JP2002067315A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce occurrence of dent defect portions P due to chipping on the top face edge of an isolating wall 1 made of piezoelectric ceramics when a channel member 3 constituting an ink jet recording head 10 is machined to form the channel, prevent movement of the top face edge of the isolating wall 1 when the movement happens, and control displacement of the isolating wall 1 within a predetermined amount. SOLUTION: An ink jet recording head 10 is composed of plural isolating walls 1 made of piezoelectric ceramics and laid in parallel, the channel member 3 which makes an ink channel 2 by the isolating walls 1, a top plate 5 bonded to the top face of the isolating walls 1, and driving electrodes 4 attached on both sides of each isolating wall 1. When a total area of dent defect portions P existing only on the top face edges of the isolating walls 1 is A, and a total area of the top face of the wall including the dent defect portions P is B, A/B×100 is equal or less than 10%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head mounted on an ink jet recording apparatus used for printing characters and images.

[0002]

2. Description of the Related Art In recent years, with the spread of personal computers and the development of multimedia, ink jet recording apparatuses have been rapidly expanding as recording apparatuses for outputting information to a recording medium.

As an ink jet recording head (hereinafter referred to as a head) mounted on an ink jet recording apparatus, a fine heater is provided in a flow path filled with ink, and the heater heats and boil the ink. And a thermal jet method in which ink in the flow path is pressurized by bubbles generated in the flow path and ink droplets are ejected from the ink ejection holes, and a partition wall forming a flow path filled with ink is bent and displaced by a piezoelectric element. In general, a piezoelectric method in which ink in a flow path is mechanically pressurized and ink droplets are ejected from an ink ejection hole is used. Among these, the piezoelectric method is excellent in durability and responsiveness, and directly ejects ink. Since there is no heating, there is an advantage that the type of ink is not limited.

As shown in FIG. 6, such a piezoelectric head has a plurality of partition walls 41 arranged side by side. A flow path member 43 made of a piezoelectric ceramic having one end closed and a top plate 45 having an ink supply hole 46 bonded to the top surface of each partition 41 via an adhesive layer 51 and communicating with each flow path 42. And a nozzle plate 48 having an ink discharge hole 47 connected to one end of the flow path member 43 via an adhesive layer (not shown) and communicating with each flow path 42.
In the upper half of both side surfaces of No. 1 there was a drive electrode 44 formed along the longitudinal direction thereof (Japanese Patent Laid-Open No. 7-1).
01,056). 49 is the driving electrode 44
Are connected to an external circuit, and each partition 41 is polarized in the direction of the arrow.

In order to print on a recording medium using the head 50, when a voltage is applied between driving electrodes 44 formed on both side surfaces of the partition wall 41, the piezoelectric ceramics forming the partition wall 41 are sheared. Since the mode is deformed and each partition 41 is bent and displaced in a substantially rectangular shape, the displacement of the partition 41 pressurizes the ink in each flow path 42 and discharges ink droplets from the ink discharge holes 47. .

In order to manufacture such a head 50, for example, a diamond ceramic is fixed to a piezoelectric ceramic plate whose thickness has been adjusted by grinding and which has been polarized in the thickness direction. By arranging a plurality of grooves in parallel using a blade, each groove is used as an ink flow path 42, and a flow path member 43 is formed in which a wall separating each groove is a partition 41,
Next, a driving electrode 44 is formed on the upper half of both sides of the partition wall 41 by a thin film forming means such as a vapor deposition method or a sputtering method, and a wiring 49 of the driving electrode 44 is formed from the rear end of the flow path 42 to the end of the flow path member 43. Are adhered to each other, a top plate 45 having an ink supply hole 46 is adhered to the top surface of each partition 41 via an adhesive layer 51, and an adhesive layer (not shown) is attached to the open end of the flow path member 43. ), The nozzle plate 48 provided with the ink discharge holes 47 is bonded.

