JP4315018B2 - Liquid discharge head and liquid discharge apparatus - Google Patents

Description

  The present invention relates to a thermal liquid discharge head used in an ink jet printer and the like, and a liquid discharge device such as an ink jet printer including the liquid discharge head. The present invention relates to a technology that realizes a flow path structure without discharge unevenness.

Conventionally, for example, in a liquid discharge head used in a liquid discharge apparatus typified by an ink jet printer, a thermal method that uses expansion and contraction of generated bubbles, and a piezo method that uses fluctuations in the shape and volume of a liquid chamber, It has been known.
In the thermal method, a heating element is provided on a semiconductor substrate, bubbles are generated in the liquid in the liquid chamber by the heating element, and the liquid is ejected as droplets from a nozzle disposed on the heating element to be used as a recording medium. It ’s what makes you land.

FIG. 18 is an external perspective view showing a conventional liquid discharge head 1 of this type (hereinafter simply referred to as the head 1). In FIG. 18, the nozzle sheet 17 is bonded onto the barrier layer 3, and the nozzle sheet 17 is illustrated in an exploded manner.
FIG. 19 is a cross-sectional view showing the flow path structure of the head 1 of FIG. In addition, as this kind of flow path structure of a liquid discharge apparatus, it is disclosed by patent document 1, for example.
JP 2003-136737 A

  18 and 19, a plurality of heating elements 12 are arranged on the semiconductor substrate 11. In addition, the barrier layer 3 and the nozzle sheet 17 are sequentially stacked on the semiconductor substrate 11. Here, the one in which the heat generating element 12 is formed on the semiconductor substrate 11 and the barrier layer 3 is formed thereon is referred to as a head chip 1a. And what the nozzle sheet | seat 17 was bonded together on the head chip | tip 1a is called the head 1. FIG.

  The nozzle sheet 17 has nozzles 18 arranged so that nozzles (holes for discharging droplets) 18 are positioned on the respective heat generating elements 12. In addition, the barrier layer 3 is provided on the semiconductor substrate 11 so as to be interposed between the heating element 12 and the nozzle 18 to form a liquid chamber 3 a between the heating element 12 and the nozzle 18. .

  As shown in FIG. 18, the barrier layer 3 is formed in a substantially comb-like shape so as to surround the three sides of each heat generating element 12 in a plan view, so that the liquid chamber in which only one side is opened is formed. 3a is formed. This opened portion forms an individual flow path 3 d and communicates with the common flow path 23.

  The heating elements 12 are arranged in the vicinity of one side of the semiconductor substrate 11. In FIG. 19, the dummy chip D is arranged on the left side of the semiconductor substrate 11 (head chip 1a), so that one side surface of the semiconductor substrate 11 (head chip 1a) and one side surface of the dummy chip D are arranged. The common flow path 23 is formed. In addition, as long as it is a member which can form the common flow path 23, not only the dummy chip D but any member may be used.

  Furthermore, as shown in FIG. 19, a flow path plate 22 is disposed on the surface of the semiconductor substrate 11 opposite to the surface on which the heating elements 12 are provided. As shown in FIG. 19, the flow path plate 22 is formed with an ink supply port 22a and a supply flow path 24 having a substantially concave cross section so as to communicate with the ink supply port 22a. The supply channel 24 and the common channel 23 communicate with each other.

  Thus, the ink is sent from the ink supply port 22a to the supply flow path 24 and the common flow path 23, and enters the liquid chamber 3a through the individual flow path 3d. When the heat generating element 12 is heated, bubbles are generated on the heat generating element 12 in the liquid chamber 3a, and a part of the liquid in the liquid chamber 3a is used as a droplet by the flying force when the bubbles are generated. 18 is discharged.

  18 and 19, the actual shape is ignored and the shape is exaggerated for easy understanding. For example, the thickness of the semiconductor substrate 11 is about 600 to 650 μm, and the thickness of the nozzle sheet 17 and the barrier layer 3 is about 10 to 20 μm.

In the conventional head 1 described above, firstly, there is a problem that dust and dust enter the flow path and the nozzle 18, resulting in defective ejection at the nozzle 18 and insufficient supply of liquid in the flow path.
Here, garbage and dust drift in the general space and move freely. Therefore, they fall into the liquid and exist as dust and dust in the liquid. However, since the liquid ejecting apparatus such as an ink jet printer has a structure in which liquid is ejected from the nozzle 18 in units of microns, there is a possibility that dust or dust may clog the nozzle 18.

For this reason, at present, in the manufacturing process, for example, parts are washed with a dust or a liquid with little dust in a working environment such as a dust-free chamber.
Furthermore, in terms of design, it is necessary to provide filters for removing dust and dust at a plurality of locations in the flow path of the liquid ejection device.
In particular, as the number of nozzles increases as in a line head, there is a higher probability that ejection failure of the nozzles 18 will occur, so there is a problem that stricter management is required and the cost increases.

Secondly, as a result of the temperature of the head 1 increasing, bubbles may be generated in the liquid, and there is a problem that the amount of discharge becomes insufficient due to the bubbles.
Examples of the locations where bubbles are generated include the common flow path 23 and the individual flow paths 3d described above, but they may cause discharge unevenness regardless of where they are generated.

FIG. 20 is a diagram illustrating a result of taking a picture of a state in which bubbles remain in the common flow path 23. In FIG. 20, the nozzle sheet 17 is formed from a transparent body so that the state of bubbles inside can be seen.
In FIG. 20, a filter is provided in the common flow path 23. This filter is provided in order to prevent dust and dust from entering the individual flow path 3 d, and has columnar columns arranged along the common flow path 23.

As shown in FIG. 20, in the area where bubbles remain in the common flow path 23 (area surrounded by a dotted line in FIG. 20), the amount of liquid supplied to the individual flow path 3d decreases. As a result, the discharge amount of the liquid is reduced and appears as discharge unevenness in which the density is reduced in a relatively wide range.
Note that the discharge state is affected when bubbles are present. The discharge itself is affected by the reaction generated by the pressure generated during discharge and the liquid near the liquid chamber 3a, the barrier layer 3, and the presence of bubbles. This is probably because

In addition, bubbles may enter the vicinity of the inlet of the individual flow path 3d or the individual flow path 3d. FIG. 21 is a diagram illustrating a result of taking a photograph of a state in which bubbles remain at the inlet of the individual flow path 3d. In FIG. 21, similarly to FIG. 20, the nozzle sheet 17 is formed from a transparent body.
In such a case, even if the bubbles are small, the influence is great because the bubbles are present in a narrow space. That is, the discharge amount is smaller than in the case of FIG. Further, since only the discharge amount from the nozzle 18 corresponding to the individual flow path 3d into which bubbles have entered decreases, it becomes noticeable as a streak.

