JP3414905B2 - Recording head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording head, and more particularly to an ink jet recording head, but is also suitable for use in, for example, a fluid element, a micropump, a microvalve, or the like. It has various electrostrictive actuators.

[0002]

2. Description of the Related Art FIG. 4 is a partial structural view of a conventional pressure-on-demand multi-head, and FIG.
4B is a sectional view taken along the line BB in FIG. 4A, in which 31 is a substrate, 32 is a common liquid chamber, 33 is an ink pressurizing chamber, 34 is a fluid resistance portion, and 35 is ink. Supply hole, 36 is a nozzle plate, 37 is a nozzle, 38 is a side wall, 39 is a vibrating plate, 4
Reference numeral 0 is an electrostrictive actuator, and 41 is a recording paper.

A plurality of ink pressurizing chambers 3 of the same shape are formed on the substrate 31.
3 are divided in parallel by the side wall 38 and are arranged in parallel. The ink pressurizing chamber 33 is a portion that serves as an ink flow path and is pressed by the ink for ejecting the ink. One end side of the common liquid chamber 32 has a fluid resistance portion 34 having a narrow flow path cross section.
Connected with. A nozzle plate 36 is joined to the other end side of the pressurizing chamber 33 of the substrate 31, and a nozzle 37 corresponding to each pressurizing chamber 33 is provided.

The upper surface of the pressurizing chamber 33 is open,
The opening is sealed by a thin diaphragm 39, and the diaphragm 3
An electrostrictive actuator 40 is bonded to the upper surface of the pressure applying chamber 33, and by applying a voltage pulse, the vibration plate 39 is displaced toward the bottom of the ink pressurizing chamber 33, for example.
The inside is pressurized, ink droplets are ejected from the nozzles 37, and the ink droplets are attached to the recording medium 41 arranged facing the nozzles 37 for recording.

In the conventional pressure-on-demand multi-head shown in FIG. 4, the electrostrictive actuator 40 is of a pressure pulse system called a plate-type cyclonics system. Generally, the electrostriction actuator 40 is called a pressure pulse system. As a method of applying a pressure pulse to ink by using an actuator or a heating element and ejecting ink particles, in the method of using the electrostrictive actuator, in addition to the cyclonics method, a vibrator cylinder type Zoltan or Gould method or , The ink flow path supplied from the common liquid chamber is provided between the pressurizing chamber and the nozzle, and the pressurizing chamber is driven by a flat electrostrictive element.
In the case of using a heating element, a heating element is provided in the flow path near the nozzle to heat and vaporize the ink in the flow path near the heating element and eject the ink droplets by the pressure of the generated bubbles. A vaporization type valve jet method has been devised.

In addition to this, many methods such as a super jet method using solid ink, an electroosmosis method, a spray gun method, and a mechanical shutter method have been proposed and prototyped. Further, in Japanese Patent Laid-Open No. 63-307969, a beam is deflected by an electrostatic force to close a nozzle to form a so-called valve, and this valve is controlled to let a gas flow of a sublimable dye flow in and out. Further, an elastic movable portion is provided in the liquid chamber, the first electrode is arranged in the elastic movable portion, and a voltage is applied between the elastic movable portion and the second electrode provided on the inner wall of the liquid chamber to deform the elastic movable portion. Then, a method of ejecting a droplet from a nozzle has also been proposed.

[0007]

However, the multi-head using the conventional electrostrictive actuator by the piezoelectric element requires an electrostrictive actuator of a certain size to obtain the ejection output of ink. However, it was not suitable for high density. Further, the response frequency at the time of ink dropping is low, and various improvements have been made to cover this point, such as multiple heads and the use of an air flow system, but the structure is complicated and large. On the other hand, in the conventional method using the drive source by electrostatic force, the drive force is very small, and the cost for obtaining a predetermined drive force, or if an auxiliary structure is required, high density, workability, etc. There were difficulties. SUMMARY OF THE INVENTION The present invention has been made for the purpose of providing a recording head that realizes a high density and an increase in the driving force of an electrostrictive actuator that obtains a sufficient ink ejection output in order to solve the above problems. Is.

