JP2000198195A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cope with high densification and an increase in the number of nozzles and to simply assemble in a high density by covering a plurality of regions sandwiched between positive electrodes and negative electrodes of a plurality of pressure generating elements with insulating elastic materials. SOLUTION: A plurality of pressure generating elements 11 are provided on a board 12. Negative electrodes 17 and positive electrodes 18 are constituted on sides and bottoms of the elements 11 to apply a voltage to intersected electrodes of the elements 11 by fixing the elements 11 by an adhesive layer 19. The sides of the elements 11 perpendicular to its pressure generating surfaces 11a are covered with insulating low elastic materials 13 having low elastic modulus. An insulating high elastic material 14 having a high elastic modulus is formed in a protruding state on the surfaces 11a, and spacers 20 are constituted at a suitable interval between the board 12 and a nozzle forming board 15 having a plurality of nozzle openings 16.

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 apparatus such as a printer which forms an ink image on a recording medium such as recording paper by flying ink droplets, and more particularly to an ink jet head.

[0002]

2. Description of the Related Art A nozzle forming substrate having a plurality of nozzles, a pressure generating element made of a piezoelectric material and a conductive material disposed opposite to the nozzle, a gap between the pressure generating element and the nozzle forming substrate, Japanese Patent Publication No. Sho 60-8953 discloses an on-demand type ink jet head which includes an ink which fills the periphery of a pressure generating element and which displaces the pressure generating element by an applied voltage to discharge ink from a nozzle.

Further, as a conventional technique, a plurality of ink cavities are formed between a glass substrate and a glass thin plate, and a plate of a pressure generating element having electrodes formed on both sides is cut into a size of about the area of the ink cavities. There is an ink jet head in which a thin glass plate is sandwiched over the ink cavity.

In such a print head, it is desirable that the droplet formation efficiency and the flying force be large. However, since the unit length of the pressure generating element and the expansion / contraction ratio per unit voltage are extremely small, a high printing voltage is required in order to obtain the flying force required for printing, and the driving circuit and insulation measures are complicated. There is a problem that.

In order to solve such a problem, Japanese Patent Application Laid-Open
As described in Japanese Patent Publication No. 295269, a pressure generating element for an ink jet print head in which a piezoelectric material and a conductive material are alternately laminated has been proposed. According to this pressure generating element, the distance between the electrodes can be made extremely small, so that the voltage of the drive signal can be reduced.

[0006]

However, by using a pressure generating element obtained by laminating and firing a piezoelectric material and a conductive material, an interval for storing ink is formed between a nozzle opening and a free end of the pressure generating element. In the on-demand type ink jet head, since the piezoelectric material is formed to be extremely thin, the electric field intensity is extremely large, and there is a concern that the dielectric breakdown between the electrodes or the ink may occur.

In the prior art, since the width of the ink cavity is about several hundred μm on one side, a plurality of plates obtained by cutting the pressure generating element into the size of the ink cavity are used for each ink cavity. Must be adhered to. For this reason, the variation in characteristics due to the non-uniformity of the adhesion is large, peeling of the bonded portion is likely to occur, the alignment accuracy between the ink cavity and the plate of the piezoelectric body cannot be increased, internal distortion occurs during cutting of the piezoelectric body, There has been a problem that characteristics are likely to vary, and the number of constituent members is increased, resulting in poor productivity.

[0008] These problems become more pronounced as the number of nozzles is increased or as the density of the nozzles is increased.

Therefore, the present invention solves such a problem, and its object is to cope with high density and a high number of nozzles and to enable high-density and simple assembly.
An object of the present invention is to provide an inkjet head having high operation efficiency and excellent durability.

[0010]

According to the present invention, there is provided an ink jet head comprising: a nozzle forming substrate provided with a plurality of nozzles for discharging ink; and one end near one end for applying pressure to the ink, the substrate being fixed to the substrate. The ends are a plurality of pressure generating elements which are stacked vertical vibrators acting as pressure generating surfaces,
A voltage applying means for applying a voltage for generating pressure to the pressure generating element, a substrate for fixing the pressure generating element, and a member for receiving vibration of the pressure generating element; A plurality of regions sandwiched by both the electrode and the negative electrode are covered with an insulating elastic material.

[0011] Further, the invention is characterized in that the insulating elastic material covers from a member receiving the vibration of the pressure generating element to an adhesive layer provided on the substrate for fixing the pressure generating element.

Further, the member receiving vibration of the pressure generating element is an insulating elastic material, and has a different elastic modulus from that of the insulating elastic material covering the pressure generating element.

Further, the elastic modulus of the insulating elastic material of the member receiving the vibration of the pressure generating element is higher than the elastic modulus of the insulating elastic material covering the pressure generating element.

A member made of an insulating elastic material is provided on the pressure generating surface side of the pressure generating element, and a member made of the insulating elastic material is provided on the pressure generating surface side of the pressure generating element. Is formed in a convex shape with respect to.

Further, a member made of an insulating elastic material has a concave portion on a surface facing the nozzle opening on the pressure generating surface side of the pressure generating element.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view of a main part of an ink jet head showing a first embodiment of the present invention, and FIG. 2 is a top view (a) of the main part of the ink jet head and a sectional view (A) of FIG. It is.

As shown in these figures, the pressure generating element 11 provided on the substrate 12 is fixed by an adhesive layer 19.
On the side surface perpendicular to the pressure generating surface 11a of the pressure generating element 11, an insulating and low elastic material 13 having a low elastic modulus has a thickness of 100 mm.
It is coated to about 200 μm.

On the pressure generating surface 11a, a high elastic insulating material 14 having a relatively high elastic modulus is formed in a convex shape.

A spacer 20 is provided between the substrate 12 and the nozzle forming substrate 15 having a plurality of nozzle openings 16 so as to maintain an appropriate space therebetween.

Further, in order to apply a voltage to the interdigital electrodes of the pressure generating element 11, a negative electrode 17 and a positive electrode 18 are formed on the side and bottom of the pressure generating element 11.

FIG. 3 is a perspective view of a main part of an ink jet head showing a second embodiment according to the present invention, and FIG. 4 is a top view (a) of the main part of the ink jet head and a sectional view (A) of FIG. It is.

As shown in these figures, the pressure generating element 11 provided on the substrate 12 is fixed by an adhesive layer 19.
On the side surface perpendicular to the pressure generating surface of the pressure generating element, an insulating low-elastic material 13 having a low elastic modulus has a thickness of 100 to 200 μm.
m.

On the pressure generating surface 11a, an insulating high elasticity material 14 having a relatively high elastic modulus is formed in a convex shape.
Further, the pressure generating surface 14a facing the nozzle opening 16
Is formed to have a concave cross-sectional shape. Substrate 1
A spacer 20 is provided between the nozzle forming substrate 15 having two nozzles and a plurality of nozzles so as to maintain an appropriate space therebetween.

In order to apply a voltage to the interdigital electrodes of the pressure generating element 11, a negative electrode 17 and a positive electrode 18 are formed on the side and bottom of the pressure generating element 11.

FIG. 5 is a perspective view of a serial printer equipped with an ink jet head according to the present invention. 1 is an ink jet head of the present invention, and 2 is its carriage. 3 is a carriage drive shaft, and 4 is a carriage guide. The recording paper 8 wound on the platen is pressed by a paper feed roller 7 and a paper holder 6.
As the paper feed roller 7 rotates, the recording paper 8 is fed in the direction of arrow A in the figure. At this time, the inkjet head 1 forms an ink image on the surface of the recording paper 8 while moving in the direction of arrow B in the figure.

Generally, the displacement δ of the pressure generating element is proportional to the length L and the electric field strength E as shown in the equation (1).

[0028]

(Equation 1)

Further, as shown in the equation (2), the generated force f
Also has a characteristic that it is proportional to the electric field strength E.

[0030]

(Equation 2)

FIGS. 7A and 7B show the structure of an ink jet head using a conventional pressure generating element 11. FIG.

Conventionally, the pressure generating member 23 is constituted by a thick single-layer piezoelectric material 21 and an elastic plate 22. In such a structure, unless the applied voltage is increased in order to increase the electric field strength E, sufficient displacement and generated force cannot be obtained, and the cost of the drive circuit has to be increased. However, by using a laminated type pressure generating element 11 in which a thin layer of the piezoelectric material 21 such as the pressure generating element 11 shown in FIG. Power can be realized.

Incidentally, as in the present embodiment, the piezoelectric material 2
By setting the thickness of the first layer to about several tens of μm, it is possible to drive at a low voltage of about 24 V, and the production cost and running cost can be extremely reduced.

[0034]

According to the present invention, in order to effectively use a laminated pressure generating element having an extremely high electric field strength, a plurality of regions sandwiched by both the positive electrode and the negative electrode of the pressure generating element are made of an insulating elastic material. Characterized by being coated with By performing such a process, it is possible to realize an ink jet head that suppresses dielectric breakdown of the pressure generating element, suppresses driving noise generated when the pressure generating element is driven, and suppresses residual vibration.

Further, the elastic modulus of the insulating elastic material is changed according to the displacement direction and the area of the pressure generating element. This makes it possible to perform the above-described processing effectively without sacrificing the displacement efficiency.

Further, a member made of an insulating elastic material is provided on the pressure generating surface side of the pressure generating element, and a member made of the insulating elastic material is provided on the pressure generating surface side of the pressure generating element. Is formed in a convex shape with respect to
In addition, since the member made of an insulating elastic material has a concave portion on the surface facing the nozzle opening on the pressure generating surface side of the pressure generating element, stable supply and stable ejection of ink can be realized.

[0037]

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of an inkjet head according to a first embodiment of the present invention.

FIGS. 2A and 2B are a top view and a cross-sectional view taken along the line AA of a main part of an inkjet head according to a first embodiment of the present invention.

FIG. 3 is a perspective view of a main part of an inkjet head according to a second embodiment of the present invention.

FIGS. 4A and 4B are a top view and a cross-sectional view taken along line AA of a main part of an inkjet head according to a second embodiment of the present invention.

FIG. 5 is a perspective view of a serial printer equipped with an inkjet head according to the present invention.

FIG. 6 is a structural view of an ink jet head using a stacked pressure generating element according to the present invention.

FIGS. 7A and 7B are structural diagrams of an inkjet head having a cantilever structure, and an inkjet head in which a pressure generating member is attached to a thin glass plate.

[Explanation of symbols]

 Reference Signs List 1 inkjet head 2 carriage 3 carriage drive shaft 4 carriage guide 5 platen 6 paper press shaft 7 paper feed shaft 8 recording paper 11 pressure generating element 11a pressure generating surface 12 substrate 13 insulating low elastic material 14 insulating high elastic material 14a pressure generating surface 15 Nozzle forming substrate 16 Nozzle opening 17 Negative electrode 18 Positive electrode 19 Adhesive layer 20 Spacer

Claims (6)

[Claims] 1. A nozzle forming substrate having a plurality of nozzles for discharging ink, and a nozzle for applying pressure to the ink.
A plurality of pressure generating elements, each of which is a stacked vertical vibrator, having one end near the substrate and the other end acting as a pressure generating surface, and a voltage application for applying a voltage for generating a pressure to the pressure generating element. Means, a substrate for fixing the pressure generating element, and a member that receives vibration of the pressure generating element,
An ink jet head, wherein a plurality of regions sandwiched by both a positive electrode and a negative electrode of the pressure generating element are covered with an insulating elastic material. 2. The semiconductor device according to claim 1, wherein a portion from a member receiving the vibration of the pressure generating element to an adhesive layer for fixing the pressure generating element provided on the substrate is covered with the insulating elastic material. 2. The inkjet head according to item 1. 3. The pressure receiving element according to claim 1, wherein the member receiving the vibration is an insulating elastic material, and has a different elastic modulus from the insulating elastic material covering the pressure generating element. Inkjet head. 4. The elastic modulus of the insulating elastic material of the member receiving vibration of the pressure generating element is higher than the elastic modulus of the insulating elastic material covering the pressure generating element.
The inkjet head according to any one of claims 1 to 3. 5. A member made of an insulating elastic material is provided on the pressure generating surface side of the pressure generating element, and a member made of the insulating elastic material is provided on the pressure generating surface side of the pressure generating element. The inkjet head according to any one of claims 1 to 4, wherein the inkjet head is formed to have a convex shape. 6. The pressure generating element according to claim 1, wherein a member made of an insulating elastic material has a concave portion on a surface facing the nozzle opening on a pressure generating surface side of the pressure generating element. Item 7. The inkjet head according to item 1.