  Once the bubbles as described above are generated, even if the discharge is repeated, the bubbles stick to the common flow path 23 and the individual flow paths 3d or simply reciprocate between the individual flow paths 3d and the common flow path 23. Does not disappear. In addition, since the liquid is supplied into the liquid chamber 3a so as to pass through between the bubbles, a state where the ejection characteristics are insufficient often remains fixed.

In addition, since it is confirmed that the bubbles disappear when the discharge operation is stopped and the temperature of the liquid is lowered by standing for a long time, the bubbles in this case are formed by evaporation of the liquid. I understand that.
On the other hand, since the portion covered with bubbles is a gas, the thermal conductivity is poor, and the cooling by the liquid does not proceed, so the heat of the heat generating portion tends to accumulate. As a result, there is a problem that bubbles expand.

  Further, since bubbles tend to be generated particularly when the centers of the heating elements 12 and the nozzles 18 are shifted, the bubbles generated on the heating elements 12 remain without being effectively used for ejection. Conceivable.

Further, the bubbles may enter the liquid chamber 3a or the nozzle 18. FIG. 22 is a diagram showing a result of taking a picture of a state in which gas has entered the liquid chamber 3a from the nozzle 18.
In FIG. 22, a filter (in which triangular columns are arranged unlike FIG. 20) is provided in the common flow path 23, and the coalesced and grown bubbles block between the columns of the filter, and the liquid is liquid. This is a state where it cannot move to the chamber 3a side.

  When the movement of the liquid from the common flow path 23 to the liquid chamber 3a side is blocked by bubbles, the meniscus balance of the nozzle 18 is likely to be destroyed. In such a state, the shock wave from the adjacent nozzle 18 is triggered, and the gas enters the liquid chamber 3a from the nozzle 18. That is, since the pressure of the internal liquid is set to be lower than the atmospheric pressure, when the equilibrium state of the meniscus is destroyed, the liquid moves backward toward the common flow path 23 and cannot be discharged.

Thirdly, there is a problem that unevenness of discharge is caused by a shock wave at the time of discharge, particularly in combination with the presence of bubbles. In the thermal method, the pressure change during ejection is considerably larger than that in the piezo method.
There are the following two problems caused by the discharge impact.

  First, the shock wave triggers the drawing of bubbles from the adjacent liquid chamber 3a. In order to avoid this problem, it is conceivable to increase the distance between the filter columns. However, in such a case, dust and dust passing through the filter become large, and the individual flow path 3d. It becomes easy for large garbage and dust to enter.

  The second problem is that the shock wave propagates to the neighboring nozzles 18 and the meniscus vibrates to cause discharge unevenness. When bubbles are generated or residual bubbles are present, the shock wave and the bubbles are mixed with each other, the bubbles are likely to be drawn in, and ejection irregularities are likely to appear.

  By the way, in the case of a serial method in which dots can be superimposed to form an image (overwriting), even if there are about one to two nozzles that cause ejection unevenness, It is possible to repair the discharge unevenness so as not to be noticeable. On the other hand, in the case of a line method in which image formation is completed by one droplet ejection and, as a rule, overwriting cannot be performed, the presence of ejection unevenness is a fatal wound.

  The inventors of the present invention have already proposed a technology for reducing the influence of shock waves among the problems of ejection unevenness in Japanese Patent Application No. 2003-348709, which is an undisclosed prior application, and the bubble generation rate is as much as possible. A technique for reducing the size has already been proposed in Japanese Patent Application No. 2004-014183, which is also an undisclosed prior application.

  Further, the problem to be solved by the present invention is based on the above-described technology, and further improvements are made to make it difficult to cause a flow path failure due to dust, dust, etc., and to reduce the influence of bubbles as much as possible. It is to provide a flow path structure with almost no.

The present invention solves the above-described problems by the following means.
The invention according to claim 1, which is one of the present invention, is arranged on a semiconductor substrate at a constant pitch P in one direction, and adjacent ones in the direction perpendicular to the pitch P direction are X (X is 0). A plurality of heating elements arranged in a staggered manner so as to be shifted by a larger real number), a nozzle layer in which nozzles located on the heating elements are formed, and a barrier layer provided between the semiconductor substrate and the nozzle layer A liquid chamber formed by a part of the barrier layer and formed by a pair of walls facing each other so as to sandwich the heat generating element, and the pair of walls of the liquid chamber are approximately in the arrangement direction of the heat generating elements. A distance between the pair of walls in the liquid chamber is provided by a pair of individual flow paths that are formed by extending in a vertical direction and are arranged on both sides of the liquid chamber so as to communicate with the liquid chamber. U and said individual A channel width W of the road is formed so as to satisfy the relationship U> W, the pair of individual flow paths comprises: a first individual flow path connected to the common flow path, the first individual flow path On the other hand, it comprises a second individual flow path extending in the opposite direction across the liquid chamber, and a wall is formed along the arrangement direction of the heat generating elements at a predetermined distance from the tip of the second individual flow path. The second individual flow paths of all the liquid chambers are located between the wall formed at a predetermined distance from the tip of the second individual flow path and the tip of the second individual flow path. The filter is composed of a plurality of pillars in the common flow path, and the pillars of the filter are arranged at a pitch 2P in the arrangement direction of the heating elements, and are arranged in a staggered manner. Of the heating elements, the center of the heating element closer to the filter and the center of the column A liquid discharge head which is located on the same line in a direction perpendicular to the array direction of the heating elements.

(Function)
In the said invention, the two separate flow paths connected to a liquid chamber are provided. Further, the width of the liquid chamber is formed larger than the width of the individual flow path. Therefore, even if bubbles are generated in one individual flow path and the liquid cannot be supplied from the individual flow path to the liquid chamber, the liquid can be supplied from the other individual flow path. Even if two individual flow paths are provided, the pressure required to discharge the liquid can be maintained by making the flow path width of the individual flow path narrower than the width of the liquid chamber.
In addition, although the nozzle layer and the barrier layer are provided separately in the following embodiments (the barrier layer 13 and the nozzle sheet 17), both may be integrated.

  According to the present invention, even when bubbles or the like are clogged in one of the two individual flow paths, the liquid can be supplied from the other individual flow path into the liquid chamber, that is, the priming effect can be exhibited. In addition, since the influence of the shock wave can be reduced, fluctuations in meniscus can be suppressed and image quality can be improved.

  In addition, even if bubbles are generated, there is little probability that the liquid discharge head itself will be down, so the operating rate can be improved. Furthermore, since kogation hardly occurs, the head life can be extended.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The liquid ejection device according to the present invention is an ink jet printer (thermal color line printer; hereinafter simply referred to as a printer) in the embodiment, and the liquid ejection head is the line head 10 in the embodiment.

  FIG. 1 is an external perspective view showing a line head 10 of this embodiment. The line head 10 has four rows of head chips 19 in which head chips 19 are arranged in a line for the width of the A4 size photographic paper, arranged in four rows, and each row has Y (yellow), M (magenta), This is a four-color head of C (blue green) and K (black).

  The line head 10 is formed by arranging a plurality of head chips 19 side by side in a zigzag pattern and bonding the lower portions of these head chips 19 to a single nozzle sheet 17 (nozzle layer). Here, each nozzle 18 formed on the nozzle sheet 17 is located at a position corresponding to each heating element 12 (described later) of all the head chips 19 (specifically, the center axis of the heating element 12 and the center of the nozzle 18). Arranged so that the axis line coincides). In the present embodiment, each heating element 12 is composed of one heating element. However, the present invention is not limited to this. Each heating element 12 may be configured in a plurality of divided configurations such as a configuration divided into two.

The head frame 16 is a support member that supports the nozzle sheet 17 and has a size corresponding to the nozzle sheet 17. Moreover, the length of each accommodation space 16a is matched with the lateral width (about 21 cm) of A4 size.
The four head chip 19 rows are arranged inside the housing space 16 a of the head frame 16 for each row. In addition, an ink tank that stores inks of different colors is attached to the storage space 16a of the head frame 16 on the back surface of the head chip 19, so that each storage space 16a, that is, each head chip 19 is mounted. Different colors of ink are supplied to the columns.

FIG. 2 is a plan view showing one head chip 19 row. In FIG. 2, the head chip 19 and the nozzle 18 are shown in an overlapping manner.
Each head chip 19 is arranged in a staggered manner, that is, adjacent head chips 19 are 180 degrees different from each other. As shown in FIG. 2, between the head chips 19 arranged at the “N−1” th and “N + 1” th and the head chips 19 arranged at the “N” th and “N + 2” th, A common flow path 23 for supplying ink to the head chip 19 is formed.
Further, as shown in FIG. 2, the intervals between the nozzles 18 are all equal, including the staggered adjacent portions.

  The above-described line head 10 is fixed in the printer main body, and the surface (ink landing surface) of the recording medium (printing paper) is the ink discharge surface (nozzle sheet) of the line head 10 with respect to the fixed line head 10. 17) and the recording medium is moved relative to the line head 10 while maintaining a predetermined gap. During this relative movement, ink is ejected from the nozzles 18 of the head chip 19 so that dots are arranged on the recording medium, whereby characters, images, and the like are printed in color.

  Next, the head chip 19 of this embodiment will be described in more detail. The head chip 19 is the same in that the heating elements 12 are arranged on the semiconductor substrate 11 as compared with the conventional head chip 1a. However, the shape of the barrier layer 13 provided on the semiconductor substrate 11 is different. The shape of the barrier layer 13 is different because the shapes of the liquid chamber 13a and the individual flow paths 13d and 13e are different.

FIG. 3 is a plan view showing the shape of the barrier layer 13 of the head chip 19 of the present embodiment.
As in the prior art, the heating elements 12 are arranged on the semiconductor substrate. A pair of walls 13 b are formed on both sides of each heating element 12 by a part of the barrier layer 13. That is, a pair of walls 13b are provided on both sides in the arrangement direction of the heating elements 12 (left and right direction in FIG. 3), and the heating elements 12 are disposed between the pair of walls 13b. A chamber 13a, a first individual channel 13d, and a second individual channel 13e are formed.

  In this embodiment, the liquid chamber 13a includes the region of the heat generating element 12, and among the rectangular region slightly larger (one turn) than the region of the heat generating element 12, the liquid chamber 13a is an octagonal region chamfered at four corners. It has an octagonal column area as the base. Of course, the octagonal column region of the liquid chamber 13a is not limited to this.

  Further, an individual flow path communicating with the liquid chamber 13a is formed by the pair of walls 13b. In this embodiment, the extending direction of the individual flow path is a direction (vertical direction in the drawing) perpendicular to the arrangement direction of the heat generating elements 12 (horizontal direction in the drawing). The term “vertical” means substantial vertical, and includes not only those that are physically completely vertical, but also those that are close to vertical but not completely vertical (substantially vertical) (hereinafter the same).

  The individual flow path includes a first individual flow path 13d that is connected to the common flow path 23, and a second individual flow path 13e that extends to the opposite side of the first individual flow path 13d across the liquid chamber 13a. Here, the first individual flow path 13d corresponds to the individual flow path 3d shown in the prior art (FIG. 18).

  With the above structure, all the liquid chambers 13a are connected to the first individual flow path 13d and the second individual flow path 13e. In addition, all the first individual flow paths 13 d are connected to the common flow path 23. Further, all the second individual flow paths 13e communicate with each other.

FIG. 4 is a plan view showing the relationship between the width U of the liquid chamber 13a and the channel width W of the first individual channel 13d and the second individual channel 13e.
As shown in FIG. 4, the distance between a pair of walls 13b provided on both sides of the liquid chamber 13a is defined as the width U of the liquid chamber 13a, and the flow of the first individual flow path 13d and the second individual flow path 13e. The road width is defined as W. Note that the width of the liquid chamber 13a is U in almost the entire range of the liquid chamber 13a and at least in the region on the heating element 12. Therefore, the width in a part of the liquid chamber 13a is narrower than U. Also, the first individual flow path 13d and the second individual flow path 13e also have a flow path width W over almost the entire range.

