JP2003145768A - Liquid discharge head and liquid discharge recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide continuous printing without 'blanking' due to defective discharge by restricting accumulation/growth/combination of residual bubbles at liquid chambers and liquid channel halfway regions as much as possible and surely securing a refill/supply of ink to discharge openings. SOLUTION: In the liquid discharge head provided with discharge openings for discharging liquid droplets, liquid channels communicating with the discharge openings, liquid chambers for supplying a liquid to the liquid channels, a discharge energy generating means for applying an energy to discharge the liquid inside the liquid channels from the discharge openings, and a substrate where the discharge energy generating means are arranged, there is set a back orifice plate with holes set closer to the side of liquid chambers than the position of the discharge energy generating means by a liquid channel path.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid ejection head for ejecting and recording droplets, a liquid ejection recording apparatus equipped with the same, and a so-called inkjet printer.

[0002]

2. Description of the Related Art Conventionally, as an ink jet printer, a so-called side shooter type in which a substrate on which a discharge energy generating means is arranged and a discharge port portion face each other and an edge shooter type other than this have been commercialized. Further, there are a discharge energy generating means using an electrothermal conversion element and a piezoelectric / electrostrictive element.

[0003]

In any of the methods, an undesired bubble generation is a factor that hinders good droplet ejection.
There is a residual. Generally, the liquid flow path space in which the discharge energy generating means is installed is extremely narrow. On the other hand, looking at the connection between the liquid chamber and the liquid flow path described above, the space suddenly becomes wider with the intention of speeding up the ink refill supply. Due to this influence, an opportunity of forming a so-called negative pressure state occurs at each of the ejection operations at this connection portion. In a so-called bubble jet (registered trademark) type ink jet printer that employs an electrothermal conversion element as a discharge energy generating means, there are generation of accompanying micro bubbles associated with main bubble formation at each discharge operation. Accumulation / growth / coalescence is repeated at the connection between the liquid chamber and the liquid flow path, which tends to occur. Such a situation becomes extremely noticeable in the case of continuous printing for a long time, and residual bubbles that have repeatedly accumulated, grown, and coalesced at the connection part of the liquid chamber and the liquid flow path cut off the refill supply of ink to the ejection port. I will end up.
As a result, there is a problem in that nozzles that do not eject ink normally during printing appear at arbitrary places, and as a result, “missing” occurs in printing.

Up to now, measures have been taken to prevent residual bubbles from adhering to the connection between the liquid chamber and the liquid flow path, and to remove the bubbles from the liquid ejection head to the outside by various suction recovery means. However, these measures are post-processing,
It cannot be a preventive measure for printed matter with "missing". Further, the suction recovery means widely used in the conventional method has a drawback that the recovery is performed while wastefully sucking the ink. In particular, the waste of ink becomes significant when removing the large bubbles that have grown. Further, if the recovery cannot be performed within the designated time, not only the recovery operation is prolonged, but also the amount of ink that is sucked and discharged wastefully increases.

The present invention has been made in view of the above problems, and suppresses accumulation, growth, and coalescence of residual bubbles as much as possible in a liquid chamber or an intermediate region of a liquid flow path to a discharge port. "Removal" by ensuring the refill supply of ink
It is an object of the present invention to provide a liquid ejection head and a liquid ejection recording apparatus that enable clear continuous printing without any trouble.

[0006]

In order to solve the above-mentioned problems, the present invention has the following constitutions (1) to (7).

(1) A discharge port for discharging droplets, a liquid flow path communicating with the discharge port, a liquid chamber for supplying a liquid to the liquid flow path, and a liquid in the liquid flow path for the discharge port. In a liquid ejection head provided with ejection energy generation means for applying energy to eject from the ejection energy generation means, and a substrate on which the ejection energy generation means is arranged, in the liquid flow path, the liquid chamber side is closer to the ejection energy generation means than the ejection energy generation means. A liquid discharge head having a back orifice plate provided with a hole.

(2) The liquid discharge head according to (1), wherein the back orifice plate and the substrate are substantially parallel to each other.

(3) A plane including the ejection port, a plane including the substrate and the back orifice plate are substantially parallel to each other, and the back orifice plate includes the ejection port with the plane including the substrate interposed therebetween. Is installed on the opposite side. The liquid discharge head according to (1) above.

(4) The discharge energy generating means applies heat to the liquid to generate film boiling in the liquid, thereby generating bubbles used for discharging the liquid in the liquid flow path. The liquid discharge head according to any one of (1) to (3) above.

