Patent Description:
As an information output device in a word processor, a personal computer, a facsimile, and the like, a recording device configured to record information on a desired character or image on a sheet-like recording medium, such as paper or a film, is commonly and widely used. In <CIT>, there is described a liquid ejection head in which a heating resistance element is used. A pair of electrical wirings is connected to the heating resistance element that is arranged on a substrate. A portion of the heating resistance element that is between the pair of electrical wirings defines an actual region of the heating resistance element. The electrical wirings are arranged on a front surface of the heating resistance element when viewed from the substrate, namely, on a surface of the heating resistance element on an ejection orifice side. The end portions of the electrical wirings have a tapered shape. In order to protect the electrical wirings and the heating resistance element from a liquid, the electrical wirings and the heating resistance element are covered by a protective film. Film boiling of the liquid, such as an ink, occurs by applying a current to the heating resistance element from the electrical wirings, which causes the heating resistance element to generate heat. The liquid is ejected from the ejection orifice as an air bubble produced by the film boiling, to thereby perform recording. With such a liquid ejection head, it is easy to densely arrange multiple ejection orifices and heating resistance elements, to thereby enable a high-resolution recording image to be obtained.

With the increase in the number of the ejection orifices and ejection speed in recent years, the power consumption of the liquid ejection head has been increasing. In order to suppress the power consumption of the liquid ejection head, it is important for the heat of the heating resistance element to be efficiently transmitted to the liquid. In order to efficiently transmit the heat, it is effective to reduce the thickness of the protective film covering the heating resistance element. Meanwhile, a certain thickness is required in order to ensure the protective performance of the protective film for the electrical wirings and the heating resistance element. In particular, as the electrical wirings are thicker than the heating resistance element, the protective film needs to be thick enough to reliably cover a step formed at a boundary portion between the electrical wirings and the heating resistance element. In the liquid ejection head described in <CIT>, the end portions of the electrical wirings have a tapered shape, and hence the coverage of the protective film is improved, with the result that the thickness of the protective film may be reduced. However, in order to realize an even thinner protective film, the taper angle of the electrical wirings needs to be reduced. However, when the taper angle is reduced, it is difficult to ensure the dimensional accuracy of the effective length of the heating resistance element defined by the end portions of the electrical wirings. When the dimension of the effective length of the heating resistance element varies, the heat-generation properties among the heating resistance elements fluctuate. Consequently, it becomes difficult to achieve high quality printing. Further prior art relating to this field can be found in document <CIT>, disclosing a recording element substrate, a method of manufacturing the recording element substrate, and a liquid ejection head. A recording element substrate according to this document includes a substrate, an insulating layer disposed on the substrate, a plurality of heating portions which are arranged on the insulating layer and which produce thermal energy used to eject a liquid, and a plurality of heat conduction members, each being located between adjacent heating portions with respect to an arrangement direction of the heating portions, the heat conduction members being located between the substrate side principal surface of the insulating layer and the heating portion side principal surface of the insulating layer and having higher thermal conductivity than the insulating layer. The heat conduction members are in contact with a heat conduction layer, which has higher thermal conductivity than the insulating layer. Further prior art can be found in document <CIT>, disclosing a CMOS/MEMS integrated ink jet print head with oxide based lateral flow nozzle architecture, and method of forming same. Further prior art can be found in document <CIT>, disclosing a recording-element substrate and a liquid ejection apparatus.

The above mentioned objects are achieved by what is defined in the appended independent claims. Advantageous modifications thereof are set forth in the appended dependent claims.

Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.

Now, with reference to the drawings, an element substrate of a liquid ejection head according to a first embodiment of the present invention is described. <FIG> is a plan view of an element substrate <NUM> of a liquid ejection head. In <FIG>, an ejection orifice forming member is not shown. <FIG> and <FIG> are enlarged schematic views of a surrounding region of one of the heating resistance elements illustrated in <FIG>. <FIG> is a plan view near the heating resistance element, and <FIG> is a cross-sectional view taken along the line 1B-1B in <FIG>. In the following description, the direction in which current flows toward the heating resistance element is referred to as a first direction X or an X direction, and the direction orthogonal to the first direction X is referred to as a second direction Y or a Y direction. The Y direction is the direction in which the heating resistance elements and the ejection orifices are arranged. The direction orthogonal to the X direction and the Y direction is referred to as a Z direction. The Z direction, which is the direction orthogonal to an ejection orifice forming surface, is the direction in which the liquid is ejected. In the embodiments of the present invention described below, an inkjet printer head configured to eject ink for printing characters is described. However, the present invention may be applied to any liquid ejection head configured to eject a liquid.