[0008]

According to a first aspect of the present invention, there is provided a vibrating member which is provided in at least a part of a flow path forming member which constitutes a flow path of a recording body, and the vibrating member which is provided above the vibrating member. A substrate provided to face each other with a space, a first electrode and a second electrode provided on respective surfaces of the vibrating member and the substrate facing each other, and the first electrode and the second electrode. A dielectric material filled in the gap is used, and when a voltage is applied between the first electrode and the second electrode, the dielectric material causes body expansion to displace the vibrating member. A strain actuator is provided, and the vibrating plate is displaced by using the electrostrictive actuator to reduce the volume of the flow channel to increase the pressure inside the flow channel, and to give kinetic energy to the recording medium to perform the recording. The body is ejected, and the recording medium is attached to the recording medium to achieve high density. To be recorded in the recording medium having a sufficiently large injection force.

According to a second aspect of the present invention, the dielectric substance is a ferroelectric liquid crystal that is oriented obliquely with respect to a direction perpendicular to the surfaces of the first electrode and the second electrode, and the electrostrictive actuator is used. By sandwiching and sealing the ferroelectric liquid crystal between the first electrode and the second electrode, high density recording is possible and high driving force can be obtained.

According to a third aspect of the present invention, there is provided a first electrostrictive actuator provided in a pressurizing chamber constituted by a variable volume portion in the flow passage, and the pressurizing chamber is provided on a side opposite to the recording medium ejecting nozzle. And a second electrostrictive actuator that is provided in the fluid resistance part of the fluid resistance part for varying the fluid passage area of the fluid resistance part and makes the fluid resistance of the fluid resistance part variable. Prior to this, the second electrostrictive actuator is operated to increase the fluid resistance of the fluid resistance portion, so that the internal pressure of the pressure chamber increases and the recording medium in the pressure chamber flows out to the fluid resistance portion side. By preventing this, the pressurizing efficiency of the pressurizing chamber is improved.

[0011]

FIG. 1 is a diagram for explaining an example of an embodiment of a recording head according to the present invention, and FIG.
1A is a plan view, and FIG. 1B is a sectional view taken along the line BB in FIG. 1A. In the figure, 1 is a bottom plate, 2 is a common liquid chamber, 3 is an ink flow path (pressurized liquid chamber). ) 4, fluid resistance portion, 5 side wall, 6 nozzle plate, 7 nozzle, 8 ink supply port, 9 electrostrictive actuator, 10 vibrating plate, 11 dielectric material, 12 upper substrate, 13 Individual electrodes, 14 is a common electrode, 15 is a driving power source, and 16 is a recording medium.

The side wall 5 forming the ink flow path 3 which also serves as a plurality of ink (recording body) pressurizing chambers, and the housing of the recording head including the common liquid chamber 2 and the fluid resistance portion 4 are subjected to a photolithography process. , Si by etching method
It is prepared from a substrate or a product obtained by processing using a ceramic precursor called a green sheet and then firing. In addition, the upper portion of the ink flow path 3 is open,
The lower part is closed by a bottom plate 1, and a nozzle 7 provided on a nozzle plate 6 is provided at one end of the ink flow path 3 and an ink path reaching the common liquid chamber 2 is provided at the other end via a fluid resistance portion 4. It is provided. Ink (recording medium) is supplied to the common liquid chamber 2 from an ink tank (not shown) through a liquid supply pipe (not shown) connected to the ink supply port 8.