[0007]

However, in manufacturing the above-described flow path member 43 of the ink jet recording head 50, the piezoelectric ceramic is brittle as compared with insulating ceramics or the like. When the groove is formed, chipping occurs at the top surface edge portion of the partition wall 41 due to processing pressure with the rotary blade and the like, and a concave notch is formed. There is a problem that the rigidity of the entire adhesive layer 51 for fixing the surface to the top plate 45 is reduced. As a result, the driving electrode 44
When the partition wall 41 is deformed in the shear mode by applying current to the partition wall 41, the top of each partition wall 41 moves, and the partition wall 41 cannot be driven with a predetermined displacement amount.
2, the pressure applied to the ink in the ink ejection holes 4 decreases.
7, the ejection speed of the ink droplets ejected from the nozzle 7 could not be increased.

Further, if the concave portion formed at the top surface edge of the partition wall 41 is large, the flow of ink in the flow path 42 is disturbed, and stable ejection of ink droplets is hindered. Air bubbles in the ink adhere to the existing portion and flow path 4
2 and the ink droplets may be disturbed.

Further, if the proportion of the concave portion formed at the top surface edge of each partition wall 41 becomes too large, the adhesive layer 64 may be peeled off when the partition wall 41 is displaced because the adhesive strength is low.

In order to solve such a problem, it is conceivable to increase the amount of the adhesive applied between the top surface of the partition wall 41 and the top plate 45.
When the drive electrode 44 is energized and the partition 41 is deformed in the shear mode, the top of the partition 41 moves, and the partition 41 is driven with a predetermined displacement because the thickness of the partition 1 is easily increased and elastically deformed. When the amount of the adhesive is large, the adhesive may adhere to the side surface of the partition wall 41. In this case, the flow of the ink in the flow channel 41 is obstructed and the communication with each flow channel 41 is prevented. In addition, there is a possibility that ink droplets ejected from the ink ejection holes 47 may vary, and if the adhesive adhering to the side surface of the partition wall 41 peels off, the ink ejection holes 47 may be clogged.

[0011]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention has a plurality of partition walls made of piezoelectric ceramics arranged side by side, and a flow path member which serves as an ink flow path between the partition walls. A top plate adhered to a surface of the partition wall, and drive electrodes provided on both side surfaces of the partition wall, and the drive electrodes are energized to bend and displace the partition wall, thereby causing ink discharge communicating with the flow path. In the ink jet recording head that ejects ink droplets from the holes, the area occupied by the concave notch existing only at the top surface edge of the partition is A, and the area of the entire top surface of the partition including the concave notch is B. A / B x 100 is 10%
It is characterized by the following.

[0012]

Embodiments of the present invention will be described below.

FIG. 1 is a partially cutaway perspective view showing an example of an ink jet recording head according to the present invention, and FIG.
(B) is a partial cross-sectional view for explaining the principle of driving the inkjet recording head according to the present invention.

In the ink jet recording head 10 (hereinafter, referred to as a head), a plurality of partition walls 1 are arranged in parallel at equal intervals. A flow path member 3 made of piezoelectric ceramics having one end closed, a top plate 5 having an ink supply hole 6 adhered to the top surface of the partition 1 via an adhesive layer 11 and communicating with each flow path 2; A nozzle plate 8 having an ink discharge hole 7 which is adhered to the open end side of the flow path member 3 via an adhesive layer (not shown) and which communicates with each flow path 2; The drive electrode 4 is formed on one half along the longitudinal direction.

The piezoelectric ceramics forming the flow path member 3 include piezoelectric ceramics mainly composed of lead zirconate titanate (PZT type) and lead magnesium niobate (PMM).
Piezoelectric ceramics whose main component is N-based), piezoelectric ceramics whose main component is lead nickel niobate (PNN-based), and piezoelectric ceramics in which these main components are combined can be used.

The flow path member 3 is formed with a plurality of grooves to be flow paths 2 by grinding a piezoelectric ceramic plate using a rotary blade in consideration of mass productivity, workability, and the like, as described later. At this time, a force given by the runout of the rotary blade or the like, or a force generated by the processing powder biting between the partition 1 and the rotary blade, causes the top surface edge of the partition 1 to be formed. The generated chipping is minimized. The area occupied by the concave notch P existing only at the top surface edge of the partition 1 is A, and the total area of the top surface of the partition 1 including the concave notch P is B. A / B × 100 is set to 10% or less, preferably 5% or less.