(5) The bubbles are communicated with the atmosphere under the condition that the first derivative of the moving speed of the bubbles in the liquid in the liquid flow path communicating with the discharge port is negative in the discharge direction. The liquid ejection head according to (4) above, which uses a method of ejecting droplets.

(6) A step of deforming a part of a gas-liquid interface between the bubble and the liquid generated in the liquid in the liquid flow path communicating with the discharge port so as to contact the substrate, and the deforming step The liquid discharge head according to (4) above, which uses a discharge method including the step of communicating the bubbles with the outside air after or almost simultaneously.

(7) A driving circuit for giving a signal to the ejection energy means, and a recording medium conveying means for conveying a recording medium to which the ejected liquid is attached are provided. A liquid discharge recording apparatus that performs recording using the liquid discharge head according to any one of (6).

[0014]

According to the above structure, the negative pressure level and the negative pressure region formed at each connection of the liquid chamber and the liquid flow path for each discharge operation are improved. As a result, residual bubbles are unlikely to accumulate, grow, and coalesce in the liquid chamber or the liquid flow passage intermediate region, and it is possible to reliably secure the refill supply of ink to the ejection port and to provide clean continuous printing without "dropout".

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings.

1 to 5 are explanatory views showing a basic form of the present invention. Each of FIGS. 1 to 5 shows an example of the construction of an ink jet head according to the present invention and its manufacturing procedure. Has been done.

First, in the present invention, for example, as shown in FIG. 1, a silicon substrate S1 and a ceramics C are used.
1. Prepare a back orifice plate C2. Ceramics or the like is preferable for the back orifice plate C2. Each silicon substrate S1 and ceramics C1 and back orifice plate C2 have a hole h1 for forming a liquid flow path that leads from the liquid chamber to the discharge port later, a communication flow path shelf 21,
Liquid chambers 22 are provided respectively. Any of known processing methods may be used for drilling these holes. For example, the holes in the silicon substrate S1 may be processed by anisotropic etching or the like. The holes of the ceramics C1 and the back orifice plate C2 are finished by punching, laser processing, etc. (for convenience, FIG. 1 shows the range up to three electrothermal conversion elements for discharge). In addition, these silicon substrates S
1 and the ceramics C1 and the back orifice plate C2 are integrally formed as shown in FIG. 2 by any fastening means or adhesion using an adhesive.

After that, as shown in FIG. 3, a desired number of electrothermal converting elements 3 are arranged on the back orifice plate C2 (surface) through the silicon oxide or silicon nitride layer 2. It should be noted that a control signal input electrode (not shown) for operating these electrothermal conversion elements 3 is connected. Further, generally, various functional layers such as a protective layer are provided for the purpose of improving the durability of the electrothermal conversion elements 3, but it goes without saying that the present invention may be provided with such a functional layer.

Next, the step of forming the nozzle portion on the back orifice plate C2 is started. Here, a manufacturing method using a soluble resin layer will be described as an example. Here, since the upper surface of the back orifice plate C2 is almost flat and a coating means such as spin coating or roll coating can be used, if the film thickness is about 50 μm or less, it can be formed with high accuracy with an arbitrary film thickness. Can be a membrane.

In this way, a resin layer that can be dissolved by spin coating or roll coating is formed on the back orifice plate C2 and patterned to form a liquid flow path pattern. Reference numeral 4 denotes a soluble resin layer forming this liquid flow path pattern.

Next, a coating resin layer 5 is formed as shown in FIG. Since the resin serves as a structural material for an inkjet head, it is required to have characteristics such as high mechanical strength, heat resistance, adhesion to a substrate, resistance to an ink liquid, and no deterioration of the ink liquid.

The coating resin layer 5 is preferably one that is polymerized and cured by application of light or heat energy and strongly adheres to the substrate.

Next, as shown in FIG. 5, the ink discharge port 6 is formed on the coating resin layer 5. As a method of forming the ink ejection port 6, if the coating resin layer 5 is photosensitive, patterning may be performed by a photolithography technique. When the cured resin layer is further processed, methods such as processing with an excimer laser and etching with oxygen plasma may be used.

Next, as shown in FIG. 6, the soluble resin layer 4 forming the liquid flow path pattern is eluted. Members (not shown) for supplying ink and electric connections (not shown) for driving the electrothermal converting element 3 are performed on the silicon substrate S1 having the liquid flow path and the ink discharge port 6 formed in this way. Thus, an inkjet head can be formed.