The upper opening of the ink flow path is sealed by an electrostrictive actuator 9. The electrostrictive actuator 9 has a thin plate-shaped vibrating plate 10 having an outer shape capable of sealing the upper opening of the ink flow path 3, and a vibrating plate 10 provided on the vibrating plate 10 with a slight gap. Electrodes are provided on the inner surfaces of the vibrating plate 10 and the upper substrate 12 that face each other, and the electrodes on the vibrating plate 10 side correspond to the flow paths 3. With the individual electrode 13,
The electrode on the side of the upper substrate 12 is the common electrode 14 formed in a planar shape. A dielectric material 11 is filled in the gap between the diaphragm 10 and the upper substrate 12.

Between the selected individual electrode 13 and common electrode 14 of the electrostrictive actuator 9 thus constructed,
When a voltage pulse from the driving power supply 15 is applied, the dielectric substance 11 is electrically polarized and changes in volume. Since the upper substrate 12 has a high rigidity, the dielectric material 11 pushes down the vibration plate 10 to reduce the volume in the ink flow path 3 to give a pressure change to the ink, eject an ink droplet from the nozzle 7, and eject the ink onto the recording medium 16. Ink is attached (corresponding to claim 1). The dielectric substance 11 here is preferably a material having a large rate of change in volume upon application of a voltage, and a strong induction liquid crystal is suitable as such a material. The ferroelectric liquid crystal cell that constitutes the electrostrictive actuator will be described below.

FIG. 2 is a view for explaining a structural example of the embodiment of the electrostrictive actuator according to the present invention.
2A is a plan view and FIG. 2B is a view BB of FIG. 2A.
FIG. 2 is a partial sectional view taken along the line, in which 17 is an alignment film, 18 is an encapsulation port, and parts having the same functions as in FIG. 1 are denoted by the same reference numerals as in FIG. The diaphragm 10 is, for example, a thin substrate of ceramics typified by PZT or ZrO ₂ having a thickness of 15 μm, and the upper substrate 12 is a thick substrate of Corning 7047 glass having a thickness of 1.1 mm. Since the upper substrate 12 has a sufficiently large strength as compared with the diaphragm 10, most of the volume change of the ferroelectric liquid crystal 11 obtained by applying a voltage is transmitted to the diaphragm 10. ITO transparent electrodes for voltage application are provided on the inner surfaces of the substrates such as the upper substrate 12 and the vibrating plate 10 which constitute these liquid crystal cells so as to face each other. Is provided with individual electrodes 13 having a pitch and width corresponding to the position where the electrostrictive actuator is arranged. Since a lead wire for external connection is connected to the common electrode and the individual electrode 13, the electrostrictive actuator has a space for taking out the lead wire.

An alignment film 17 is formed on a portion of the vibration plate 10 having the upper substrate 12 having the common electrode 14 and the individual electrode 13 in contact with the ferroelectric liquid crystal 11. The alignment film 17 is formed by lapping an amide polymer or obliquely vapor-deposited SiOx, and the needle crystals are aligned in a certain direction at an angle of 10 ° with respect to the vertical direction of the substrate. Is formed.

The ferroelectric liquid crystal 11 sandwiched between the vibrating plate 10 having the electrodes of this structure and the upper substrate 12 is 4-decyloxybenzylidene-4'-amino-2-methylbutyl cinnamate (DOBAMBC). A representative smectic C is used. Here, in particular,
ZLI3488 (Pitch = 10 μm), ZL manufactured by Merk
I3654 (pitch = 5 μm) was used. A liquid crystal cell is produced in which the relationship between the pitch p of the ferroelectric liquid crystal 11 and the thickness D of the cell gap 19 is D / p = 0.2 to 0.5.

Ferroelectric liquid crystal 11 which is thus oriented.
Since the directions of the polarization vectors are aligned along the helical structure of the liquid crystal itself, the spontaneous polarization becomes larger than that when randomly sandwiched between the substrates. As the cell gap 19, a mylar material is used to obtain a desired cell thickness D and to prevent resonance or crosstalk between the vibration units located on adjacent flow paths. Ferroelectric liquid crystal 11
The relative permittivity of is about 20 to 50, and the desired amplitude of the diaphragm 10 cannot be obtained without the orientation treatment.

When injecting the ferroelectric liquid crystal 11 from the filling port 18, the liquid crystal is heated in a reduced pressure environment to change the liquid crystal from the smectic state to the isotropic state,
The sealing port 18 of the liquid crystal cell is brought into contact with the liquid crystal, and then the environment is returned to atmospheric pressure to inject and seal by utilizing the pressurization of the atmosphere and the capillary phenomenon. Since the isotropic point is around 80 ° C., the liquid crystal is heated to about 100 ° C. After the injection, the material is gradually cooled to obtain a desired alignment state. The ferroelectric liquid crystal 11 that has returned to room temperature has a high viscosity and is almost wax-like.

In the ink jet recording head having such a structure, when a voltage is applied between the individual electrode 13 and the common electrode 14, the polarization vector of the ferroelectric liquid crystal 11 becomes
In order to change the direction of the electric field, the liquid crystal molecules themselves are also displaced in that direction. Now, in the liquid crystal cell of this configuration, the ferroelectric liquid crystal 11 has a spiral direction from the direction perpendicular to the substrate 10
Since the orientation is inclined, the displacement occurs in the direction perpendicular to the substrate (electric field direction). The displacement thus generated is transmitted to the substrate of the individual electrode 13 which is the vibration plate 10,
The diaphragm 10 is displaced. Due to this displacement, the volume of the flow path (ink pressurizing chamber) 3 is reduced, the pressure rises, the ink in the flow path 3 is pushed out toward the nozzle 7, and the ink in the vicinity of the nozzle 7 is discharged as droplets. It is ejected from 7.
When the displacement of the vibrating plate 10 is completed and the volume of the flow path 3 returns to the original state, the ink is supplied from the common liquid chamber 2 into the flow path 3. The ink droplets thus ejected from the nozzle 7 adhere to the recording medium 16 (corresponding to claim 2).

3A and 3B are views for explaining another example of the embodiment of the recording head according to the present invention. FIG. 3A is a sectional view in the flow path direction, and FIG. 3B is FIG. It is a top view of the electrostrictive actuator portion of (A), in the figure, 22 is a first electrostrictive actuator, 23 is a second electrostrictive actuator, in the portion that has the same action as in FIGS. Are given the same reference numerals as in FIGS. 1 and 2.

The electrostrictive actuator shown in FIG.
The electrostrictive actuator provided in the upper opening of the flow path 3 shown in FIG. 3, an actuator having a similar configuration, and a structure similar to the electrostrictive actuator, for sealing the upper opening of the fluid resistance portion 4 An electrostrictive actuator is divided by a cell gap 19 and integrally configured, and each has suction ports 18a and 18b for the ferroelectric liquid crystal 11, and is sealed after the ferroelectric liquid crystal 11 is injected. The electrostrictive actuator corresponding to the upper opening of the flow path 3 is a first electrostrictive actuator 22,
The portion corresponding to the upper opening of the fluid resistance portion 4 is called the second electrostrictive actuator 23.

The response speed of the electrostrictive actuator using the ferroelectric liquid crystal 11 is determined by adding the rise time and the fall time, and for the corresponding liquid crystal, 180 to 270 μse.
c. The response speeds of the first electrostrictive actuator 22 that operates on the flow path 3 and the second electrostrictive actuator 23 that operates on the fluid resistance portion 4 are the same because both are manufactured in the same liquid crystal cell. . Therefore, when the first electrostrictive actuator 22 vibrates to cause a change in volume of the flow path 3 and a part of the ink in the flow path 3 becomes an ink droplet and is ejected from the nozzle 7, the common liquid chamber 2 side In the vicinity of the fluid resistance portion 4 of, the negative pressure is generated due to the volume reduction, and the ink is ejected from the nozzle
And try to move in the opposite direction. In order to prevent this phenomenon, it is desirable to completely close the fluid resistance portion 4 when the actuator is actuated, and to create a pressure chamber in which one is closed.

However, this requires the provision of a complicated and expensive mechanism such as a microvalve in the recording head. However, although not perfect, the fluid resistance part 4
The recording head is equipped with a mechanism that makes the conductance of the variable. The fluid resistance is increased at the time of ejection, and the conductance is decreased to reduce the negative pressure (viewed from the nozzle side) in the pressure chamber that occurs at the time of ejection. It is possible to

In the example of the present embodiment shown in FIG. 3, the vibration mechanism is extended based on the intention, and an electrostrictive actuator composed of the ferroelectric liquid crystal 11 is also provided above the fluid resistance portion 4 and the vibration plate 10. The second electrostrictive actuator 23 on the fluid resistance portion 4 is activated prior to the operation of the first electrostrictive actuator 22, the channel (ink pressurizing chamber) 3 is pre-pressurized, and By decreasing the gap value of the flow path 3 formed by the fluid resistance portion 4 and the diaphragm 10, the fluid resistance is increased and the conductance at that portion is decreased.

The first electrostrictive actuator 22, which is operated by delaying the operation of the second electrostrictive actuator 23 by about (1/5) T to (1/4) T (T is the response time of the actuator), It is possible to obtain the ideal ink ejection conditions by benefiting from the applied pressure and the reduced negative pressure generated. As shown in FIG. 3, the first electrostrictive actuator 22 and the second electrostrictive actuator 23 can be manufactured using the same upper and lower substrates, but in order to avoid mutual interference between the actuators,
The inside of the cell is divided into two, so the corresponding inlet is also 1
There are two, 8a and 18b, but only one injection is required,
Moreover, since the relative positions of these two groups of individual electrodes 13a and 13b correspond to the relative positions of the ITO electrodes formed on the same substrate, they can be manufactured by a single photolithography / etching step. Corresponding to).

[0027]

Advantageous Effects of the Invention: A vibrating member provided in at least a part of a flow path forming member constituting a flow path of a recording medium, and a space above the vibrating member and spaced from the vibrating member. Filled in the gap between the first electrode and the second electrode, the first electrode and the second electrode provided on the surfaces of the vibrating member and the substrate that face each other. An electrostrictive actuator which is composed of a dielectric material and is configured to displace the vibrating member by body expansion caused by the dielectric material when a voltage is applied between the first electrode and the second electrode. The electrostrictive actuator is used to displace the vibrating plate to reduce the volume of the flow channel to increase the pressure inside the flow channel, and to give kinetic energy to the recording medium to eject the recording medium. The recording medium is attached to a recording medium for recording. Since the electrostrictive actuator is configured as a part that forms the flow path outside the flow path, not inside the flow path, it becomes possible to bond the electrostrictive actuator to the recording head body after proper alignment. Since there is no direct contact between the ink and the recording medium, it is not necessary to consider the influence of the ink material on the drive generating portion. Therefore, the degree of freedom in selecting the ink material can be obtained.

Effect corresponding to claim 2: The dielectric material is a ferroelectric liquid crystal oriented obliquely with respect to a direction perpendicular to the surfaces of the first electrode and the second electrode, and the electrostrictive material is used. The actuator sandwiches the ferroelectric liquid crystal between the first electrode and the second electrode, seals the ferroelectric liquid crystal cell, and employs a ferroelectric liquid crystal cell as an electrostrictive actuator. It is possible to obtain an actuator drive section that is easy to operate.

Effect corresponding to claim 3: Opposite the first electrostrictive actuator provided in the pressurizing chamber constituted by the variable volume portion in the flow passage, and the recording medium ejecting nozzle in the pressurizing chamber. A second electrostrictive actuator that is provided in the fluid resistance portion on the side and that varies the fluid passage area of the fluid resistance portion to vary the fluid resistance of the fluid resistance portion. Prior to the operation, the second electrostrictive actuator is actuated to increase the fluid resistance of the fluid resistance portion, so that the recording body in the pressure chamber due to the increase in the internal pressure of the pressure chamber moves to the fluid resistance portion side. Since the fluid resistance portion is made to be a variable fluid resistance portion by preventing the fluid from flowing out, the pressure inside the flow path required for ejecting ink droplets and supplying ink to the pressurizing chamber is controlled by the timing of the first electrostrictive actuator. And efficient recording head It is possible to provide. Further, since such a function can be manufactured in the same liquid crystal cell, it can be realized at a minimum cost.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of an embodiment of a recording head according to the present invention.

FIG. 2 is a diagram for explaining a structural example of the embodiment of the electrostrictive actuator according to the present invention.

FIG. 3 is a diagram for explaining another example of the embodiment of the recording head according to the present invention.

FIG. 4 is a partial configuration diagram of a conventional pressure-on-demand multi-head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Bottom plate, 2 ... Common liquid chamber, 3 ... Ink flow path (pressurizing liquid chamber), 4 ... Fluid resistance part, 5 ... Side wall, 6 ... Nozzle plate, 7 ...
Nozzle, 8 ... Ink supply port, 9 ... Electrostrictive actuator,
10 ... Vibration plate, 11 ... Dielectric material, 12 ... Upper substrate, 13 ...
Individual electrodes, 14 ... Common electrode, 15 ... Driving power supply, 16 ... Recording medium, 17 ... Alignment film, 18 ... Encapsulation port, 22 ... First electrostrictive actuator, 23 ... Second electrostrictive actuator,
31 ... Substrate, 32 ... Common liquid chamber, 33 ... Ink pressurizing chamber, 3
4 ... Fluid resistance part, 35 ... Ink supply hole, 36 ... Nozzle plate, 37 ... Nozzle, 38 ... Side wall, 39 ... Vibration plate, 40 ...
Electrostrictive actuator, 41 ... Recording paper.

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055 B41J 2/015

Claims (3)

(57) [Claims] 1. A vibrating member provided in at least a part of a flow path constituting body that constitutes a flow path of a recording medium, and a substrate provided above the vibrating member and facing the vibrating member with a space therebetween. When,
A first electrode and a second electrode provided on the respective surfaces of the vibrating member and the substrate facing each other, and a dielectric material filled in a gap between the first electrode and the second electrode. When a voltage is applied between the first electrode and the second electrode, an electrostrictive actuator using an operation principle that displaces the vibrating member by body expansion caused by the dielectric substance is provided, and the electrostrictive actuator is used. The vibrating plate is displaced to reduce the volume of the flow channel to increase the pressure inside the flow channel, give kinetic energy to the recording medium to eject the recording medium, and attach the recording medium to a recording medium. A recording head characterized by allowing recording. 2. The dielectric material is a ferroelectric liquid crystal that is oriented obliquely with respect to a direction perpendicular to the planes of the first electrode and the second electrode, and the electrostrictive actuator is a ferroelectric liquid crystal. Liquid crystal is sandwiched between the first electrode and the second electrode,
The recording head according to claim 1, wherein the recording head is sealed. 3. A first electrostrictive actuator provided in a pressurizing chamber constituted by a variable volume portion in the flow path, and a fluid resistance portion on the opposite side of the pressurizing chamber from the recording material ejection nozzle. A second electrostrictive actuator that is provided to change the fluid passage area of the fluid resistance portion and to change the fluid resistance of the fluid resistance portion, and prior to the operation of the first electrostrictive actuator, The electrostrictive actuator is operated to increase the fluid resistance of the fluid resistance portion, thereby preventing the recording medium in the pressure chamber from flowing out to the fluid resistance portion side due to the increase in the internal pressure of the pressure chamber. Claim 1 characterized by the above.
Or the recording head according to 2.