Reference numeral 9 denotes wiring for connecting the driving electrode 4 to an external circuit. Each partition 1 is polarized in the direction of the arrow, and the driving electrodes formed on both side surfaces thereof are provided. When current is applied between the four, the piezoelectric ceramics forming the partition wall 1 undergoes shear mode deformation.

A recording medium using the head 10
In order to print on the lower electrode (shown below), first, an ink such as a pigment-type oil-based ink, a water-based dye ink, or an ultraviolet curable ink is introduced into each flow path 2 from the ink supply hole 6, and, for example, the driving electrodes 4b, 4c and drive electrodes 4h, 4
i to the positive electrode voltage, and drive electrodes 4a, 4d, 4g,
When the voltage of the negative electrode is applied to 4j, the partition walls 1a and 1b are bent and displaced toward the flow path 2a and the partition walls 1d and 1e are bent and displaced toward the flow path 2d as shown in FIG. By pressurizing the ink filled in the paths 2a and 2d,
Ink droplets can be ejected from the ink ejection holes 7. Next, when energization to each of the driving electrodes 4a to 4d and 4g to 4j is interrupted, the partition walls 1a, 1b, 1d,
1e returns to the original shape by the elastic action, and the flow paths 2a, 2
As a result, the introduction of ink from the ink supply hole 6 is started, and the drive electrode 4
When a voltage is applied to the electrodes a to 4d and 4g to 4j with the polarity reversed, the partition walls 1a and 1b are separated from the flow path 2a as shown in FIG.
Bends outward with respect to, and the partition walls 1d, 1e
Is bent outwardly with respect to the flow path 2d.
The inside of a and 2d is further decompressed and filled with ink. Then, the driving electrodes 4a to 4d, 4g to 4j
When the power to the power supply is cut off, the partition walls 1a and 1
b, 1d, and 1e return to their original shapes by the elastic action and enter the next ink droplet ejection stage. By repeating these operations sequentially, the ink droplets can be ejected continuously. It has become.

According to the present invention, the area occupied by the concave portion P formed at the edge of the top surface of each partition 1 is A, and the area of the entire top surface of the partition 1 including the concave portion P is B. When
Since A / B × 100 is set to 10% or less, a decrease in the contact area with the top plate 5 can be suppressed, and sufficient adhesive strength and rigidity can be ensured. Even if the top of the partition 1 is firmly fixed, the partition 1 can be driven with a predetermined displacement.

That is, the present inventor conducted various studies on the development of the ink jet recording head 10 and found that
In the grinding process at the time of forming the groove serving as the flow path 2, if the proportion of the concave portion P formed on the top edge of the partition wall 1 is large, the bonding area between the partition wall 1 and the top plate 5 is reduced, so that the bonding is performed. It has been found that the rigidity of the layer 11 is reduced, and the displacement of the partition 1 is adversely affected. Therefore, in recent years, the size (width 40) of the partition 1 employed in the ink jet recording head 10 has been increased.
~ 100μm, height 250 ~ 500μm, length 0.6 ~
10 mm), the material, and the power given to the partition 1 were repeated, and the experiment was repeated. As a result, the area occupied by the concave notch P existing only at the top edge of the partition 1 was A, and the concave notch P was defined as A / B, where B is the area of the entire top surface of the partition 1 including
If 100% is set to 10% or less, the adhesion layer 11
Can obtain sufficient adhesive strength and rigidity, and the partition 1 and the top plate 5 can be firmly fixed. If the partition 1 is displaced, it can be driven with a predetermined displacement amount, It has been found that a decrease in the ejection speed of ink droplets ejected from the ink ejection holes 7 can be reduced, and accurate characters and images can be printed according to information.

Further, since the number of the concave portions P existing at the top surface edge of the partition wall 1 is reduced, the ink droplets can be stably ejected without disturbing the flow of the ink in the flow path 2. Since the bubbles in the ink hardly adhere to the portion where the notch P exists, it is also possible to prevent the discharge characteristics of the ink droplet from being hindered by the bubbles remaining in the flow path 2.

