in the X direction. Also, a plurality of support portions26are provided at certain intervals in the Y direction, along which the common supply port20extends.

The tip portion26aof each support portion26is larger in diameter than a penetrating portion26bof the support portion26penetrating through the filter18. Further, the tip portion26aadheres tightly to a surface18bof the filter18in abutment with the common supply port20. Also, an extending portion26cof each support portion26positioned in the common flow channel21(in the flow channel) is larger in diameter than the penetrating portion26b. Further, the extending portion26cadheres tightly to a surface18aof the filter18in abutment with the common flow path21. With this configuration of the support portions26, the filter18is supported by the support portions26from both the surface on the common supply port20side (supply port side) and the surface on the common flow channel21side (flow channel side).

The diameters of the tip portion26a, the penetrating portion26b, and the extending portion26cmay be larger than the diameter of the through-holes24or equal to or smaller than the diameter of the through-holes24. Also, the difference in diameter between the extending portion26cand the penetrating portion26band the difference in diameter between the tip portion26aand the penetrating portion26bmay be equal to each other, or one may be larger than the other. By setting the diameters of the extending portion26cand the tip portion26arelative to the diameter of the penetrating portion26bon the basis of the mechanical strength of the filter18, it is possible to reliably improve the mechanical strength of the filter18.

The filter18is subjected to a large load due to abrupt ink flow during capture of foreign substances and recovery actions. However, the filter18is supported by the support portions26from both the surface on the common supply port20side and the surface on the common flow channel21side. For this reason, even when a large load is applied to the filter18, the filter18is prevented from being detached from the support portions26and is reliably supported by the support portions26. Accordingly, the high reinforcing effect on the filter18by the support portions26can be maintained for a long time.

FIGS. 2A to 2EandFIGS. 3A to 3Eare diagrams for explaining an example of a process of manufacturing the liquid ejection head10. Note that each ofFIGS. 2A to 2EandFIGS. 3A to 3Eis an end view of a cross section at a position at which ejection ports14, through-holes24, and support portions26are positioned along the X direction, as inFIG. 1D. Also, to facilitate the understanding, two through-holes24are provided at the above position. Further, illustration of the ejection energy production elements provided at the positions facing the ejection ports14is omitted. Furthermore, to facilitate the understanding, each constituent member is given a different pattern.

In the process of manufacturing the liquid ejection head10, first, a silicon wafer is prepared in which are formed ejection energy production elements and a drive circuit for driving the ejection energy production elements. This wafer is a wafer made of monocrystalline silicon with crystal orientation (100) and measuring 200 mm in diameter and 725 μm in thickness (length in a Z direction), for example. Note that since this wafer will be the substrate12, the wafer will be referred to as the substrate12as appropriate in the following description. Then, as illustrated inFIG. 2A, a resin layer, made of a resin material, is formed on the one surface12aof the substrate12by spin coating. Note that the one surface12ais a (100) plane. Also, since this resin layer will be the filter18, the resin layer will be referred to as the filter18as appropriate in the following description. In one specific example, HL-1200CH (manufactured by Hitachi Chemical Co., Ltd.) is used as the resin material, and the number of spins is adjusted such that the film thickness of the filter18, which is the resin layer, is 3 μm.

Thereafter, an etching mask is formed on the filter18by using a positive photoresist. For example, first, a positive photoresist PMER (manufactured by TOKYO OHKAKOGYO CO., LTD.) is applied onto the filter18by spin coating to form a coating film with a film thickness of 10 μm on the filter18(on the filter). Then, proximity exposure is performed on the formed coating film by using a mask pattern in which the through-holes24are depicted, and an etching mask is formed by using a 2.38% tetramethylammonium hydroxide (TMAH) aqueous solution. Then, the through-holes24are formed by reactive ion etching (RIE) mainly using a fluorocarbon-based gas (seeFIG. 2B). Specifically, the through-holes24are formed by using a mixture gas of a fluorocarbon-based gas CF4 and oxygen, and the etching mask is stripped off by using a stripping liquid.

After forming the through-holes24in the filter18, a penetrating pattern30is formed which penetrates through the substrate12and the filter18(seeFIG. 2C). The penetrating pattern30is formed, for example, by applying a Nd-YAG laser beam from the other surface12b(second surface) of the substrate12. Note that a general silicon processing method may be used as the method of forming the penetrating pattern30. For example, semiconductor dry etching, such as RIE, can be used instead.

After forming the penetrating pattern30, the common supply port20is formed in the substrate12(seeFIG. 2D). For example, the common supply port20is formed in the substrate12by anisotropic etching of the monocrystalline silicon with a hot alkaline aqueous solution. For example, an aqueous solution of TMAH at a mass concentration of 25% heated to 80° C. is used as the hot alkaline aqueous solution, and the etching duration is approximately 4 hours. An aqueous solution such as a KOH aqueous solution or a NaOH aqueous solution may be used as the hot alkaline aqueous solution if alkali metal contamination or the like is unlikely. Note that a coating film is provided on the substrate12to protect the element portions of the substrate12during the anisotropic etching. For example, a negative photoresist OMR (manufactured by TOKYO OHKA KOGYO CO., LTD.) is applied to a thickness of 30 μm. After the anisotropic etching, the coating film, which is no longer needed, is removed by dissolving it with xylene or the like.

In the present embodiment, the penetrating pattern30is formed prior to the anisotropic etching for forming the common supply port20. In this way, the area of contact between the substrate12and the hot alkaline aqueous solution is larger, thereby shortening the duration of the etching of the substrate12with the etching solution (hot alkaline aqueous solution). Note that the method of forming the common supply port20may be such that only hole portions34(described later) are formed, a metal mask or the like is formed on the other surface12bof the substrate12, and the common supply port20is formed only by etching with an etching solution.

Next, as illustrated inFIG. 2E, a filling member32is filled in the common supply port20. In this step, the filling member32is caused to flow into neither the through-holes24nor the hole portions34, formed by the formation of the penetrating pattern30. The filling member32is formed by using, for example, a polyvinyl alcohol (PVA) aqueous solution with 3000 cp. A dispensing method can be used to fill the filling member32into the common supply port20. After the filling, a baking process is performed on the filling member32under a condition of, for example, a temperature of 90° C. and a duration of 3 minutes to vaporize moisture and thereby cure the PVA. The thickness (length in the Z direction) of the cured filling member32in the common supply port20is, for example, 100 μm. Note that the thickness of the cured filling member32may be less than 100 μm or more than 100 μm.

As illustrated inFIG. 3A, after the filling member32is filled, a resin layer36(first resin layer), made of a resin material, is formed on the filter18by spin coating. Specifically, for example, a positive photoresist ODUR (manufactured by TOKYO OHKA KOGYO CO., LTD.) is used as the resin material, and the number of spins is adjusted such that the film thickness of the resin layer36on the filter18is 17 μm. Then, a baking process is performed on the resin layer36under a condition of a temperature of 100° C. and a duration of 3 minutes.

Thereafter, as illustrated inFIG. 3B, by using photolithography, the resin layer36is left to form a pattern28(second pattern) of the common flow channel21, the liquid flow channels22, and the pressure chambers23, and is removed to form a pattern29(first pattern) of the support portions26(penetrating portion26band extending portion26c). Specifically, since the liquid flow channels22communicate with the through-holes24, the resin layer36(pattern28) is left in the through-holes24as well. Also, the resin layer36in and on the hole portions34is removed, so that the hole portions34and the remaining resin layer36form spaces (pattern29). In the pattern29of each support portion26, a substantially cylindrical space S larger in diameter than the hole portion34is formed on the hole portion34so that the penetrating portion26b, which will be positioned in the hole portion34, will be larger in diameter than the extending portion26c, which will be positioned in the common flow channel21.

After the patterns28and29are formed, a further baking process is performed on the filling member32under a condition of, for example, a temperature of 120° C. and a duration of 3 minutes. As a result, the moisture in the filling member32, i.e., the PVA, is further vaporized. As the moisture is further vaporized, the filling member32shrinks, so that, as illustrated inFIG. 3C, the regions in the filling member32in abutment with the hole portions34are indented to the common supply port20side, thereby forming recessed portions38. Here, the diameter of the recessed portions38at a surface32aof the filling member32tightly adhering to the filter18is larger than the diameter of the hole portions34. These recessed portions38serve as a pattern of the tip portions26aof the support portions26. In other words, the pattern29for forming the support portions26is formed by using the hole portions34and shaping the resin layer36and the filling member32. Note that the method of forming the recessed portions38can be changed as appropriate according to the constituent material of the filling member32. For example, the recessed portions38may be formed by a method such as wet etching or dry etching.

As illustrated inFIG. 3D, after the recessed portions38are formed, a resin layer, made of a resin material, is formed on the filter18by spin coating. In forming this resin layer, its resin material covers the pattern28and flows into the pattern29(including the recessed portions38). Note that since this resin layer (second resin layer) will be the nozzle layer16, the resin layer will be referred to as the nozzle layer16as appropriate in the following description. Specifically, for example, a negative photoresist SU-8 (manufactured by Kayaku MicroChem Corporation) is used as the resin material, and the number of spins is adjusted such that the film thickness of the nozzle layer16, which is the resin layer, is 30 μm (the film thickness on the filter18).

Then, a pre-baking process is performed on the nozzle layer16under a condition of, for example, a temperature of 90° C. and a duration of 5 minutes. Further, by using photolithography, the ejection ports14are formed so as to reach the pattern28at positions aligned with the ejection energy production elements11. Then, a post-baking process is performed on the nozzle layer16under a condition of, for example, a temperature of 140° C. and a duration of 60 minutes. Thereafter, the pattern28and the filling member32are removed by using a processing liquid (seeFIG. 3E). As a result, the nozzle layer16, comprising the support portions26, the common flow channel21, the liquid flow channels22, and the pressure chambers23, is formed. Since the nozzle layer16and the support portions26are formed together by using photolithography, the position of the formed support portions26are accurate. Note that the nozzle layer16and the support portions26may be formed separately.

As described above, in the configuration of the liquid ejection head10, in which the substrate12and the nozzle layer16adhere tightly to each other with the filter18therebetween, the support portions26, supporting the filter18, extend from the nozzle layer16and penetrate through the filter18. Also, in each support portion26, the penetrating portion26b, penetrating through the filter18, is smaller in diameter than the tip portion26aand the extending portion26c. In this way, the filter18is supported by the support portions26from both the surface on the common supply port20side and the surface on the common flow channel21side. Hence, the filter18is supported reliably as compared to the technique disclosed in Japanese Patent Laid-Open No. 2005-178364.

For this reason, in the liquid ejection head10, the support portions26can prevent movement of the filter18due to ink flow even in the case where the mechanical strength of the filter18decreases due to reduction in its film thickness and the load on the filter18increases due to increase in length of the liquid ejection head10. Accordingly, it is possible to achieve stable ejection performance and prevent deformation and breakage of the filter.

This application claims the benefit of Japanese Patent Application No. 2018-127514, filed Jul. 4, 2018, which is hereby incorporated by reference wherein in its entirety.