[0025]

Example 1 In this example, an ink jet head was prepared according to the procedure shown in FIGS.

First, a silicon substrate S1 having a thickness of about 450 to 500 μm, a ceramics C1 having a thickness of about 5 to 20 μm, and a back orifice plate C2 were prepared. The silicon substrate S1, the ceramics C1 and the back orifice plate C2 are perforated by the method described above. Especially the back orifice plate C2
The hole h1 provided in the above is a square hole of 9 μm × 9 μm, and the center of the hole h1 is aligned with the center of the electrothermal conversion element 3 as shown in FIG. 6B. Further, as shown in FIG. 6A, in the cross section including the center of the hole h1 and the center of the electrothermal conversion element 3, the respective dimensions L1, L2, L3, L4 have the following relationship. The hole h1 is provided. L4 is Figure 6
It is the circumscribed width dimension of the two holes shown in (a).

L3> L1 and L3> L2 and L
3 = L4 Others produced the inkjet head by the procedure according to the above-described embodiment. Note that this condition is not limited and may be arbitrarily selected within a range in which the liquid flow path can be secured.

As a result of carrying out continuous solid printing (continuous discharge operation) on A4 size paper using this head, non-discharge due to residual bubbles, that is, "missing" of print does not occur at the 20-sheet level, which is good. A good print was obtained.

Although the hole h1 provided in the back orifice plate C2 is a square hole in the first embodiment, it may be a round hole or another polygonal hole, and the opening area may be arbitrarily selected.

[0030]

Example 2 In this example as well, an ink jet head was manufactured according to the procedure shown in FIGS.

In this embodiment, as shown in FIG.
A back orifice plate C2 provided with holes h1 and h2 so that the two holes h1 and h2 are positioned equidistantly with respect to the center line of the electrothermal conversion element 3 was used. The hole h1,
Both h2 are square holes of 9 μm × 9 μm. Other than that, the ink jet head was manufactured by the procedure according to the above-described embodiment. Other conditions are the same as in Example 1.

As a result of carrying out continuous solid printing (continuous discharge operation) on A4 size paper using this head, non-discharge due to residual bubbles, that is, "missing" of printing does not occur at the 20-sheet level, which is good. A good print was obtained.

Although the holes h1 and h2 provided in the back orifice plate C2 are square holes in the second embodiment,
It may be a round hole or another polygonal hole, and the opening area may be arbitrarily selected.

[0034]

Comparative Example As a head of a comparative example, Japanese Patent Laid-Open No. 09-011
A head having the configuration shown in FIG. 8 was manufactured using the procedure disclosed in No. 479. The driving frequency, the volume of ink droplets to be ejected, and the like were set to be the same as those in Examples 1 and 2.

As a result of carrying out continuous solid printing (continuous discharge operation) on A4 size paper using this head, there is no discharge due to residual bubbles after about 10 sheets, that is, "missing" of printing.
Occasionally occurred, and a suction recovery operation was started.

Immediately after the continuous solid printing (continuous ejection operation) on 20 sheets of A4 size paper, the ink jet head of Example 1 and the ink jet head of Example 2 and immediately after the occurrence of "missing" of printing The inkjet head of the comparative example was observed with a microscope. The observation was made in detail from the side of the orifice plate 5 where a large number of discharge ports were formed. As a result, in the heads of Examples 1 and 2, small residual bubbles were observed, but none of them had a size that hindered ink refill in the ejection port direction. The causes of this difference are considered to be as follows. That is, in the configuration of the inkjet head of the comparative example, during discharge operation (during foaming), a large back area in the direction of the liquid chamber on the surface of the substrate on which the electrothermal conversion element 3 is installed has a large opening area and a large volume directly. It is blowing into the liquid chamber 32. On the other hand, in Examples 1 and 2, the back orifice plate C2 provided with small holes having a small opening area was installed and the curved flow path (communication flow path shelf) 21 was introduced, so that the volume Momentum blowing out into the large liquid chamber 22 is suppressed. As a result, in the first and second embodiments, the negative pressure level and the negative pressure region formed at each connection between the liquid chamber 22 and the liquid flow path are improved, and as a result, the liquid chamber 22 and the liquid flow path are in the middle. It is considered that residual bubbles became difficult to accumulate, grow, and coalesce in the area.

In addition, the communication channel shelf 21 (silicon substrate S) introduced in the heads of the first and second embodiments.
1 A gap formed by the upper surface and the back orifice plate C2. Since there is no threshold in the direction in which the ejection ports are arranged, the ink that has entered the communication channel shelf 21 from another area where ink can be taken in even if there is bubbles at a certain part is stable and the hole h1 of the back orifice plate C2 is stable. , H2 is considered to be supplied to each discharge port. It is also considered that () worked well to secure the ink refill.

Although the side shooter type ink jet head has been described above, the same effect can be obtained for the edge shooter type ink jet head by adopting the configuration shown in FIG.

[0039]

As described above, according to the present invention, the negative pressure level and the negative pressure region formed at each connection between the liquid chamber and the liquid flow path for each discharge operation are improved. As a result, residual bubbles are unlikely to accumulate, grow, and coalesce in the liquid chamber or in the middle of the liquid flow path, the ink refill supply to the ejection port can be reliably ensured, and clean continuous printing without "missing" can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a silicon substrate, a ceramics plate, and a back orifice plate according to the present invention.

FIG. 2 is a cross-sectional view showing a process of forming an inkjet head that is Embodiment 1 of the present invention.

FIG. 3 is a cross-sectional view showing a process of forming an inkjet head that is Embodiment 1 of the present invention.

FIG. 4 is a cross-sectional view showing a process of forming an inkjet head that is Embodiment 1 of the present invention.

FIG. 5 is a cross-sectional view showing a process of forming an inkjet head that is Embodiment 1 of the present invention.

6A is a cross-sectional view of an inkjet head that is Embodiment 1 of the present invention, and FIG. 6B is a main plan view of the inkjet head that is Embodiment 1 of the present invention.

FIG. 7 is a main plan view of an inkjet head that is Embodiment 2 of the present invention.

FIG. 8 is a cross-sectional view of an inkjet head that is a comparative example.

FIG. 9 is a cross-sectional view of an inkjet head of an edge shooter type.

[Explanation of symbols]

S1 Silicon substrate C1 ceramic plate C2 back orifice plate 2 Silicon oxide or silicon nitride layer 3 Electrothermal conversion element 4 Dissolvable resin layer that forms a liquid flow path pattern 5 Coating resin layer (orifice plate) 6 Droplet ejection port (ink ejection port) h1 hole (back orifice plate hole) h2 hole (hole in back orifice plate) 21 communication channel shelf 22 Liquid chamber 32 liquid chamber

Claims (7)

[Claims] 1. A discharge port for discharging droplets, a liquid flow path communicating with the discharge port, a liquid chamber for supplying a liquid to the liquid flow path, and a liquid in the liquid flow path from the discharge port. In a liquid ejection head provided with ejection energy generating means for applying energy to eject and a substrate on which the ejection energy generating means is arranged, in a liquid flow path, a liquid chamber side is closer to the liquid chamber than the ejection energy generating means. , A liquid orifice head having a back orifice plate provided with holes. 2. The liquid ejection head according to claim 1, wherein the back orifice plate and the substrate are substantially parallel to each other. 3. The plane including the discharge port, the plane including the substrate, and the back orifice plate are substantially parallel to each other, and the back orifice plate is a plane including the discharge port sandwiching the plane including the substrate. The liquid ejection head according to claim 1, wherein the liquid ejection head is installed on the opposite side. 4. The discharge energy generating means applies heat to the liquid to cause film boiling in the liquid to generate bubbles used for discharging the liquid into the liquid flow path. The liquid ejection head according to claim 1, wherein 5. A droplet is formed by communicating the bubble with the atmosphere under the condition that the first differential value of the moving speed of the bubble in the liquid in the liquid flow path communicating with the discharge port at the tip of the discharge direction is negative. The liquid ejection head according to claim 4, wherein a method of ejecting is used. 6. A step of deforming a part of a gas-liquid interface between a bubble and the liquid generated in a liquid in a liquid flow path communicating with the discharge port so as to contact the substrate, and a step of the deforming step. The liquid discharge head according to claim 4, wherein a discharge method including a step of communicating the bubbles with the outside air after or substantially simultaneously is used. 7. A drive circuit for giving a signal to the ejection energy means, and a recording medium conveyance means for conveying a recording medium to which the ejected liquid is attached, according to any one of claims 1 to 6. A liquid ejection recording apparatus that performs recording using the liquid ejection head according to any one of items.