In the present invention, the notch P which exists only at the edge of the top surface of the partition 1 is defined as shown in FIG.
The chipping or shedding portion present on the ridge formed by the top surface and the side surface of the partition 1 is defined as an area A occupied by the concave portion P.
Is the sum of the areas of the respective concave notches P existing only at the top surface edges when viewed from above the top surface of the partition wall, and the area B of the entire top surface of the partition wall 1 including the concave notches P , The area of the entire top surface of the partition 1 without the concave notch P.

On the other hand, it is preferable to use a thermosetting adhesive as an adhesive for adhering the partition wall 1 and the top plate 5, specifically, an epoxy-based adhesive, a polyimide-based adhesive, and a phenol-based adhesive. Among them, it is preferable to use an epoxy-based adhesive from the viewpoint of the curing temperature.

The thickness of the adhesive layer 11 for adhering the partition 1 and the top plate 5 is preferably as thin as possible from the viewpoint of securing rigidity, and is preferably several μm to 10 μm. That is, if the thickness of the adhesive layer 11 exceeds 10 μm, sufficient rigidity cannot be obtained even when the above-mentioned adhesive is used, and when the partition 1 is displaced, the top of the partition 1 moves due to the elastic action of the adhesive layer 11. This is because the partition wall 1 cannot be displaced by a predetermined displacement amount because it becomes easy, and conversely, it is difficult to make the thickness of the adhesive layer 11 less than several μm in manufacturing.

In order to manufacture such a head 10, a piezoelectric ceramic mainly composed of lead zirconate titanate (PZT) and a lead magnesium niobate (PMN based) which have been subjected to a polarization treatment in the thickness direction in advance. ), A piezoelectric ceramic mainly composed of lead nickel niobate (PNN-based), and a piezoelectric ceramic plate composed of a piezoelectric ceramic in which these main components are combined.

Next, a plurality of grooves, one end of which is closed, are ground using a rotary blade having diamond abrasive grains fixed to the piezoelectric ceramic plate, and each groove is used as an ink flow path 2.
The channel member 3 is manufactured by using the partition wall 1 as a partition wall for each groove. At this time, the area occupied by the concave notch P existing only at the top edge of the partition wall 1 is represented by A, and the concave notch P When the area of the entire top surface of the partition wall 1 including B is defined as B, A / B × 100 (the occupied area ratio of the recessed portion) is set to 10% or less.

In order to set the occupied area ratio of the concave notch P in the above-described range, the diamond abrasive adhered to the rotary blade has a count of # 1200 (diamond abrasive having a particle diameter of 6
１２12 μm) to # 2500 (diameter of diamond abrasive grains is 4 to 6 μm), and the peripheral speed of the rotary blade is 2,000 m / min to 6000 m / min.
Processing speed 15 mm / sec or less, preferably 5 mm / s
It is important to cut under the condition of ec or less.

That is, the count of the diamond abrasive grains is # 120.
If the diameter is smaller than 0, the processing pressure applied to the partition wall 1 is large because the diamond abrasive grains are large, and chipping easily occurs. On the contrary, the count of the diamond abrasive grains is # 250.
If it is larger than 0, the diamond abrasive grains become too fine and the grinding ability is extremely reduced, resulting in poor processing efficiency.

The peripheral speed of the rotary blade is 2000 m / min.
If the rotation speed of the rotary blade is less than 6000 m, the peripheral speed of the rotary blade is 6000 m.
If the speed exceeds / min, the run-out (vibration) of the rotary blade becomes large, and the rotary blade hits the partition wall 1 to easily cause chipping.

Further, the reason why the processing speed is set to 15 mm / sec or less is that when the processing speed exceeds 15 m / sec, the processing speed exceeds the grinding ability of the rotary blade, and the rotary blade moves to the edge of the top surface of the partition wall 1. Processing pressure by
This is because chipping is likely to occur.