In this case, in the present embodiment, the width U of the liquid chamber 13a and the channel width W of the first individual channel 13d and the second individual channel 13e are:
U> W
It is formed to satisfy the relationship.

The reason for forming in this way is as follows.
Since the region on the heating element 12 is a region where the liquid is heated and boiled, the wall 13b of the barrier layer 13 is not covered with this region (at least the barrier layer 13 does not exist in the region on the heating element 12). To be formed). The wall 13b is necessary to direct the pressure toward the nozzle 18 when the heating element 12 generates heat and the liquid in the region on the heating element 12 boils down.

At this time, in the structure of the present embodiment, since there are the first individual flow path 13d and the second individual flow path 13e in two directions, the pressure is dispersed in these directions.
Therefore, in order to increase the pressure, it is conceivable to narrow the width U and the flow path width W of the liquid chamber 13a. Here, the width U of the liquid chamber 13a cannot be narrowed to be less than the region of the heat generating element 12, but the flow path width W can be narrowed within a range where there is no problem. For this reason, in this embodiment, the relationship between the width U of the liquid chamber 13a and the flow path width W is U> W.

FIG. 5 is a plan view showing the relationship among the width U of the liquid chamber 13a, the flow path width W1 of the first individual flow path 13d, and the flow path width W2 of the second individual flow path 13e.
In the example of FIG. 4 above, when W1 = W2 = W,
U> W.
In contrast,
W1 ≠ W2
It may be. In this case, the relationship between the width U of the liquid chamber 13a, the channel width W1 of the first individual channel 13d, and the channel width W2 of the second individual channel 13e is
U> W2 ≧ W1
If it is good.

FIG. 6 is a plan view showing the relationship between the channel length of the second individual channel 13e and the arrangement pitch P of the liquid chambers 13a (the heating element 12 or the nozzle 18 is the same).
In FIG. 6, a wall (barrier layer) that is farthest from the liquid chamber 13 a in a portion where the line connecting the centers of the liquid chambers 13 a in the arrangement pitch P direction and the second individual flow paths 13 e between the adjacent liquid chambers 13 a communicate with each other. Let L be the distance to the line in contact with 13).
At this time,
L ≦ 2 × P
It is formed to satisfy the relationship.

The reason for forming in this way is as follows.
When a stress (shear stress) in the direction in which the nozzles 18 are arranged is applied to the nozzle sheet 17 due to thermal distortion during a temperature rise or the like, a force that deforms the barrier layer 13 is applied. In this case, if the adhesion area between the nozzle sheet 17 and the barrier layer 13 is large, the barrier layer 13 hardly deforms. However, as in the present embodiment, the elongated individual channels (the first individual channel 13d and the first individual channel 13 When the two individual flow paths 13e) are provided, the wall 13b of the barrier layer 13 is likely to be deformed (because the total length of the individual flow paths is about twice that of the conventional individual flow path 3d). .

  That is, it is resistant to shear stress along the flow direction of the individual flow paths (direction perpendicular to the arrangement direction of the liquid chambers 13a), but is perpendicular to the flow direction of the individual flow paths (alignment direction of the liquid chambers 13a). It becomes weak to the shear stress. Thereby, the nozzle 18 of the nozzle sheet 17 and the heating element 12 are relatively easily displaced.

  In such a case, in order to minimize the above deformation, the length of L in FIG. 6 needs to be within a certain range. Therefore, the above deformation is minimized by providing the relationship between L and P as described above.

  Although the liquid chambers 13a are arranged at a constant arrangement pitch P in one direction, the liquid chambers 13a are not arranged in a line (on a straight line), and the adjacent liquid chambers 13a (the heating element 12 or the nozzle 18 is also the same). May be arranged at a predetermined interval X (X is a real number larger than 0) in a direction perpendicular to the arrangement pitch P direction. This technique has already been proposed by the present applicant (Japanese Patent Application No. 2003-383232).

As a result, the center-to-center distance between the adjacent nozzles 18 is larger than the arrangement pitch P of the liquid chambers 13a, so that the deformation amount of the nozzles 18 and their surrounding areas due to pressure fluctuations accompanying the discharge of liquid droplets is reduced. It is possible to stabilize the droplet discharge amount and the discharge direction.
In this case, among the plurality of liquid chambers 13a, a line connecting the centers of the liquid chambers 13a arranged on the side away from the common flow path 23 (that is, a line connecting the centers of every other liquid chamber 13a). And the distance between the line (barrier layer 13) that is farthest from the liquid chamber 13a in the portion where the second individual flow paths 13e between the adjacent liquid chambers 13a communicate with each other is L, The above relationship (L ≦ 2 × P) is satisfied.

Next, the structure on the common flow path 23 side will be described.
In FIG. 3 and the like, nothing is shown in the common flow path 23. However, it is preferable to provide a filter 24 or the like in the common flow path 23 as shown in FIG. The filter 24 is formed by the barrier layer 13 (the same applies to a filter 25 described later).

FIG. 7 is a plan view showing a state in which the filter 24 is provided in the common flow path 23. The filter 24 has columns 24a arranged in the arrangement direction of the liquid chambers 13a. In the example of FIG. 7, the column 24a is formed from a substantially rectangular column. Furthermore, in the example of FIG. 7, the lateral width (length in the longitudinal direction) of the pillar 24a is formed to be substantially equal to the length between the outer wall surfaces of the pair of walls 13b (flow path width W + thickness of the wall 13b × 2). ing.
By the way, if the heating element 12 of FIG. 7 is a staggered arrangement proposed in the above-mentioned Japanese Patent Application No. 2003-383232 as shown in FIG. 8, the following effects are obtained.
When the heating elements 12 are arranged in a staggered arrangement as shown in FIG. 8, there are a heating element 12 closer to the filter 24 and a heating element 12 farther away. The far heating element 12 is close to the wall and can increase the pressure during ejection, while the supply distance during refilling becomes long, and it takes time to complete the refilling operation. On the other hand, the heating element 12 closer to the filter 24 refills quickly but does not increase the discharge pressure. Therefore, when the filter 24 is arranged as shown in FIG. 8, since the column 24a of the filter 24 has the same effect as the wall, the discharge pressure increases, and the column 24a of the filter 24 also works to delay the refill operation. Thus, the difference in the discharge operation between the heater element 12 closer to and the heater element 12 farther away can be reduced.