The element substrate <NUM> (<FIG>) of the liquid ejection head includes a substrate <NUM> and an ejection orifice forming member <NUM>. The substrate <NUM> includes a base material <NUM> formed of silicon and an insulating film <NUM> formed on the base material <NUM>. A heating resistance element <NUM> configured to generate heat energy for ejecting the liquid, a protective film <NUM>, and an anti-cavitation film <NUM> are arranged on the substrate <NUM>. The insulating film <NUM> is formed of an insulator, such as silicon dioxide. As illustrated in <FIG>, an ink supply port <NUM> extending in a longitudinal direction (matching the Y direction in this embodiment) is arranged in a center portion of the element substrate <NUM>. A plurality of heating resistance elements <NUM> are arranged in lines on both sides of the ink supply port <NUM>. The heating resistance elements <NUM> are formed of a tantalum compound, such as tantalum silicon nitride. The thickness (Z direction dimension) of the heating resistance elements <NUM> is from about <NUM> to about <NUM>, which is considerably smaller than the thickness of an electrical wiring <NUM>, which is described below. The ejection orifice forming member <NUM> is arranged on a surface on which the heating resistance elements <NUM> of the substrate <NUM> are formed. The ejection orifice forming member <NUM> includes ejection orifices <NUM> corresponding to respective heating resistance elements <NUM>. Together with the substrate <NUM>, the ejection orifice forming member <NUM> forms a pressure chamber <NUM> for each ejection orifice <NUM>. The pressure chambers <NUM> are in communication with the ink supply port <NUM>. Ink supplied from the ink supply port <NUM> is introduced into the pressure chambers <NUM>.

As illustrated in <FIG>, drive circuits <NUM> configured to drive the heating resistance elements <NUM> are arranged on both sides of the ink supply port <NUM> of the element substrate <NUM>. The drive circuits <NUM> are connected to electrode pads <NUM> arranged at both ends of the substrate <NUM> in the longitudinal direction Y. The drive circuits <NUM> are configured to generate a drive current of the heating resistance elements <NUM> based on a recording signal supplied from the outside of the liquid ejection head via the electrode pads <NUM>. Electrical wirings <NUM> for supplying the current to the heating resistance elements <NUM> extend into the insulating film <NUM> arranged on the substrate <NUM>. The electrical wirings <NUM> are arranged so as to be embedded in the insulating film <NUM>. The electrical wirings <NUM> electrically connect the drive circuits <NUM> and the heating resistance elements <NUM> via connecting members <NUM>, which are described later. The electrical wirings <NUM> are formed of aluminum and have a thickness (Z direction dimension) of from about <NUM> to about <NUM>. The supplied current causes the heating resistance elements <NUM> to generate heat, with the result that the heating resistance elements <NUM> becomes hot. The hot heating resistance elements <NUM> heat the ink in the pressure chambers <NUM>, causing air bubbles to form. Ink in the vicinity of the ejection orifices <NUM> is ejected from the ejection orifices <NUM> by the air bubbles to thereby perform recording.

The heating resistance elements <NUM> are covered by the protective film <NUM>. The protective film <NUM> is formed of silicon nitride, and has a thickness of from about <NUM> to about <NUM>. The protective film <NUM> may also be formed of silicon dioxide or silicon carbide. The protective film <NUM> is covered by the anti-cavitation film <NUM>. The anti-cavitation film <NUM> is formed of tantalum, and has a thickness of from about <NUM> to about <NUM>.

A plurality of connecting members <NUM> for connecting the electrical wirings <NUM> and the heating resistance elements <NUM> are arranged in the insulating film <NUM>. The plurality of connecting members <NUM> extending in the thickness direction (Z direction) are positioned so that there is a gap between adjacent connecting members <NUM> in the second direction Y. The connecting members <NUM> connect the electrical wirings <NUM> and the heating resistance elements <NUM> in the vicinity of the end portions on both sides of the heating resistance elements <NUM> in the X direction. Therefore, the current flows through the heating resistance elements <NUM> in the first direction X. Each of the plurality of connecting members <NUM> is arranged in the vicinity of the end portion of each side of the heating resistance elements <NUM> in the X direction. Each heating resistance element <NUM> includes, at one end side of the heating resistance element <NUM> and at another end side of the heating resistance element <NUM>, respectively, a connecting region <NUM> to which the plurality of connecting members <NUM> are connected. The connecting members <NUM> are a plug extending in the Z direction from near the end portions of the electrical wirings <NUM>. In this embodiment, the connecting members <NUM> have a roughly square-shaped cross-section. However, the connecting members <NUM> are not limited to having a square shape and may have a rectangular shape. The connecting members <NUM> may have rounded corners, and may have some other shape, such as a round shape or an oval shape. In this case, the connecting members <NUM> are formed of tungsten. However, the connecting members <NUM> may be formed of any one of titanium, platinum, cobalt, nickel, molybdenum, tantalum, or silicon, or of a compound of these. The connecting members <NUM> may be integrally formed with the electrical wirings <NUM>. In other words, the connecting members <NUM> may be formed integrated with the electrical wirings <NUM> by cutting a part of the electrical wirings <NUM> in the thickness direction.

The connecting regions <NUM> are the minimum rectangular region including all the connecting members <NUM> (external connecting region). The connecting regions <NUM> extend in the second direction Y, which is orthogonal to the first direction X. However, the second direction is not necessarily orthogonal to the first direction X. In other words, the connecting regions <NUM> may extend in a second direction that intersects the first direction X in a diagonal direction. The region in the heating resistance elements <NUM> actually contributing in ink foaming is called a foaming region <NUM>. The foaming region <NUM> is nearer the inner side of the heating resistance element <NUM> than the outer periphery of the heating resistance element <NUM>. A region between the foaming region <NUM> and the outer periphery of the heating resistance element <NUM> (hereinafter referred to as a "frame region <NUM>") is a region that does not contribute to ink foaming. Although heat is also generated in the frame region <NUM> when electricity is supplied, a large amount of that heat is radiated to the surroundings, and hence the ink is not foamed. The dimensions of the foaming region <NUM> in the X direction and in the Y direction are determined based on the structure of the surroundings of the heating resistance elements <NUM> and the thermal conductivity of the heating resistance elements <NUM>. The connecting regions <NUM> are arranged on both sides of the frame region <NUM>, adjacent to the foaming region <NUM> in the first direction X, and extending across a range including the entire length of the foaming region <NUM> in the second direction Y. In other words, when viewed from the first direction X, end portions 110a and 110b of both sides of the connecting regions <NUM> in the Y direction are closer to peripheral portions 101a and 101b of both sides of the heating resistance elements <NUM> in the Y direction than peripheral portions 111a and 111b of both sides of the foaming region <NUM> in the Y direction. As a result, the current density across the whole of the foaming region <NUM> is uniform.

As illustrated in <FIG>, the electrical wirings <NUM> are arranged in the insulating film <NUM>, and are connected to the heating resistance elements <NUM> by the connecting members <NUM>. Thus, the electrical connection to the heating resistance elements <NUM> is made from the back surface, and hence electrical wirings covering a front surface of the heating resistance elements <NUM> are not necessary. In a related-art configuration in which the electrical wirings are connected to the front surface of the heating resistance elements <NUM>, electrical wirings having a thickness of from about <NUM> to about <NUM> are laminated on the heating resistance elements <NUM>, and hence a comparatively thick protective film needs to be arranged in order to ensure good coverage of the steps that are about <NUM> to about <NUM> high. In contrast, in this embodiment, there is no need for electrical wirings to be arranged on the front surface of the heating resistance elements <NUM>. The thickness of the heating resistance elements <NUM> is from about <NUM> to about <NUM>, and hence the steps are considerably smaller than in the related-art configuration. Therefore, because sufficient coverage can be ensured by the protective film <NUM> having a thickness of from about <NUM> to about <NUM>, the thickness of the protective film <NUM> can be reduced, which enables a great improvement in the thermal conductivity to the ink. As a result, power consumption can be reduced, and higher image quality can be obtained due to stable foaming. Further, improvements in the patterning accuracy and reliability of the anti-cavitation film <NUM>, and improved adhesion properties of the ejection orifice forming member <NUM> to the substrate <NUM> and processing precision, can be expected. In addition, there are benefits not only in terms of improved image quality, but in manufacturing aspects as well.

The connection positions of the connecting members <NUM> to the heating resistance elements <NUM> define the actual length (effective length L) of the heating resistance elements <NUM> in the X direction (refer to <FIG>). The effective length L of the heating resistance elements <NUM> is equal to the gap of the connecting regions <NUM> on both sides in the X direction. Increasing the dimensional accuracy of the effective length L of the heating resistance elements <NUM> enables the dimensional accuracy of the length of the foaming region <NUM> in the X direction to be increased. For a related-art liquid ejection head represented by the one described in <CIT>, the shape of the heating resistance elements is typically formed by removing the electrical wirings <NUM> by wet etching, which means that it is difficult to improve the dimensional accuracy of the effective length L of the heating resistance elements <NUM>. In contrast, in this embodiment, the connecting members <NUM> are formed by forming holes in the flat insulating film <NUM> by dry etching, and embedding the material of the connecting members <NUM> in the holes. Therefore, compared with the related-art configuration, the dimensional accuracy of the effective length L of the heating resistance elements <NUM> is relatively high. The heating resistance elements <NUM> can be formed by patterning a thin film of the heating resistance elements <NUM>, which enables the dimensional accuracy of the width W of the heating resistance elements <NUM> in the Y direction to be increased. As a result of the improvement in the dimensional accuracy of the heating resistance elements <NUM>, there is less unevenness in the foaming properties among the heating resistance elements <NUM>. This not only allows the liquid ejection head to have better image quality, but extra energy that is supplied to take such unevenness into account does not need to be supplied, and hence power consumption can be reduced. Further, in the configuration according to the present invention, because the heating resistance element film is formed on a flat base layer even when the connecting members <NUM> are not embedded in holes but are directly connected to the electrical wirings <NUM> from the holes, highly reliable heating resistance elements can be formed.

In order to obtain more uniform ink ejection properties, foaming unevenness and resistance value unevenness need to be more accurate. Therefore, it is preferred that the base layer of the heating resistance elements <NUM> (lower portion region) be flat. Hitherto, it has been difficult to arrange a wiring pattern and the like directly beneath the heating resistance elements or in the vicinity thereof in a manner that avoids steps from being produced. With the configuration according to the present invention, the flatness of the electrical wirings <NUM> of each layer and the flatness of the base layer portion of the heating resistance elements <NUM> are increased by performing a treatment such as chemical mechanical planarization (CMP). As a result, as illustrated in <FIG>, an abutting surface of the connecting members <NUM> with the heating resistance elements <NUM> and an abutting surface of the insulating film <NUM> with the heating resistance elements <NUM> are arranged in the same plane. Thus, increasing the flatness of the base layer (lower portion region) of a heating resistance layer enables the electrical wirings <NUM> having a pattern for a signal wiring, a power supply wiring, and the like, to pass directly beneath the heating resistance elements <NUM> or in the vicinity thereof. Further, because a transistor may also be arranged in that region, the surface area of the element substrate <NUM> can be reduced, the cost of the liquid ejection head can be decreased, and the density of the ejection orifices <NUM> can be increased. In this embodiment, as illustrated in <FIG>, the drive circuits <NUM> and a field oxide film <NUM> are formed at a boundary region of the base material <NUM> formed of silicon with the insulating film <NUM>.

The above-mentioned configuration allows multiple layers of the electrical wirings <NUM> to be formed while suppressing effects on the properties of the heating resistance elements <NUM>. Thus, allocating a plurality of wiring layers for the electrical wirings <NUM> enables a great reduction in the power supply wiring resistance, improved power consumption, and more uniform supply of energy to the heating resistance elements <NUM>. In <FIG>, the electrical wirings <NUM> are formed in a four layer configuration. Electrical wirings 103a and 103b on a lower layer side are allocated as signal wirings and logic power supply wirings (third electrical wiring layer and fourth electrical wiring layer) for driving the heating resistance elements <NUM>. Further, electrical wirings 103c and 103d on an upper layer side are allocated as wirings for supplying current to the heating resistance elements <NUM>. In this embodiment, a ground (GNDH) wiring 103d (first electrical wiring layer) and a power supply (VH) wiring 103c (second electrical wiring layer) are both so-called solid wiring. Thus, employing a configuration (solid wiring) in which a first wiring layer and a second wiring layer of the power supply system are arranged as wiring layers formed in different layers, and both wiring layers are arranged over the whole surface of the element substrate enables the wiring resistance to be reduced to a very small value while suppressing an increase in the size of the element substrate <NUM>.

In this embodiment, the insulating film <NUM> includes four electrical wiring layers, the electrical wiring layers 103c and 103d for causing the current to flow toward the heating resistance elements <NUM>, and the electrical wiring layers 103a and 103b acting as signal wirings and logic power supply wirings for driving the heating resistance elements. The electrical wiring layers 103c and 103d are arranged closer to the heating resistance elements than the electrical wiring layers 103a and 103b. It is preferred that those wirings be thick by taking into consideration the fact that thicker wirings are relatively more efficient. Conversely, the electrical wiring layers 103a and 103b are arranged closer to the drive circuits <NUM> than the electrical wiring layers 103c and 103d. It is preferred that the thickness of those wirings be relatively thinner.

As illustrated in <FIG>, the heating resistance elements <NUM> are divided in the first direction X into two electrode regions <NUM> each including a connecting region <NUM>, and a center region <NUM> positioned between the two electrode regions <NUM>. The two electrode regions <NUM> and the center region <NUM> have the same dimension in the second direction Y. Specifically, the heating resistance elements <NUM> have a rectangular flat shape in the X-Y plane. In this embodiment, a width a of the connecting members <NUM>, a gap b of the connecting members <NUM>, and an overlap width c of the heating resistance elements <NUM> are optimized based on such a shape of the heating resistance elements <NUM>. In this case, the width a of the connecting members <NUM> is the width of the connecting members <NUM> in the Y direction, the gap b of the connecting members <NUM> is the gap in the second direction Y between adjacent connecting members <NUM>, and the overlap width c is the distance between the connecting members <NUM> at both the ends and the peripheral portions 101a and 101b of the heating resistance elements <NUM>.

It is desired that the arrangement of the connecting members <NUM> be determined based on the following formula. <MAT> where c<amin+bmin+cmin is satisfied. Each of the symbols in Formula (<NUM>) is as illustrated in <FIG>. The terms amin, bmin, and cmin, which represent the minimum dimension for the layout, depend on the performance of the manufacturing apparatus, such as deviation of the mask during patterning, etching deviation, and deviation of the connecting members <NUM>. Formula (<NUM>) shows that the maximum number n of the connecting members <NUM> is arranged based on the width W of the heating resistance elements <NUM> in the Y direction. Any remaining width is allocated to the overlap width c.

In this embodiment, in each electrode region <NUM>, the width a of each of the connecting members <NUM> is the same, each gap b is the same (the connecting members <NUM> are arranged at equidistant intervals), and each overlap width c of both sides in the Y direction is the same. Further, the width a and the gap b of the connecting members <NUM>, and the overlap width c are the same for the two electrode regions <NUM> as well. More specifically, the connecting members <NUM> of the two electrode regions <NUM> are arranged in a symmetrical shape in the Y direction. A total of lengths a of n-number of connecting members <NUM> is <NUM>% or less of the width W of the heating resistance elements <NUM> in the Y direction.

In <FIG>, a simulation result of a current density distribution in the heating resistance element <NUM> according to this embodiment is illustrated. The width of the frame region <NUM> is <NUM>. The simulation is performed by using a simulation program with integrated circuit emphasis (SPICE), in which the heating resistance elements <NUM> are modelled in a two-dimensional resistance mesh having units of <NUM> and the connecting members <NUM> are modelled in a three-dimensional mesh. The contours of the current density are shown in a range of from -<NUM>% to +<NUM>% based on the current density of the center portion of the foaming region <NUM> of the heating resistance element <NUM>. The darker sections in <FIG> represent a high current density, and the lighter sections in <FIG> represent a low current density. The effective length L of the heating resistance element <NUM> is <NUM>, the width W of the heating resistance element <NUM> in the Y direction is <NUM>, the width a of the connecting members <NUM> is <NUM>, the gap b of the connecting members <NUM> is <NUM>, and the overlap width c is <NUM>. Each width a of the connecting members <NUM>, each gap b of the connecting members <NUM>, and each overlap width c of the heating resistance element <NUM> is the same. The number n of the connecting members <NUM> is <NUM> per side.

Based on the simulation result, an improvement in the uniformity of the current distribution of the foaming region <NUM> by arranging a plurality of the connecting members <NUM> in one line is confirmed. Although there is some unevenness in the current density of the frame region <NUM> in the vicinity of the connecting members <NUM>, because this unevenness is outside the foaming region <NUM>, there is no impact on ink foaming. The current concentrates on the side of the connecting members <NUM> that face the center of the heating resistance element <NUM>. One possible method of preventing the current from concentrating may be to arrange the two lines of the connecting members <NUM> per side. However, because in such a case the current mainly flows through the line closer to the center of the heating resistance element <NUM>, there is no benefit in arranging the connecting members <NUM> in two lines unless the sheet resistance of the heating resistance element <NUM> can be reduced to a very low level. Further, with the configuration in which the current flows through two lines of connecting members <NUM>, it may be difficult define the effective length L of the heating resistance element <NUM>. Therefore, it is desired that the plurality of connecting members <NUM> be arranged in one line.

In the first embodiment, as shown by the simulation result in <FIG>, the current distribution at the four corners of the heating resistance elements <NUM> may decrease. Although this is not a problem when the width of the frame region <NUM> is as described in the first embodiment, depending on the film structure and the thermal conductivity of the heating resistance elements <NUM>, when the width of the frame region <NUM> is reduced, the decrease in the current distribution at the four corners may be a problem. In a second embodiment of the present invention, in a configuration in which a plurality of the connecting members <NUM> are arranged in one line, the uniformity of the current distribution is increased.

The arrangement of the heating resistance element <NUM> and the connecting members <NUM> according to this embodiment is illustrated in <FIG>. A relational expression is shown in Formula (<NUM>).

Each of the symbols in Formula (<NUM>) is the same as in the first embodiment, and as illustrated in <FIG> and <FIG>. According to this embodiment, the current distribution around the connecting members <NUM> is essentially the same regardless of the position of the connecting members <NUM>. In <FIG>, simulation results of the current density distributions of arrangements of the connecting members <NUM> satisfying Formula (<NUM>) are illustrated. The simulation conditions are the same as in the first embodiment. The illustrated positions are at the lower left of the heating resistance element <NUM>. The width of the frame region <NUM> is <NUM>, which is the same as in the first embodiment. The gap b of the connecting members <NUM> is <NUM> in <FIG>, <NUM> in <FIG>, and <NUM> in <FIG>. When the conditions of Formula (<NUM>) are satisfied, the direction in which the current flows for the connecting members <NUM> at the end portions as well as for the connecting members <NUM> in the center portion is essentially the same, and hence a phenomenon such as that seen in <FIG>, in which the current density at the four corners decreases, is less likely to occur. However, as the gap b of the connecting members <NUM> becomes wider and wider, a region in which the current distribution in the vicinity of the connecting members <NUM> is non-uniform widens. From around b=<NUM> (not shown), that non-uniform region starts to spread to the foaming region <NUM>. For this reason, it is desired that the gap b of the connecting members <NUM> be as small as possible. Specifically, it is desired that the gap b be <NUM> or less.

Ideally, Formula (<NUM>) and Formula (<NUM>) simultaneously hold for the width W of the heating resistance elements <NUM> in the Y direction.

Each of the symbols in Formula (<NUM>) is the same as in the first embodiment, and is as illustrated in <FIG> and <FIG>. As in the first embodiment, the terms amin and bmin represent the minimum dimension for the layout. When Formula (<NUM>) and Formula (<NUM>) are simultaneously satisfied, this means that the relationship c=b/<NUM> is satisfied and that the connecting members <NUM> are arranged at the minimum possible dimension and with the minimum possible gap in terms of the manufacturing process.

In order to make the current distribution of the heating resistance elements <NUM> uniform with respect to the width of the center region <NUM> in the Y direction, which is determined based on the foaming properties of the heating resistance elements <NUM>, it is desired that the width a or the gap b of the connecting members <NUM> be, while satisfying Formula (<NUM>) as far as possible, close to amin or bmin. When the width a of the connecting members <NUM> is widened, the region having a high current density widens. When the gap b of the connecting members <NUM> is widened, the region having a low current density widens. Therefore, when reducing the size of the region having a high current density, it is desired that the gap b of the connecting members <NUM> be widened, and when reducing the size of the region having a low current density, it is desired that the width a of the connecting members <NUM> be widened. The width a and the gap b of the connecting members <NUM> may both be widened. However, in all of the cases, in order to make the current distribution as uniform as possible, it is desired that the increase in amin or bmin be equally allocated among all of the connecting members <NUM>. Similar to the first embodiment, it is desired that the gap b of the connecting members <NUM> be <NUM> or less.

When it is difficult to equally allocate the increase in amin or bmin among all of the connecting members <NUM>, it is acceptable for the width a or the gap b of the connecting members <NUM> to be non-uniform. In this case, it is desired that b in Formula (<NUM>) be an average value of the gap b of the connecting members <NUM> based on one line. When Formula (<NUM>) cannot be satisfied, it is preferred that the overlap width c of both end portions be <NUM>/<NUM> or more to less than one times the average gap of n-number of connecting members <NUM> in the second direction Y. In particular, in order to increase the current density at the four corners of the heating resistance elements <NUM>, it is desired that the overlap width c of both end portions be <NUM>/<NUM> or more to less than <NUM>/<NUM> the average gap.