Next, after masking the required portions of the obtained flow channel member 3, platinum, gold, palladium, rhodium, nickel, nickel, Metal such as aluminum, or platinum
An alloy mainly composed of gold, palladium-silver, platinum-palladium, or the like is applied by a film forming means such as a vapor deposition method, a sputtering method, or a plating method to form the driving electrode 4 and from the end of the flow path 2 Platinum, also at the rear end of the flow path member 3
A metal such as gold, palladium, rhodium, nickel, or aluminum, or an alloy mainly composed of platinum-gold, palladium-silver, platinum-palladium, or the like is deposited by a film forming means such as an evaporation method, a sputtering method, or a plating method. Thus, the wiring 9 of the driving electrode 4 is formed.

Thereafter, an adhesive is applied to the top surface of each partition wall of the flow path member 3 and the open end face of the flow path member 3, and then the flow path 3
Made of an insulating material such as ceramics, glass, silicon, or an insulated metal to cover the top of the
A top plate 5 having an ink supply hole 6 for introducing ink into each flow path 2 is brought into contact with and bonded to each partition 1,
A nozzle plate 8 made of ceramics, glass, silicon, resin, metal, or the like, and provided with an ink discharge hole 7 for discharging ink in the name flow path 2 is used to cover the open end of the flow path member 3. The head 10 shown in FIG. 1 can be obtained by making contact with and bonding to the open end face of the head 3.

Although the embodiment of the present invention has been described above, the present invention is not limited to the head 10 shown in the embodiment. For example, in the head 10 shown in FIG. Although an example in which the whole is formed of piezoelectric ceramics has been described, only the partition wall 1 may be formed of piezoelectric ceramics, and as shown in FIG.
The nozzle plate 8 in FIG. 1 is a lid plate 8 having no ink discharge holes 7, the head plate 5 is provided with the ink discharge holes 7, and the ink supply holes 6 are provided at the bottom of the flow path member 3. As shown in FIG. 5, a wall member made of piezoelectric ceramics that has been polarized in the opposite direction is adhered to the top of each partition 1 in FIG. Needless to say, improvements and changes can be made without departing from the gist of the present invention, such as a head having a ridge formed thereon. Particularly, in the head shown in FIG. 1 can be bent and displaced in a substantially rectangular shape around the bonding portion, and the ejection speed of ink droplets can be increased as compared with the head 10 shown in FIG. 1, which is preferable.

Further, in the present embodiment, the description has been made by focusing on the concave notch portion P existing at the top edge portion of the partition wall 1 which greatly affects the displacement amount of the partition wall 1. However, the partition wall bonded to the nozzle plate 8 is described. Needless to say, it is more preferable that the occupied area ratio at the edge portion of the first end surface is also within the range of the present invention.

[0035]

EXAMPLE A piezoelectric ceramic plate containing lead zirconate titanate as a main component, which had been polarized in the thickness direction in advance, was prepared, and a groove having a groove width of 75 μm was formed using a rotary blade having diamond abrasive grains fixed thereto.
Groove processing with a groove depth of 350 μm and a pitch of 141 μm,
A plurality of grooves obtained by the groove processing were used as ink flow paths, and a flow path member having a wall partitioning each groove as a partition was manufactured.

At this time, the grain size of the diamond abrasive grains adhered to the rotary blade, the peripheral speed of the rotary blade, and the processing speed are varied, and the size of the concave notch formed at the top edge of the partition wall made of piezoelectric ceramics is varied. The amount was changed, and the occupied area ratio of the recessed portion (A / B × 100) was measured.

The occupied area ratio of the concave notch (A / B × 10
In the measurement of 0), after taking photographs of the top surfaces of arbitrary 10 rows of partition walls for one flow path member, the area occupied by the concave notch portion was measured by an image recognition device, and the average value A was calculated as
The value divided by the area B of the entire top surface of the partition wall including the concave notch is 100
Was calculated.

Next, a driving electrode made of aluminum is formed along the longitudinal direction of the upper half of each side wall of the partition wall of each flow path member by a sputtering method from the rear end of the flow path to the end of the flow path member. Wirings for driving electrodes made of aluminum were formed by sputtering. The size of the driving electrode is 200 μm in the depth direction of the flow path.
m, a band shape in which the longitudinal dimension of the flow channel was 10 mm.