By the way, the relationship between the gap Wf between the pillars 24a and the channel width W of the first individual channel 13d is:
W ≧ Wf
It is formed to satisfy.
The height of the gap Wf between the columns 24a is formed so as not to exceed the height of the first individual flow path 13d.

  The reason for this is to make it possible to remove dust and dust that may be clogged in the first individual flow path 13d with the filter 24 on the front side of the first individual flow path 13d. That is, dust or the like that has passed through the filter 24 is prevented from being clogged in the first individual flow path 13d.

  The liquid is supplied in the order of the common flow path 23 → the filter 24 → the first individual flow path 13d → the liquid chamber 13a, and at least the liquid that has passed through the filter 24 is filled in the second individual flow path 13e. Therefore, if the channel width (and height) of the second individual channel 13e is equal to or greater than the channel width W (and height) of the first individual channel 13d, the flow of the first individual channel 13d Even if it is not the same as the road width W (and height), dust or the like is not clogged.

  FIG. 9 is a plan view showing another embodiment of the filter (filter 25). The filter 25 of FIG. 9 is provided with substantially square columns 25a along the arrangement direction of the liquid chambers 13a. Further, the arrangement pitch of the columns 25a is arranged at the same pitch as the arrangement pitch P of the liquid chambers 13a (the same applies to the heating elements 12 or the nozzles 18). Furthermore, the center of the column 25a is located on the center line (channel center line) of the first individual channel 13d. This line is also the central line of the second individual flow path 13e.

Furthermore, as shown in FIG. 9, when the distance between the end of the first individual channel 13d on the column 25a side and the end of the column 25a on the first individual channel 13d side is Wb, the distance Wb And the channel width W of the first individual channel 13d,
Wb ≧ W
It is formed to satisfy.

This is because, when formed as described above, it has been confirmed by experiments that shock wave interference during liquid ejection is reduced. The shape of the pillar 25a is not limited to a substantially square shape, and may be any shape such as a rectangular shape as shown in FIG. 7, a triangular shape, a pentagonal or higher polygonal shape, a circular shape, an elliptical shape, or an oval shape. .
Further, even when the heating elements 12 are arranged in a staggered manner as shown in FIG. 8, by arranging the pillars 25a as shown in FIG. 9, the heating elements 12 closer to the pillars 25a and the farther ones as shown in FIG. It is possible to reduce the difference in the discharge operation with the heat generating element 12.

  Next, the relationship between the opening area of the nozzle 18, the flow path area of the first individual flow path 13d, and the cross-sectional area of the gap between the columns 24a of the filter 24 will be described. Note that the cross-sectional area of the gap between the pillars 24 a is not limited to the filter 24 but applies to all filters such as the filter 25.

  First, when comparing the cross-sectional area of the gap between the pillars 24a and the flow path area of the first individual flow path 13d, the cross-sectional area of the gap between the pillars 24a is included in the flow path area of the first individual flow path 13d. The size is formed. Furthermore, when the flow path area of the first individual flow path 13d and the opening area of the nozzle 18 are compared, the flow path area of the first individual flow path 13d is formed in a size that is included in the opening area of the nozzle 18. Has been.

  FIG. 10 is a diagram illustrating the above concept. Note that the area defined as described above is not limited to the shape of the opening of the nozzle 18 being circular (shown by a solid line in FIG. 10), but an ellipse (shown by a broken line in FIG. 10) or an ellipse (oval type). ) (Shown by a one-dot chain line in FIG. 10) and the like, and the cross-sectional area of the gap between the pillars 24a and the flow path surface area of the first individual flow path 13d are not limited to the rectangular shape, This is because the shape can be considered.

Also in this embodiment, the opening shape of the nozzle 18 can be selected from a circle, an ellipse, or an ellipse, and the cross-sectional shape of the gap between the first individual flow path 13d and the column 24a is, for example, a rectangular shape. be able to.
Here, the opening diameter of the discharge surface of the nozzle 18 in the arrangement direction of the nozzles 18 is Dx, and the opening diameter of the discharge surface of the nozzle 18 in the direction perpendicular to the opening diameter Dx (direction perpendicular to the arrangement direction of the nozzles 18) is Dy. When
Dx ≧ Dy
It is.
In this case, when the diagonal length of the rectangular channel surface of the first individual channel 13d is L1, and the diagonal length of the rectangular cross section of the gap between the columns 24a is L2,
Dx>L1> L2
It is formed to satisfy the relationship.

  If formed in this way, the dust and dust that first pass through the gaps between the pillars 24a of the filters 24 provided in the common flow path 23 (without clogging in the first individual flow path 13d, etc.) It can always pass through the individual flow path 13d. Furthermore, since there is a relationship of the above-described width U> the width of the liquid chamber 13a> the flow path width W, dust, dust, and the like that have passed through the first individual flow path 13d can reach the liquid chamber 13a. Furthermore, since the opening area of the nozzle 18 is the largest, dust, dust and the like in the liquid chamber 13a can pass through the nozzle 18, that is, be discharged to the outside together with the liquid when the liquid is discharged.

  FIG. 11 is a plan view showing another embodiment of the shape of the second individual flow path 13e. As shown in FIG. 3 and the like, in the above embodiment, on the barrier layer 13 side of the second individual channel 13e (the side farthest from the common channel 23), all the second individual channels 13e communicate with each other. Is formed.

  On the other hand, in FIG. 11, the wall 13b is formed so that two adjacent second individual flow paths 13e communicate with each other. The communication between the second individual flow paths 13e is not limited to two adjacent in this way, and may be three or more. This is because if at least two second individual flow paths 13e communicate with each other, the liquid flows from one second individual flow path 13e to the other second individual flow path 13e.

Moreover, even if it is a structure like FIG. 11, it is formed so that the various relations mentioned above may be satisfy | filled.
For example, the wall that is farthest from the liquid chamber 13a in the portion that connects the line connecting the centers of the liquid chambers 13a in the arrangement pitch P direction of the liquid chambers 13a and the second individual flow paths 13e between the adjacent liquid chambers 13a ( The relationship between the distance L between the lines in contact with the barrier layer 13) and the arrangement pitch P is similar to the above.
L ≦ 2 × P
It is formed to satisfy.

In addition, when communicating the 2nd 2nd separate flow path 13e, as shown in FIG. 11, other than the case where it makes a substantially U shape, a substantially concave shape etc. may be sufficient, for example.
Although not shown in FIG. 11, in the case of such a structure, a filter is provided in the common flow path 23 as in the above example.

  Subsequently, the reduction of the discharge impact pressure in the structure of the present embodiment will be described. FIG. 12 is a plan view for explaining the state of shock wave propagation during liquid ejection. In order to make the difference from the prior art easier to understand, the conventional structure (FIG. 18) is shown on the left side in the figure, and the structure of this embodiment is shown on the right side in the figure.

  In both cases, the common flow path 23 has a substantially triangular column shape (however, it is not limited to this shape and may be a columnar shape as described above) (FP1 to FP5 in the drawing). The filter 26 is arranged. And it arrange | positions so that the center of each pillar may respectively correspond to the center of the separate flow path 3d and the 1st separate flow path 13d.

  The columns are arranged in this way when a shock wave having a positive pressure (in the direction of pushing out the liquid from the nozzle 18) is generated in the first stage of liquid discharge, and the individual flow path 3d or the first individual flow path 13d is connected thereto. In the common flow path 23, only a portion close to the liquid chamber 3a or 13a receives a large impact, and the ripple to the other individual flow paths 3d, the liquid chamber 3a, the first individual flow path 13d, or the liquid chamber 13a is minimized. This is because the overall interference is reduced.

  In the conventional structure, when the liquid is discharged in the liquid chamber 3a-2, expansion due to generation of bubbles for discharging the liquid occurs at first, and a large positive pressure is generated to push the liquid out of the nozzle 18. The negative pressure is generated in the liquid chamber 3a-2 due to the bubble contraction immediately after discharge, and the suction force (P in the figure) in the direction of being drawn into the liquid chamber 3a-2 acts on the liquid existing in the individual flow path 3d. . In particular, in the conventional structure, the amount corresponding to the liquid lost (discharged) from one individual flow path 3d is taken in. However, since the liquid is continuous and mass and viscous resistance act, the liquid cannot immediately move. For this reason, a shock wave first propagates.

The shock wave attenuates as the distance increases, but propagates in the liquid and is transmitted to the outside of the filter 26 and to the adjacent liquid chambers 3a-1 and 3a-3.
When the shock wave is transmitted to one of the liquid chambers 3a, the meniscus of each nozzle 18 changes. When the vibration reaches the liquid chamber 3a (when the meniscus fluctuates), if discharge is performed from the liquid chamber 3a, it is considered that interference occurs and discharge unevenness occurs.

On the other hand, in the present embodiment, for example, when the liquid is discharged in the liquid chamber 13a-2, the shock wave propagates in both the left and right directions, that is, both the first individual flow path 13d and the second individual flow path 13e. , The energy is divided in two and propagates in each direction. That is, in the conventional structure, since only the individual flow path 3d side is opened, the energy directed to the opposite side of the individual flow path 3d is immediately reflected by the wall and synthesized into a component that is directed outward from the individual flow path 3d. . On the other hand, in the structure of the present embodiment, half of the energy is radiated in opposite directions.
In the present embodiment, since suction force is generated in both the first individual channel 13d and the second individual channel 13e, the magnitude of the suction force generated in each individual channel is P / 2. . Thereby, the influence of a shock wave can be halved.

  In the present embodiment, the filter 26 is provided at the outlet of the first individual channel 13d (in the common channel 23), and the wall 27 is provided at the outlet of the second individual channel 13e. By doing so, the shock wave converges in the smallest possible range.

  Next, the influence of bubbles in the structure of this embodiment will be described. FIG. 13 is a plan view for explaining a state when bubbles are generated. Also in FIG. 13, in order to make the difference from the prior art easier to understand, the conventional structure is shown on the left side in the figure, and the structure of this embodiment is shown on the right side in the figure.

  When a large number of liquid discharges per unit area or a high-density image or the like is continuously recorded, the head is overheated, and bubbles are likely to be generated at the portion where the liquid contacts. The generated bubbles merge to grow into a relatively large bubble. Under such circumstances, air bubbles may be pushed toward the filter 26 and stick (FIG. 13).

  When the grown bubbles are pressed against the filter 26, the liquid is not ejected so frequently in the vicinity, and when the amount of liquid movement is such that the refill is in time with the liquid supplied from a slightly separated location, the bubbles are In this case, it is in contact with the vicinity of the inlet of the filter 26 (the left corner of the column of the filter 26 in the figure). However, if the discharge frequency increases and the movement of the liquid is not in time, the liquid pressure (water pressure) in the vicinity decreases, and the bubbles adhering to the filter 26 by that amount are near the outlet of the filter 26 (right side in the figure). Sucked up. FIG. 13 illustrates the bubbles when such a state is reached.

  If such a state continues further, bubbles will be ejected from between the columns of the filter 26 and drawn into the individual flow path 3d or the first individual flow path 13d, or the meniscus of the nozzle 18 will be destroyed and shown in FIG. As described above, gas (bubbles) is drawn from the nozzle 18. It has been experimentally confirmed that the shock wave mentioned above is the trigger at this time.

  When air bubbles are drawn into the individual flow path 3d in the conventional structure (see FIG. 13), if the size of the air bubbles is small and does not cover the flow path surface (cross section) of the individual flow path 3d, the process is repeated. During the ejection to be performed, the nozzle 18 is discharged to the outside. On the other hand, when it is a bubble of the magnitude | size which block | closes the separate flow path 3d, it will be divided into the liquid chamber 3a side and the common flow path 23 side.

  If bubbles are present in the liquid chamber 3 a, the liquid cannot reach the nozzle 18. This is because the internal pressure is set lower than the atmospheric pressure. When energy is applied to the heat generating element 12 that is not covered with the liquid, the slightly remaining liquid immediately disappears, and thereafter, it is in an baked state. As a result, unless a special cleaning operation is performed, ejection defects such as failure to recover can easily occur. Furthermore, kogation is accelerated.

  Here, in the serial type head capable of overwriting, even if there are about one nozzle 18 with poor ejection, it can be repaired so as not to be noticeable by overwriting. On the other hand, in the line head system, if even one defective nozzle 18 exists, it is reflected in the image quality as it is.

  And as this concrete measure, it is restraining the discharge cycle below a certain level. Thereby, the emitted-heat amount can be decreased. In addition, since the discharge pitch can be slowed, the internal pressure can be prevented from decreasing until the bubbles enter the individual flow path 3d.

  In addition, in the right side of FIG. 13, in the structure of the present embodiment, a state is shown in which bubbles are drawn into the first individual flow path 13d. Since the nozzle 18 is dominated by the liquid in both the first individual flow path 13d and the second individual flow path 13e, even if air bubbles try to enter the liquid chamber 13a-2 from the first individual flow path 13d side, As long as there is no liquid ejection or bubble disappearance, the equilibrium in this state continues.

  When the discharge is continuously performed in this state, the shock wave is applied to both the first individual flow path 13d and the second individual flow path 13e, but in the liquid chamber 13a-2, the first individual flow path 13d side. Since the air bubbles are clogged, the air bubbles are attracted and eventually reach the liquid chamber 13a-2. And the wall of the liquid which exists between the nozzles 18 is destroyed, and the bubbles are discharged to the outside. At this time, bubbles are discharged by one or several discharges, but the liquid chamber 13a-2 in the meantime continues to function as a pump and replenishes liquid from the second individual flow path 13e side (that is, priming water) As a role).

  Therefore, in the structure of the present embodiment, even if one of the individual channels (in this example, the first individual channel 13d) is blocked with bubbles, the other individual channel (in this example, the second individual channel) As long as 13e) is filled with the liquid, the liquid continues to be supplied to the liquid chamber 13a, so that the bubbles are discharged to the outside and can return to a normal state. Therefore, it is possible to have a self-cleaning effect on the bubbles, the possibility that the heat generating element 12 is burned out can be made extremely low, and the possibility of causing a discharge failure can be almost eliminated.

  Since the liquid filled in the second individual flow path 13e is also the liquid that has passed through the filter 26, dust, dust, and the like are hardly clogged in the second individual flow path 13e. Further, on the second individual flow path 13e side, there is no part that becomes a resistance during the movement of the liquid, such as the filter 26, so even if there are some bubbles, it does not hinder the movement of the liquid. From these things, it is considered impossible that the liquid cannot be replenished into the liquid chamber 13a from the second individual flow path 13e.

Next, examples of the present invention will be described.
Example 1
FIG. 14 is a diagram showing a result (photographing result) of confirming a reduction in shock wave in the conventional structure and the structure of this example.
In the first embodiment, 600 DPI (nozzle interval is 42.3 μm) and 320 heating elements 12 arranged on the semiconductor substrate 11 were used (size is about 16 mm × 1.6 mm).

Also, a nozzle sheet 17 made of a transparent acrylic resin was used so that the internal behavior could be seen. The experimental results in FIG. 14 correspond to the diagram shown in FIG.
In FIG. 14, the conventional structure uses the nozzles 18 arranged in a straight line. However, in the embodiment, the nozzles 18 arranged in a staggered manner are used (this difference). It is considered that there is no difference in the impact of the shock wave.

  In FIG. 14, the nozzle 18 immediately after the liquid is discharged appears to be black due to a drastic fluctuation in the liquid level due to the influence of the shock wave. In the conventional structure, the vertical line of the heating element 12 on the lower side is hardly visible (note that the heating element 12 has a vertically divided shape), but in the structure of the example, Is relatively visible. Further, in the conventional structure, the adjacent nozzle 18 also appears black due to the influence of the shock wave, but it can be seen that the degree is small in the structure of the embodiment.

(Example 2)
FIG. 15 is a plan view showing a specific structure of the head used in the second embodiment. In Example 2, as shown in FIG. 15, a liquid storage region 28 in which columns 28 a are arranged is provided between the outlet of the second individual flow path 13 e and the wall of the barrier layer 13. The filter 25 provided in the common flow path 23 is the same as the filter 25 shown in FIG.

FIG. 16 is a diagram showing a result of sequentially taking pictures of how bubbles are discharged using the head having the structure of FIG. FIG. 16 shows a state in which bubbles are discharged in the order of “1” → “2” →... → “9”.
In FIG. 16, at “1”, bubbles are injected from the nozzle 18 and are clogged between the storage region 28 and the second individual flow path 13e. Then, as illustrated in “1”, when the liquid discharge operation was repeated using the third nozzle 18 from the left side, bubbles were gradually discharged from the nozzle 18.

(Example 3)
FIG. 17 is a diagram showing a part of a mask diagram of a prototype of a head (with a nozzle pitch of 42.3 μm and a resolution of 600 DPI). In FIG. 17, the upper side is the common flow path 23 side. In FIG. 17, the left side is an embodiment corresponding to FIG. 11, and the right side is an embodiment corresponding to FIG.

That is, in FIG. 17, the left side is a communication between the adjacent second individual flow paths 13e. Moreover, the right side in FIG. 17 is the one in which all the second individual flow paths 13e are communicated.
Furthermore, the filter is formed of a substantially triangular prism. Furthermore, the heating elements are arranged in a staggered pattern.

  When we actually tried printing with the above-mentioned heads, in all of the conventional structures, burst errors (wide color unevenness, white spots in single colors are likely to appear as the temperature increases during continuous printing or at the first printing at low temperatures). Almost disappeared). Since the semiconductor substrate 11 and the heating element 12 are the same as the conventional ones and only the flow channel structure is different, the effect of the flow channel structure of the present invention was confirmed.

It is an external appearance perspective view which shows the line head of this embodiment. It is a top view which shows one head chip row | line | column. It is a top view which shows the shape of the barrier layer of the head chip of this embodiment. It is a top view which shows the relationship between the width | variety U of a liquid chamber, and the flow path width W of a 1st separate flow path and a 2nd separate flow path. It is a top view which shows the relationship between the width U of a liquid chamber, the flow path width W1 of a 1st separate flow path, and the flow path width W2 of a 2nd separate flow path. It is a top view which shows the relationship between the flow path length of a 2nd separate flow path, and the arrangement pitch P of a liquid chamber. It is a top view which shows the state which provided the filter in the common flow path. FIG. 8 is a plan view showing a staggered arrangement of the heating elements of FIG. 7. It is a top view which shows other embodiment of a filter. It is a figure explaining the relationship with the opening area | region of a nozzle, the flow-path surface area | region of a 1st separate flow path, and the cross-sectional area | region of the clearance gap between the pillars of a filter. It is a top view which shows other embodiment about the shape of a 2nd separate flow path. It is a top view explaining the mode of shock wave propagation at the time of discharge of a liquid. It is a top view explaining the mode at the time of bubble generation. It is a figure which shows the result (photographing result) which confirmed the shock wave reduction by the conventional structure and the structure of a present Example. 6 is a plan view showing a specific structure of a head used in Example 2. FIG. It is a figure which shows the result of having photographed sequentially a mode that a bubble was discharged using the head of the structure of FIG. It is a figure which shows a part of mask figure of the prototype of a head. It is an external appearance perspective view which shows the conventional liquid discharge head. It is sectional drawing which shows the flow-path structure of the head of FIG. It is a figure which shows the result of having photographed the state in which the bubble remained in the common flow path. It is a figure which shows the result of having photographed the state in which the bubble remained at the entrance of the separate flow path. It is a figure which shows the result of having photographed the state which gas entered the liquid chamber from the nozzle.

Explanation of symbols

10 Line head (liquid discharge head)
DESCRIPTION OF SYMBOLS 11 Semiconductor substrate 12 Heating element 13 Barrier layer 13a Liquid chamber 13b Wall 13d 1st separate flow path 13e 2nd separate flow path 17 Nozzle sheet (nozzle layer)
18 Nozzle 19 Head chip U Width of liquid chamber (distance between a pair of walls)
W Channel width of individual channel

Claims (8)

A plurality of staggered arrays are arranged on a semiconductor substrate at a constant pitch P in one direction and adjacent ones are shifted by an interval X (X is a real number greater than 0) in a direction perpendicular to the pitch P direction. A heating element;
A nozzle layer in which nozzles located on the heating elements are formed;
A barrier layer provided between the semiconductor substrate and the nozzle layer;
A liquid chamber formed by a part of the barrier layer and formed by a pair of walls facing each other so as to sandwich the heating element;
The pair of walls of the liquid chamber are formed by extending in a direction substantially perpendicular to the arrangement direction of the heat generating elements, and are arranged on both sides of the liquid chamber so as to communicate with the liquid chamber. A flow path and
The distance U between the pair of walls in the liquid chamber and the channel width W of the individual channel are:
U> W
It is formed so as to satisfy the relation,
The pair of individual flow paths is
A first individual channel connected to the common channel;
The second individual flow path extending to the opposite side across the liquid chamber with respect to the first individual flow path,
A wall is formed along the arrangement direction of the heat generating elements, with a predetermined distance from the tip of the second individual flow path,
The second individual channels of all the liquid chambers are interposed between the wall formed at a predetermined distance from the tip of the second individual channel and the tip of the second individual channel. Communicated,
In the common flow path, a filter comprising a plurality of pillars is provided,
The columns of the filter are arranged at a pitch of 2P in the arrangement direction of the heating elements,
The liquid discharge in which the center of the heating element closer to the filter among the heating elements arranged in a staggered manner and the center of the column are located on the same line in a direction perpendicular to the arrangement direction of the heating elements head. The liquid discharge head according to claim 1,
Of the plurality of liquid chambers, a line connecting the centers of the liquid chambers disposed on the side away from the common flow path, and the wall formed at a predetermined distance from the tip of the second individual flow path, When the distance between is L,
L ≦ 2 × P
A liquid discharge head formed so as to satisfy the above relationship . The liquid discharge head according to claim 1,
The width of the gap between the columns is equal to or less than the channel width W of the first individual channel,
The height of the clearance gap between the said pillars is a liquid discharge head which is below the height of a said 1st separate flow path . The liquid discharge head according to claim 1,
The cross-sectional area of the gap between the columns is a size included in the flow path surface area of the first individual flow path,
The liquid discharge head having a flow path surface area of the first individual flow path having a size included in an opening area of the nozzle . The liquid discharge head according to claim 1 ,
The relationship between the opening diameter Dx of the discharge surface of the nozzle in the nozzle arrangement direction and the opening diameter Dy of the nozzle in the direction perpendicular to the opening diameter Dx is as follows:
Dx ≧ Dy
And
The channel surface shape of the first individual channel is a rectangular shape with a diagonal length of L1,
The cross-sectional shape of the gap between the columns is a rectangular shape with a diagonal length of L2,
And,
Dx>L1> L2
A liquid discharge head formed so as to satisfy the above relationship . The liquid discharge head according to claim 1 ,
A plurality of the semiconductor substrates are arranged in a line along the arrangement direction of the plurality of heating elements,
A liquid discharge head in which a line head is formed by providing the common flow path along the arrangement direction of the semiconductor substrates . The liquid discharge head according to claim 6 ,
A plurality of the semiconductor substrates arranged in a line form are arranged in a line,
A liquid discharge head configured to supply liquids having different characteristics to the plurality of semiconductor substrates in one row and the plurality of semiconductor substrates in another row . A plurality of staggered arrays are arranged on a semiconductor substrate at a constant pitch P in one direction and adjacent ones are shifted by an interval X (X is a real number greater than 0) in a direction perpendicular to the pitch P direction. A heating element;
A nozzle layer in which nozzles located on the heating elements are formed;
A barrier layer provided between the semiconductor substrate and the nozzle layer;
A liquid chamber formed by a part of the barrier layer and formed by a pair of walls facing each other so as to sandwich the heating element;
The pair of walls of the liquid chamber are formed by extending in a direction substantially perpendicular to the arrangement direction of the heat generating elements, and are arranged on both sides of the liquid chamber so as to communicate with the liquid chamber. A flow path and
The distance U between the pair of walls in the liquid chamber and the channel width W of the individual channel are:
U> W
It is formed so as to satisfy the relation,
The pair of individual flow paths is
A first individual channel connected to the common channel;
The second individual flow path extending to the opposite side across the liquid chamber with respect to the first individual flow path,
A wall is formed along the arrangement direction of the heat generating elements, with a predetermined distance from the tip of the second individual flow path,
The second individual channels of all the liquid chambers are interposed between the wall formed at a predetermined distance from the tip of the second individual channel and the tip of the second individual channel. Communicated,
In the common flow path, a filter comprising a plurality of pillars is provided,
The columns of the filter are arranged at a pitch of 2P in the arrangement direction of the heating elements,
The center of the heating element closer to the filter among the heating elements arranged in a staggered manner and the center of the column are located on the same line in a direction perpendicular to the arrangement direction of the heating elements.
A liquid discharge apparatus including a liquid discharge head.