JPH03151251A - Laminate type piezoelectric element - Google Patents

Abstract

PURPOSE:To obtain a high electric insulation property combined with a moisture-proof property by a method wherein exterior surface of inner electrodes and outer electrodes is covered with two or more electric insulation layers which have different characteristics and are laid upon another. CONSTITUTION:A laminate type piezoelectric element 10 consists of piezoelectric materials 1... which are laminated in two or more layers, thin membrane inner electrodes 2... which are sandwiched between the piezoelectric materials 1..., and outer electrodes 3 which are arranged along the side walls of the piezoelectric materials 1... in order to connect the inner electrodes 2... to a power source, and the whole external surface of the laminated piezoelectric element is covered with an electric insulation coating film 4. The electric insulating coating film 4 consists of two or more electric insulating layers 4a and 4b having different characteristics, and is applied on the external surface of the inner electrodes 2... and the outer electrodes 3. The electric insulating layers 4a having high electric insulating property maintain the basic electric insulation property, and the electric insulation layers 4b having an excellent water-proof property maintain the electric insulation property in a high humidity atmosphere. As a result, a basic electric insulating property and an excellent moisture- proof property can be obtained.

Description

[Detailed Description of the Invention] [Summary] Regarding a laminated piezoelectric element used to drive an impact dot wire of an impact dot printer, etc., a laminated piezoelectric element capable of obtaining high electrical insulation properties including moisture resistance. 12, a piezoelectric material laminated in multiple layers, a thin film-like internal electrode inserted between each layer of the laminated piezoelectric material, and each internal electrode as a power source. A multilayer piezoelectric element having an external electrode disposed along a sidewall of the piezoelectric material for connection,
It is constructed by overlapping a plurality of electrically insulating layers with different properties to coat the surfaces of the alignment part electrode and the external electrode.

[Industrial application field]

The present invention relates to a laminated piezoelectric element used to drive an impact dot wire or the like of an impact dot printer.

Impact dot wires (hereinafter simply referred to as "wires") in impact dot printers are generally driven using electromagnetic force, but recently, piezoelectric wires that create distortion by applying an electric field have been introduced. Devices in which one ear is driven by a laminated piezoelectric element in which elements are laminated are also often used.

In such a laminated piezoelectric element, a high η pressure is applied between electrodes that are arranged at very narrow intervals with the piezoelectric element in between, so a slight insulation failure can unexpectedly cause malfunction. Therefore, ensuring electrical insulation for laminated piezoelectric elements has become a very important issue.

[Conventional technology]

In the conventional laminated piezoelectric element, as shown in FIG. Piezoelectric material to connect to the power source 5! An external electrode 53 is disposed along the side wall of the piezoelectric element, and an electrically insulating layer 54 made of an epoxy or polymeric material is coated on the surface of the piezoelectric element for insulation.

[Problem to be solved by the invention]

However, when coating the electrically insulating N54 on the surface of the electrodes 52 and 53, fine particles may be formed in the coated electrically insulating layer 54 due to air being entrained during coating and the diluent contained in the coating material evaporating. bubble 5
1 and holes 52 are often present.

If bubbles or holes are present in the electrical insulating layer as described above, the electrical insulation properties will be lowered, and in particular, leakage will easily occur due to dew condensation or the like. Therefore, insulation failure is likely to occur in a high humidity environment, resulting in malfunctions.

An object of the present invention is to provide a laminated piezoelectric element that can eliminate such conventional drawbacks and obtain high electrical insulation properties including moisture resistance.

[Means to solve the problem]

In order to achieve the above object, the laminated piezoelectric element of the present invention includes a piezoelectric material 1 laminated in a plurality of layers, and a piezoelectric material 1 laminated in a plurality of layers, as shown in FIG. The thin film internal electrodes 2 inserted between the layers of the piezoelectric materials 1 and the piezoelectric materials 1 are used to connect the internal electrodes 2 to a power source. In a laminated piezoelectric element having an external electrode 3 disposed along the side wall of the
It is characterized in that the surfaces of the internal electrodes 2 and external electrodes 3 are coated by overlapping a plurality of electrically insulating layers 4a and 4b with different characteristics.

[Effect]

Electrical insulation F covering the surfaces of internal electrodes 2... and external electrodes 3
By combining J4a and 4b with different characteristics, such as using a material with high insulation (voltage resistance) for the - layer and a material with low water absorption for the - layer, high electrical insulation and high moisture resistance can be achieved. Can be combined.

Furthermore, since a plurality of electrically insulating layers 4a and 4b are overlapped, even if there are bubbles or holes in each electrically insulating layer 4a or 4b, the positions of the bubbles or holes are shifted from layer to layer, and the outer surface and the electrode surface are directly connected. The possibility of communication is significantly reduced.

〔Example〕

Examples will be described with reference to the drawings.

*2 Figure shows the appearance of the laminated piezoelectric element IO. The piezoelectric material l... is, for example, a thin plate made of piezoelectric ceramic with a thickness of about 0.1 mm, and about 20 pieces of the same shape are laminated. And between each piezoelectric material l..., a thin film-like internal electrode 2... with a thickness of about 5 μm, for example.
is sandwiched between sandwich wipes. Internal electrode 2...
* is formed of silver foil, for example.