Thereafter, a top plate made of alumina ceramic having ink supply holes is adhered to the top surface of the partition wall via an adhesive layer (5 μm in thickness) made of an epoxy-based adhesive. A test head was manufactured by bonding a nozzle plate made of a polyimide resin having an ink discharge hole to the open end via an adhesive layer (thickness: 5 μm) made of an epoxy-based adhesive.

Then, the speed of the ink droplets discharged from each of the manufactured heads was measured using a high-speed video camera and a strobe, and the discharge speed of the ink droplets was 6 m / sec or more required today. Were judged good.

The drive electrode of the partition had a drive frequency of 120 kHz, the input on the minus side was cut off, and a sine wave voltage of 30 V was applied only on the plus side to eject ink droplets.

The results are as shown in Table 1.

[0043]

[Table 1]

As a result, as can be seen from Table 1, the occupied area ratio (A / B × 1) of the recessed portion existing at the top edge of the partition wall.
00) is set to 10% or less, the ejection speed of the ink droplets becomes 6%.
m / sec or more, and the ink droplet ejection speed required for today's ink jet recording heads can be obtained. In particular, the occupied area ratio (A / B × 100) of the recessed portion is 5% or less. Then, the ejection speed of the ink droplet is 6.5 m / s
ec or more, which was excellent.

[0045]

As described above, according to the present invention, a plurality of partition walls made of piezoelectric ceramic are juxtaposed, and a flow path member having an ink flow path between the partition walls is bonded to the top surface of the partition walls. A drive electrode is provided on each of both side surfaces of the partition wall, and the drive electrode is energized to bend and displace the partition wall so that the ink is discharged from the ink discharge hole communicating with the flow path. In the ink jet recording head for discharging droplets, A is the area occupied by the concave notch existing only at the top surface edge of the partition, and B is the area of the entire top surface of the partition including the concave notch.
When A / B × 100 is set to 10% or less, the reduction of the bonding area between the partition and the top plate is suppressed, the rigidity of the adhesive layer is secured, and the partition and the top plate are firmly connected. When the drive electrode is energized, the partition wall can be bent and displaced by a predetermined displacement amount, so that the ink droplet ejection speed can be improved, and accurate information-based characters can be fixed. And images can be printed.

Further, since the number of the recessed portions existing at the top surface edge of the partition wall is reduced, the ink can be stably ejected without disturbing the flow of the ink in the flow path. The effect of reducing the adverse effects such as the bubbles in the ink adhering to the portion where the recessed portion is present and remaining in the flow path and inhibiting the ejection of the ink droplets can be obtained.

[Brief description of the drawings]

FIG. 1 is a partially broken perspective view showing an example of an ink jet recording head according to the present invention.

FIGS. 2A and 2B are partial cross-sectional views for explaining the driving principle of an ink jet recording head according to the present invention.

FIG. 3 is a partial plan view of a flow path member constituting the inkjet recording head according to the present invention.

FIG. 4 is a perspective view of another example of the ink jet recording head according to the present invention, in which a portion-is broken.

FIG. 5 is a perspective view showing still another example of the inkjet recording head according to the present invention, in which a portion-is broken.

FIG. 6 is a perspective view showing a conventional ink jet recording head, in which a portion-is broken.

[Explanation of symbols]

1, 41: partition wall 2, 42: flow path 3, 43: flow path member 4, 44: drive electrode 5, 45: top plate 6, 46: ink supply hole 7, 47: ink discharge hole 8, 48: nozzle Board 9, 49: Wiring 10, 50: Inkjet recording head 11, 51: Adhesive layer A: Area occupied by concave notch existing only at top edge of partition B: Top of partition including concave notch Total area P: recessed part

Claims (1)

[Claims] 1. A partition member comprising: a plurality of partition walls made of piezoelectric ceramics arranged side by side; a flow path member having an ink flow path between the partition walls; and a top plate adhered to a top surface of the partition walls. A drive electrode is provided on each of both side surfaces of the ink jet recording head that discharges ink droplets from ink discharge holes communicating with the flow path by applying a current to the drive electrode to bend and displace the partition. When the area occupied by the concave notch existing only at the top surface edge of the partition is A and the area of the entire top surface of the partition including the concave notch is B, A / B × 100 is 10% or less. An ink jet recording head, characterized in that: