Liquid discharge head

A liquid discharge head includes a substrate, a heat resistor layer, and a side wall member that forms a side wall of a pressure chamber. The heat resistor layer has a heat effect portion configured to foam liquid in an interior of the pressure chamber to discharge liquid from a discharge port. The heat effect portion is apart from the substrate, at least part of a surface of the heat resistor layer is covered with a covering layer in the interior of the pressure chamber, and the covering layer extends from the interior of the pressure chamber to a position coming into contact with the side wall of the side wall member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure relates to a liquid discharge head.

2. Description of the Related Art

Examples of known liquid discharge heads used in an inkjet type recording apparatus include a liquid discharge head having a substrate and a heat resistor layer on the substrate. The liquid discharge head having the heat resistor layer generates air bubbles in liquid in a pressure chamber by heating a heat effect portion of the heat resistor layer and discharge liquid from a discharge port.

Japanese Patent Laid-Open No. 2010-120389 discloses a liquid discharge head having the heat effect portion of a heat generating resistor formed at a position apart from the substrate. Energy generating at the heat effect portion is sufficiently transferred to liquid in a pressure chamber by forming the heat effect portion at the position away from the substrate. A schematic drawing of the liquid discharge head as described above is illustrated inFIG. 2A. A wiring2is formed on a substrate1, and an insulation layer3and a heat resistor layer5are formed thereon. A portion of the heat resistor layer5located in in a pressure chamber11corresponds to a heat effect portion. The heat effect portion is formed in a hollow shape and located at a position away from the substrate1in the pressure chamber11. A side wall of the pressure chamber11is formed of a side wall member7. InFIG. 2A, a discharge port10is also formed in the side wall member7. The discharge port10is positioned above the heat effect portion of the heat resistor layer5. A surface of the side wall member7where the discharge port10opens is covers with a surface protecting layer9. The side wall member7is formed of a film of an inorganic material, and a space formed between the side wall member7and the substrate1is filled with a filling material6.

A side wall member of the liquid discharge head described in Japanese Patent Laid-Open No. 2010-120389 is formed of an inorganic material. When the side wall member is formed of the inorganic material, the resistance characteristics of the side wall member against liquid may be improved. In addition, a reduction of the thickness of the side wall member is easily achieved.

SUMMARY OF THE INVENTION

This disclosure provides a liquid discharge head including a substrate, a heat resistor layer, and a side wall member that forms a side wall of a pressure chamber. The heat resistor layer has a heat effect portion configured to foam liquid in an interior of the pressure chamber to discharge liquid from a discharge port. The heat effect portion is apart from the substrate, at least part of a surface of the heat resistor layer is covered with a covering layer in the interior of the pressure chamber, and the covering layer extends from the interior of the pressure chamber to a position coming into contact with the side wall of the side wall member.

DESCRIPTION OF THE EMBODIMENTS

According to a study of the present inventors, when a side wall member is formed of an inorganic material, contact between the side wall member and a heat resistor layer may become insufficient in the liquid discharge head disclosed in Japanese Patent Laid-Open No. 2010-120389. In particular, if a heat effect portion of the heat resistor layer is positioned apart from a substrate, contact may occur easily between the side wall member and the heat resistor layer at a step portion of the heat resistor layer. At this time, if adhesiveness between the side wall member and the heat resistor layer is low, separation occurs therebetween, and discharge of liquid may be affected.

In view of such problems, it is an object of this disclosure to suppress separation of a side wall member which forms a side wall of a pressure chamber of a liquid discharge head in which a heat effect portion of a heat generating resistor is separated from a substrate.

FIGS. 1A and 1Bare drawings illustrating an example of a liquid discharge head of this disclosure. The liquid discharge head illustrated inFIGS. 1A and 1Bincludes a substrate1. Examples of the substrate1include a silicon substrate formed of silicon. Wiring2formed of aluminum is provided on a surface of the substrate1. When the substrate1is the silicon substrate, the surface on which the wiring2is formed is preferably (100) surface. The thickness of the wiring2preferably falls within a range from 0.4 μm to 1.5 μm.

An insulation layer such as SiO2and SiN may be formed between the surface of the substrate1and the wiring2. InFIGS. 1A and 1B, an insulation layer3is formed also on an upper surface side of the wiring2. The insulation layer3may be formed of multiple layers. Alternatively, wiring may be formed in multiple layers under the insulation layer3.

A heat resistor layer5is provided on the surface of the wiring2. The heat resistor layer5extends along the surface of the substrate1. However, the heat resistor layer5is formed at a position apart from the substrate1in a portion in the interior of a pressure chamber11. In other words, the heat resistor layer5is formed partly in a hollow shape with respect to the substrate1. A portion which is not hollow is in contact with the surface of the substrate1(or the surface of the wiring2), and is supported by the substrate1. Air bubbles are generated in liquid in part of the heat resistor layer5formed into a hollow shape with respect to the substrate1by the heat resistor layer5generating heat. This part of the heat resistor layer5is referred to as a heat effect portion5a. The heat resistor layer5is formed, for example, of TaN, TaSiN, TaAl, HfB2, TiAl, TiAlN. The thickness of the heat resistor layer5preferably falls within a range from 0.1 μm to 1.0 μm. More preferably, the thickness of the heat resistor layer5is 0.2 μm or larger. The thickness of the heat resistor layer5falls within 0.8 μm or smaller. Preferably, the heat resistor layer5has substantially the same thickness at a portion in contact with the substrate1and a portion apart from the substrate1(the heat effect portion5a) so as to have a difference within 0.1 μm. A heat resistor layer may include a plurality of layers. Examples of the layer include the layers formed of the materials described above, and, for example, a multicrystal column-shaped crystal layer.

An area of the liquid discharge head including the heat effect portion5ais referred to as the pressure chamber11. Liquid is present in the interior of the pressure chamber11. If the heat effect portion5aof the heat resistor layer5is heated, the liquid in the interior of the pressure chamber11is heated, and hence the liquid foams in the interior of the pressure chamber11. By utilizing the foam formation, the liquid is discharged from a discharge port10so as to land on a recording medium such as paper. Recording of the image or the like is performed in this manner.

The side wall of the pressure chamber11is formed of a side wall member7. The side wall member7is formed of SiC, SiN, SiCN, SiO2, Oxynitride and the like. The thickness of the side wall member7preferably falls within a range from 1.0 μm to 5.0 μm, and more preferably, 2.0 μm or larger. The thickness of the side wall member7falls within 3.0 μm or smaller.

InFIGS. 1A and 1B, the side wall member7forms the side wall of the pressure chamber11, and extends therefrom up to a surface where the discharge port10opens (opening surface), which is an upper wall of the pressure chamber. The thickness of the portion which forms the opening surface preferably has the same thickness as that of the side wall member7. In the case where the side wall and the portion which forms the opening surface are formed at once by CVD or the like, the thicknesses of these members are equal.

The opening surface is covered with a surface protecting layer9. The surface protecting layer9is formed, for example, of SiC, SiN, SiCN, SiO2, Oxynitride and the like. The thickness of the surface protecting layer9preferably falls within a range from 1.0 μm to 5.0 μm, and more preferably, 2.0 μm or smaller.

InFIGS. 1A and 1B, the side wall member7extends not only to the wall side of the pressure chamber and the opening surface of the discharge port10, but also to the outside of the pressure chamber11. The portion between the side wall member7and the substrate1includes a portion filled with a filling material6. Examples of the filling material6include resin. If an area between the pressure chamber11and a portion filled with the filling material6and an area outside the portion filled with the filling material6is remained to be a space, the strength of the liquid discharge head may be lowered. Therefore, it is preferable to fill these portions with a filling material8. Examples of the filling material8include resin. Examples of the resin as the filling material6and the filling material8include novolak resin, for example.

In the interior of the pressure chamber11, the length from the heat effect portion5ato the opening surface of the discharge port10preferably falls within a range from 3.0 μm to 5.0 μm. The length from the heat effect portion5ato the substrate1preferably falls within a range from 2.0 μm to 4.0 μm.

At least part of a surface of the heat resistor layer5is covered with a covering layer4in the interior of the pressure chamber11. The covering layer4extends from the interior of the pressure chamber11to a position coming into contact with a portion in which a side wall of the side wall member7is formed (hereinafter, referred to as the side wall). In this disclosure, with the configuration described above, the covering layer4is adhered sufficiently tightly to the side wall, and the side wall member7is prevented from being separated from the substrate1and the heat resistor layer5. With the configuration in which the covering layer4is extended not only between the heat resistor layer5and the side wall member7but also from the interior of the pressure chamber11, separation of the covering layer4itself is suppressed, whereby the separation of the side wall member7is suppressed. In particular, when the covering layer4is used as a cavitation resistant layer, the covering layer4is preferably extended in this manner.

Examples of the material that forms the covering layer4include Ta and Ir, for example. These material have high adhesiveness with respect to the side wall. In particular, in the case where the side wall is formed of inorganic material such as SiC, SiN, SiCN, SiO2, and Oxynitride, adhesiveness between the side wall and Ta or Ir is high.FIG. 1Bis an enlarged view illustrating the covering layer4in contact with the side wall. As illustrated inFIG. 1B, the surface of the heat resistor layer5is covered with the covering layer4, and the covering layer4and the side wall of the side wall member7is in contact with each other at a portion where the heat resistor layer5at an end portion of the pressure chamber11is bent toward the substrate1(step portion). In this manner, the separation of the side wall member7is suppressed by keeping the covering layer4in contact with the side wall member7. In particular, when the covering layer4is formed of SiN and the side wall member7is formed of Ta or Ir, the separation is desirably suppressed.

The covering layer4is preferably extended to a position in contact with the side wall by being extended continuously from the interior of the pressure chamber11. The covering layer4preferably extends to a substrate side along the side wall as is and extends further in a direction parallel to the surface of the substrate. Preferably, the heat resistor layer5is formed as described above, and the covering layer4is extended along the heat resistor layer5.

In contrast, in the liquid discharge head inFIG. 2A, the surface of the heat resistor layer5is not covered with the covering layer4. The step portion of the heat resistor layer5is illustrated inFIG. 2Bin an enlarged scale. InFIGS. 2A and 2B, since the covering layer4is not present, the heat resistor layer5is in contact with the side wall. For example, in the case where the heat resistor layer5is formed of Al, and is in contact with SiN which forms the side wall, separation may occur therebetween.

In this disclosure, the covering layer4may be used as a cavitation resistant layer of the heat resistor layer5. An impact of defoaming is applied to the heat effect portion5a. This is so-called cavitation and the heat effect portion5a, that is, the heat resistor layer5may become damaged. In contrast, with the presence of the covering layer4, an influence of the cavitation on the heat resistor layer5is suppressed. The covering layer4as described above may be formed of Ta preferably. Alternatively, a configuration having a plurality of layers formed of Ta and Ir is also applicable.

InFIGS. 1A and 1B, the covering layer4is formed on both surfaces of the heat resistor layer5, namely, on a surface on the discharge port10side (front surface) and on a surface on the substrate1side (back surface). However, the covering layer4may have a configuration which covers the surface of the heat resistor layer5on the discharge port side and does not cover the surface on the substrate side. Alternatively, a configuration in which the surface of the heat resistor layer5on the discharge port side is not covered, and the surface on the substrate side is covered is also possible. In the case of the configuration in which the surface of the heat resistor layer5on the discharge port side is not covered, by the surface on the substrate side is covered, the side wall member7is arranged on the surface of the heat resistor layer5on the discharge port side, that is, on a lower side. The covering layer4preferably covers both surfaces of the heat resistor layer5, namely, the surface on the discharge port side and the surface on the substrate side. At this time, the side surface of the heat resistor layer5(a surface connecting the surface on the discharge port side and the surface on the substrate side) may be or may not be covered.

The thickness of the covering layer4which is in contact with one surface of the heat resistor layer5preferably falls within a range from 0.1 μm to 1.0 μm, and more preferably, 0.2 μm or larger. The thickness of the covering layer4which is in contact with one surface of the heat resistor layer5is 0.7 μm or smaller.

In the case where the both surfaces of the heat resistor layer5are covered with the covering layers4, the thickness of the covering layer4on the front surface side of the heat resistor layer5is preferably equal to or larger than the thickness of the covering layer4on the back surface side of the heat resistor layer5. With this relationship of the thickness, the resistance characteristics against the cavitation or the adhesiveness between the heat resistor layer5and the side walls may be improved. The difference of the thickness is preferably 0.1 μm or larger, and more preferably, 0.2 μm or larger. In the case where the side surface of the heat resistor layer5is covered from the reason of manufacture, the thickness of the portion that covers the side surface is preferably the same as or similar to the thickness thereof on the front surface side with a difference not more than 0.1 μm.

It is preferable that the covering layer4and the side wall member7are in contact at a portion where the covering layer4covers the step portion of the heat resistor layer5, that is, at a portion of5binFIG. 1Afor suppressing separation of the side wall member7.

Subsequently, a method of manufacturing the liquid discharge head of this disclosure will be described with reference toFIGS. 3A to 3M.

As illustrated inFIG. 3A, a substrate1having a wiring2and an insulation layer3on the surface thereof is prepared. The substrate1is also provided with a CMOS drive transistor (not illustrated) thereon. The wiring2and the insulation layer3are formed by a spattering method or a CVD method.

Subsequently, a resist is applied on the surfaces of the wiring2and the insulation layer3on the CMOS drive transistor by spin coating. Subsequently, a flattening is performed and in addition, exposure and patterning are performed. In this manner, a first die material17, which is part of the die material of the pressure chamber is formed on the surface of the substrate1illustrated inFIG. 3B. The thickness of the first die material17preferably falls within a range from 1.0 μm to 5.0 μm. Examples of the resist include a photosensitive resin. The first die material17may be formed of a metal.

Subsequently, as illustrated inFIG. 3C, the covering layer4(hereinafter, referred to also as a “first covering layer”) is formed so as to cover the first die material17. The first covering layer4is formed by applying a material of the first covering layer4by spattering and performing patterning thereon. The first covering layer4formed here covers the back surface of the heat resistor layer (the surface of the heat resistor layer on the substrate1side).

Subsequently, as illustrated inFIG. 3D, the heat resistor layer5is formed so as to cover the first covering layer4. The wiring for heating the heat resistor layer5is also formed. These are formed by the CVD method or the patterning.

Subsequently, as illustrated inFIG. 3E, the covering layer4(hereinafter, referred to also as a “second covering layer”) is formed by spattering or patterning so as to cover the front surface of the heat resistor layer5. The second covering layer4in this case may be formed of the same material as that of the first covering layer4described in conjunction withFIG. 3C, or may be formed of a different material. In this manner, the both surfaces of the heat resistor layer5are covered with the first and second covering layers4. In the case where the back surface side is not covered, a process inFIG. 3Cneeds to be performed.

Subsequently, the resist is applied as illustrated inFIG. 3F, and patterning is performed as illustrated inFIG. 3G. Accordingly, part corresponding to the filling material6and a second die material18as part of the die material of the pressure chamber are formed on the second covering layer4. Examples of the resist include a photosensitive resin. The second die material18may be formed of a metal. The first die material17and the second die material18may be formed of the same material or may be formed of different materials.

Subsequently, as illustrated inFIG. 3H, the side wall member7is formed by the CVD method and the patterning so as to cover the filling material6and the second die material18. The side wall member7is brought into contact with the second covering layer4. Subsequently, the resist or the like is applied and flattened by spin coating or the like as illustrated inFIG. 3I, the filling material8is formed as illustrated inFIG. 3J.

As a next step, as illustrated inFIG. 3K, a surface protecting layer9is formed by the CVD method or the like so as to cover the filling material8. Subsequently, the patterning is performed on the surface protecting layer9and the side wall member7, and as illustrated inFIG. 3L, a discharge port10is formed.

Finally, the first die material17and the second die material18are removed by solvent or the like, and the liquid discharge head is manufactured as illustrated inFIG. 3M. InFIG. 3M, a supply port is not formed in the substrate1. However, the supply port may be formed after a state illustrated inFIG. 3Mand, for example, the supply port may be formed before the state ofFIG. 3Aand infilled once, and then formed again by removing the filling material.

This application claims the benefit of Japanese Patent Application No. 2014-111647, filed in May 29, 2014, which is hereby incorporated by reference herein in its entirety.