The internal electrodes 2... are formed in the same shape as the piezoelectric materials l...- except for the thickness, and when a voltage is applied between the two internal electrodes 2... that sandwich each piezoelectric material l... Well, the piezoelectric material in between! Distortion (deformation) occurs in...

Reference numeral 3.3 denotes a pair of external electrodes that connect every other internal electrode 2, and are made of, for example, silver foil.

A pair of external electrodes 3.3 are fixed along the side walls of the piezoelectric material 1 at 180 degree symmetrical positions. and,
One external layer S3 connects the odd-numbered internal electrodes 2 as one group, and the other external electrode 3 connects the even-numbered internal electrodes 2 as one group. .

5... is an internal electrode that must not be connected! It is an insulating sealing material made of glass that insulates and seals every other surface of each internal electrode l... in order to insulate between the group and the external electrodes 3.3.

6.6 are electric wires connected to different external electrodes 3, 3, respectively. The electric wires 6.6 are connected to a power source (not shown) via a drive circuit controlled by the print signal, and a voltage of, for example, about 120 volts is applied from the electric wires 6.6 to the external electrodes 3, 3. It is applied to the internal electrodes 2... As a result, each piezoelectric material 1... is distorted, and the wJrIs type piezoelectric element IO as a whole expands and contracts in the stacking direction.

In the laminated piezoelectric element 10 of the present invention, the outer surface of the side wall of such a laminated structure is entirely coated with an electrically insulating layer 4. However, the illustration thereof is omitted in FIG. 2, and the electrical insulating layer 4 will be described later with reference to FIG.

FIG. 3 schematically shows how the laminated piezoelectric element 1O is used, and is used in a print head of an impact dot printer. Only one end side 10a of the laminated piezoelectric element IO is fixed to the print head, and a wire is connected to the other end side lOb via a connecting member (beam) 12! 3 are connected. Therefore, the wire 13 is driven by applying a voltage to the internal electrodes 2 through the electric wire 6 and causing the laminated piezoelectric element 10 to expand and contract.

FIG. 1 shows a cross section of the electrically insulating layer 4 described above.

The electrically insulating layer 4 is formed by overlapping and coating a plurality of electrically insulating layers 4a and 4b with different characteristics on their outer surfaces so that the internal electrodes 2 and external electrodes 3 are not exposed, thereby forming a multi-rfI electrically insulating layer. It was formed.

In the embodiment shown in FIG. 1, the inner two layers 4a are flexible electrical insulating layers with excellent adhesion to one electrode and high electrical insulating properties (voltage resistance), such as silicon resin electrical insulating layers. material is used.

On the other hand, the outer two layers 4b are electrical insulating layers with low water absorption and excellent waterproof properties, and are made of, for example, silicone grease.

By forming the electrical insulating layer 4 in such a combination, one electrical insulating layer 4a with high withstand voltage can ensure basic electrical insulation, and the other electrical insulating layer 4b with excellent waterproofness can withstand high humidity. Electrical insulation is ensured in this environment.

However, the electrical insulating layer 4 is not limited to such a combination, and can be made of various combinations of organic, inorganic, composite materials, etc., such as using a highly rigid epoxy board.

The thickness of each electrically insulating layer 4a, 4b is preferably approximately 10 μm or less in order to facilitate the removal of air bubbles from within the layer, and defoaming treatment may be performed when coating each layer to remove air bubbles.

In the present invention, the electrical insulating layer 4 is formed of at least two electrical insulating layers having different characteristics.
1# (By coating the 17M neo material on top of the above-mentioned floating shelf 1 in multiple layers, conduction between the outer surface and the electrode due to bubbles or holes can be more completely prevented. Can be done.

Further, if the electrode is subjected to a nonconductor treatment before being coated with an electrically insulating layer, the insulation performance will be further improved.

When using a silver electrode, silver sulfide, which is a nonconductor, can be generated on the surface of the electrode by passing it through an atmosphere of hydrogen sulfide.

〔Effect of the invention〕

According to the laminated piezoelectric element of the present invention, the surface of the electrode is coated by stacking multiple electrically insulating layers, so even if there are bubbles or holes in the electrically insulating layer, the outer surface and the electrode surface will not communicate with each other. Moreover, since the electrical insulation layer is coated with multiple electrical insulation layers with different properties, by selecting and combining their properties, it is possible to achieve both basic high insulation properties and excellent moisture resistance. It has excellent effects such as being able to operate stably without leaking even in a humid environment, and also having excellent mechanical strength.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged sectional view of the embodiment. Figure 2 is an external perspective view of the embodiment; Figure 3 is a side view of the example in use; FIG. 4 is a partially enlarged sectional view of a conventional example. In the figure, 1... piezoelectric material, 2.-internal electrode, 3...external electrode, 4... Electrical insulation layer. Figure 4

Claims (1)

[Scope of Claims] Piezoelectric materials (1...) laminated in a plurality of layers, and thin film-like internal electrodes (2...) sandwiched between each layer of the laminated piezoelectric materials (1...).・) and each of the above internal electrodes (2
The above piezoelectric material (1...) is used to connect the piezoelectric material (1...) to a power source.
In a laminated piezoelectric element having an external electrode (3) arranged along the side wall of the internal electrode (2... ) and an external electrode (3) are coated on the surface thereof.