The second embodiment is particularly effective when the overlap width c can be set to a small value. However, when the overlap width c is large, as illustrated in <FIG>, the region in which current density is non-uniform may spread as far as the foaming region <NUM>. In a third embodiment of the present invention, not only a decrease in the current density at the four corners of the heating resistance elements <NUM> can be suppressed, but variation in the current distribution is less likely to occur, which may occur due to variation of the overlap width c and unevenness in the manufacturing positions of the connecting members <NUM>.

<FIG> is a plan view near the heating resistance element <NUM> according to the third embodiment. Similar to the first embodiment, the heating resistance element <NUM> is divided in the first direction X into the two electrode regions <NUM> each including the connecting region <NUM>, and the center region <NUM> positioned between the two electrode regions <NUM>. However, unlike the first embodiment, the two electrode regions <NUM> are longer than the center region <NUM> in the second direction Y. The width of the electrode regions <NUM> in the Y direction may be set independently of the width of the center region <NUM> in the Y direction. As a result, the connecting members <NUM> may be arranged in the electrode regions <NUM> without being subject to the width restriction of the center region <NUM> in the Y direction, which allows connecting regions <NUM> that is large in the Y direction to be obtained. According to this embodiment, the current density at the four corners of the heating resistance elements <NUM> can be increased. Even if deviation occurs in the manufacturing positions of the connecting members <NUM>, the current density at the four corners does not decrease. Further, in this embodiment, more connecting members <NUM> can be arranged than in the first embodiment or in the second embodiment. As a result, the number of connecting members <NUM> (resistors) connected in parallel to each other is increased, and a voltage loss of the connecting members <NUM> is decreased, leading to reduced power consumption.

In this embodiment as well, the plurality of connecting members <NUM> are positioned so that there is a gap between adjacent connecting members <NUM> in the second direction Y. In each electrode region <NUM>, the width a of each of the connecting members <NUM> is essentially the same, each gap b is essentially the same (the connecting members <NUM> are arranged at equidistant intervals), and each overlap width c of both sides in the Y direction is essentially the same. Further, the width a and the gap b of the connecting members <NUM>, and the overlap width c are essentially the same for the two electrode regions <NUM> as well. More specifically, in the two electrode regions <NUM>, the connecting members <NUM> are arranged in a symmetrical shape in the Y direction. The total of the widths of n-number of connecting members <NUM> in the Y direction is <NUM>% or less of the width of the electrode regions <NUM> in the Y direction. Similar to the first embodiment, it is desired that the gap b of the connecting members <NUM> be <NUM> or less. The connecting regions <NUM> are arranged within a range of the center region <NUM> in the second direction Y. Specifically, the two connecting members <NUM> positioned at the end portions in the Y direction (hereinafter referred to as end portion connecting members 102a and 102b) are arranged further inward than peripheral portions of the center region <NUM>. In the other embodiments, a part of the connecting regions <NUM> may be arranged outside of the range of the center region <NUM> in the second direction Y. In the following description, a distance between the side of the end portion connecting members 102a and 102b on the external side and the peripheral portions of the center region <NUM> (distance that the side of the end portion connecting members 102a and 102b on the external side is pulled in from the peripheral portions of the center region <NUM>) is referred to as a lead distance d.

In <FIG>, a simulation result of the current distribution according to this embodiment is illustrated. The simulation conditions are the same as in the first embodiment and the second embodiment. The width a of the connecting members <NUM> is <NUM>, the gap b of the connecting members <NUM> is <NUM>, the overlap width c is <NUM>, and the lead distance d is <NUM>. The width of the electrode regions <NUM> in the Y direction is larger than in the first embodiment, and hence <NUM> connecting members <NUM> are arranged, which is one more than in the first embodiment. The width of the frame region <NUM> is <NUM>, which is the same as in the first embodiment and the second embodiment. As illustrated in <FIG>, the width of the electrode regions <NUM> in the Y direction is wide, and hence a decrease in the current density at the four corners is suppressed.

In <FIG>, the current densities at various positions of the connecting members <NUM> are illustrated. <FIG> is an enlarged diagram of a lower left portion of the heating resistance element <NUM> illustrated in <FIG>. In <FIG>, the positions of the end portion connecting members 102a and 102b are shifted toward the inner side of the heating resistance element <NUM> from the positions illustrated in <FIG>. In the first embodiment, when the positions of the end portion connecting members 102a and 102b are shifted toward the inner side, the region in which the current is non-uniform widens, but in this embodiment, as illustrated in <FIG>, the region in which the current is non-uniform decreases in size. However, when the end portion connecting members 102a and 102b are shifted by a large amount toward the inner side, the region in which the current is non-uniform widens. Therefore, the lead distance d is preferably <NUM> or less, more preferably <NUM> or less. <FIG> is a diagram in which the contour range of the simulation result in <FIG> is widened. As can be seen from <FIG>, current is flowing through the end portion connecting member 102a side. Because the width of the electrode regions <NUM> in the Y direction is wide, the current flowing from the end portions of the connecting regions <NUM> to the outside in the Y direction increases, which results in a different current distribution from the first embodiment. Even in this embodiment, the current distribution may be made uniform by widening the connecting regions <NUM> in the Y direction. However, the region in which the current distribution is non-uniform can be minimized by arranging the connecting members <NUM> only on the side further inward than the width of the center region <NUM> in the Y direction. In addition, it is desired that the overlap width c on both sides in the Y direction be larger than the gap b of the connecting members <NUM>, and more commonly, it is desired that the overlap width c on both sides in the Y direction be larger than the average gap of the connecting members <NUM> in the second direction Y.

<FIG> is a plan view near the heating resistance element <NUM> according to a fourth embodiment of the present invention. The two electrode regions <NUM> and the center region <NUM> have the same dimension in the second direction Y, and the heating resistance element <NUM> has a rectangular flat shape. The connecting members <NUM> are arranged continuously in the second direction Y. In other words, the connecting regions <NUM> are completely filled with the connecting members <NUM>. The connecting members <NUM> are formed having a slit-like rectangular shape, which allows the current density in the heating resistance element <NUM> to be more uniform than in the first embodiment to the third embodiment.

In <FIG>, a simulation result according to this embodiment is illustrated. In the first embodiment to the third embodiment, the resistance of the connecting members <NUM> is large because the connecting members <NUM> are divided in the Y direction. For example, in the simulation result illustrated in <FIG>, a voltage loss of about <NUM>% occurs for an ideal quadrilateral-shaped heating resistance element <NUM> (in which current flows uniformly through the entire width of the heating resistance element <NUM>). In contrast, in the simulation result illustrated in <FIG>, the voltage loss is <NUM>% or less, which means that energy can be applied to the heating resistance element <NUM> with hardly any voltage loss. Thus, in this embodiment, except for the end portions of the connecting members <NUM>, the current distribution is uniform, and an ideal configuration of the heating resistance element <NUM> can be obtained.

In <FIG>, simulation results when the end portion positions of the connecting members <NUM> have been shifted are illustrated. In <FIG>, the lower left portion of the heating resistance element <NUM> illustrated in <FIG> is enlarged. In <FIG>, the end portion positions of the connecting members <NUM> illustrated in <FIG> have been shifted in the Y direction (the width of the connecting members <NUM> in the Y direction has changed). In <FIG>, the overlap width c is <NUM>, and in <FIG>, the overlap width c is <NUM>. In the case of a rectangular heating resistance element <NUM>, as the overlap width c becomes smaller and smaller, the region in which the current is non-uniform becomes less and less, and the current distribution is more ideal.

<FIG> is a plan view near the heating resistance element <NUM> according to a fifth embodiment of the present invention. The two electrode regions <NUM> and the center region <NUM> have different dimensions in the second direction Y, and the shape of the heating resistance element <NUM> is the same as in the third embodiment. The connecting members <NUM> are arranged continuously in the second direction Y. The shape of the connecting members <NUM> is the same as in the fourth embodiment. Therefore, similar to the fourth embodiment, the voltage loss of the connecting members <NUM> is very small. In this embodiment as well, forming the connecting members <NUM> in a slit-like rectangular shape allows the current density of the heating resistance element <NUM> to be more uniform than in the first embodiment to the third embodiment. In <FIG>, a simulation result according to this embodiment is illustrated. Similar to the fourth embodiment, the voltage loss is <NUM>% or less, which means that energy can be applied to the heating resistance element <NUM> with hardly any voltage loss. In this embodiment as well, except for the end portions of the connecting members <NUM>, the current distribution is uniform, and an ideal configuration of the heating resistance element <NUM> can be obtained.

In <FIG>, simulation results when the end portion positions of the connecting members <NUM> have been shifted are illustrated. In <FIG>, the lower left portion of the heating resistance element <NUM> illustrated in <FIG> is enlarged. In <FIG>, the end portion positions of the connecting members <NUM> illustrated in <FIG> have been shifted in the Y direction (the width of the connecting members <NUM> in the Y direction has changed). In <FIG>, the overlap width c is <NUM> and the lead distance d is <NUM>. In <FIG>, the overlap width c is <NUM> and the lead distance d is <NUM>. In <FIG>, the overlap width c is <NUM> and the lead distance d is <NUM>. From <FIG>, it can be seen that in the case of the heating resistance element <NUM> in which the electrode regions <NUM> are wider than the center region <NUM>, when the overlap width c is reduced, the region in which the current is non-uniform conversely increases in size. Similar to the principles discussed in the third embodiment, this is due to the current coming around from the end portions of the connecting members <NUM>. In the case of the shape of the heating resistance element according to this embodiment, it is preferred to set the overlap width c and the lead distance d to have a certain dimension in order to obtain a uniform current density distribution. The region in which the current is non-uniform is minimized when c in <FIG> is <NUM> and d in <FIG> is <NUM>. It is preferred that the lead distance d be <NUM> or less.

Various simulation results are shown in the above-mentioned embodiments. However, the relative positions of the actual heating resistance elements <NUM> and the connecting members <NUM> may be different from the simulation results depending on manufacturing accuracy and unevenness. The optimum values or the preferred values of the width a and the gap b of the connecting members <NUM>, the overlap width c, and the lead distance d shown in the simulation results may vary in a range of about ±<NUM>. For example, in the above-mentioned fifth embodiment, the optimum range of the overlap width c that minimizes the region in which the current is non-uniform is from <NUM> or more to <NUM> or less, and the optimum range of the lead distance d is from <NUM> or more to <NUM> or less.

In <FIG>, a configuration of an element substrate <NUM> according to a sixth embodiment of the present invention is illustrated. <FIG> is a plan view of the surface of the element substrate <NUM> in which the ejection orifices <NUM> are formed. <FIG> is an enlarged view of the portion A illustrated in <FIG>. The outer periphery of the element substrate <NUM> according to this embodiment is shaped roughly like a parallelogram. In the ejection orifice forming member <NUM> of the element substrate <NUM>, four lines of ejection orifices corresponding to cyan, magenta, yellow, and black (CMYK), respectively, are formed in two dimensions. Note that, in the following description, the direction that the ejection orifice lines in which the plurality of ejection orifices <NUM> are arranged extend is referred to as an "ejection orifice line direction".

As illustrated in <FIG>, recording elements <NUM>, which are heating resistance elements for causing a liquid to be foamed by heat energy, are arranged at positions corresponding to the ejection orifices <NUM>, respectively. The pressure chambers <NUM>, which include the recording elements <NUM>, are partitioned by a partition <NUM>. The recording elements <NUM> are electrically connected to the electrode pads <NUM> illustrated in <FIG> by electrical wirings 103c and 103d (refer to <FIG>) arranged in the element substrate <NUM>. The recording elements <NUM> are configured to cause the liquid to boil by generating heat based on a pulse signal input from a control circuit of a recording device (not shown). The liquid is ejected from the ejection orifices <NUM> by the force of the air bubbles produced by this boiling. As illustrated in <FIG>, in the ejection orifice line direction, a liquid supply channel <NUM> is extended on one side of each ejection orifice line, and a liquid recovery channel <NUM> is extended on another side. The liquid supply channel <NUM> and the liquid recovery channel <NUM> are flow channels that are arranged on the base material <NUM> of the element substrate <NUM> and are configured to extend in the ejection orifice line direction. The liquid supply channel <NUM> and the liquid recovery channel <NUM> are both in communication with the ejection orifices <NUM> via a supply port 300a and a recovery port 300b, respectively. The supply port 300a and the recovery port 300b are through holes passing through the substrate <NUM> of the element substrate <NUM> (refer to <FIG>). Based on this channel configuration, the liquid flowing through the liquid supply channel <NUM> is supplied to the recording elements <NUM> via a plurality of supply ports 300a, and ejected from the ejection orifices <NUM>. Of the liquid supplied to the recording elements <NUM>, liquid that has not been ejected is recovered in the liquid recovery channel <NUM> via a plurality of recovery ports 300b. The liquid recovered in the liquid recovery channel <NUM> is again supplied to the liquid ejection head via a tank portion arranged in the recording device. The liquid travels this flow route to be circulated. However, the present invention is not limited to the circulation configuration described in this embodiment. For example, the liquid may be supplied to the recording elements <NUM> from the liquid recovery channel <NUM> via the recovery ports 300b. Such a configuration is preferred, as this configuration allows the liquid to be supplied to the recording elements <NUM> from openings (300a and 300b) formed on both sides of the recording elements <NUM>, enables ejection symmetry to be obtained, and also allows refilling after ejection of the liquid to be performed comparatively quickly.

In an element substrate <NUM> such as that in this embodiment, which includes a plurality of ejection orifice lines (lines of the recording elements <NUM>) and a plurality of liquid openings (e.g., supply port 300a and recovery port 300b), which pass through the substrate <NUM>, the multi-layer wiring configuration illustrated in <FIG> is especially preferred. In such a configuration in which the recording elements <NUM> are two-dimensionally arranged, an element substrate <NUM> that suppresses an increase in the size of the substrate can be obtained by using the multi-layer wiring of the electrical wirings 103a and 103b and through hole configuration.

Further, arranging a plurality of the element substrates <NUM> enables a line-type liquid ejection head having a length corresponding to the width of the recording medium to be provided. In particular, by forming the outer periphery of the element substrates <NUM> roughly like a parallelogram, and arranging the plurality of element substrates <NUM> in a straight line (in-line) as in this embodiment, a compact line-type liquid ejection head that has a suppressed length in the short direction can be provided.

The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and functions.

Claim 1:
An element substrate (<NUM>) of a liquid ejection head, comprising:
a base material (<NUM>);
an insulating film (<NUM>) positioned on the base material;
a heating resistance element (<NUM>) configured to generate heat energy for ejecting a liquid;
a protective film (<NUM>) configured to cover the heating resistance element;
a first electrical wiring layer (<NUM>), which is arranged in the insulating film, and is configured to supply a current to the heating resistance element;
a second electrical wiring layer (<NUM>), which is arranged on a layer different from the first electrical wiring layer in the insulating film, and is configured to supply a current to the heating resistance element; and
a plurality of connecting members (<NUM>) configured to extend into the insulating film to connect the first electrical wiring layer and the heating resistance element, wherein
the heating resistance element being configured to cause the current to flow in a first direction (X),
the heating resistance element comprising a connecting region (<NUM>) to which the plurality of connecting members is connected,
the connecting region extending in a second direction (Y) intersecting the first direction, and
the heating resistance element is divided into, in the first direction, two electrode regions (<NUM>) each including the connecting region, and a center region (<NUM>) positioned between the two electrode regions,
characterized in that
the arrangement of the plurality of connecting members is determined based on the formulae <MAT>
when a width a [µm] represents a width of the connecting members in the second direction, a gap b [µm] represents a gap in the second direction between adjacent connecting members, an overlap width c [µm] represents a distance between the connecting members at both the ends and peripheral portions (101a, 101b) of the heating resistance element, amin, bmin, and cmin represent the minimum dimension for the layout, n represents a maximum number of the plurality of connecting members, and W [µm] represents a width of the heating resistance elements in the second direction.