JPS5953715B2 - Manufacturing method of flexible piezoelectric sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a flexible piezoelectric sheet used as a vibrating membrane for speakers, microphones, headphones, etc. It is an object of the present invention to provide a method for manufacturing a flexible piezoelectric sheet that is excellent in terms of performance.

When manufacturing this type of piezoelectric sheet, for example, by the doctor blade method, conventionally, on a Mylar sheet,
The mixture filled in the tank (ferromagnetic powder dispersed in synthetic rubber or thermoplastic resin) is stretched and applied to a predetermined thickness using a doctor knife, and after drying, the mixture sheet is peeled off from the Mylar sheet. After that, the piezoelectric sheet was cut into a predetermined size, electrodes were formed on both sides, and polarization was performed to obtain a piezoelectric sheet.

Piezoelectric sheets formed in this way have low mechanical strength against tension, etc., so they must be handled with care, and even when used as a vibrating membrane for speakers, etc., they are not suitable for use in areas with large vibrations and high amplitudes. However, the practical range was narrow, and the use of expensive mylar sheets inevitably led to a rise in manufacturing costs.

The present invention solves the above-mentioned conventional drawbacks by using an organic fiber cloth sheet such as polyester and embedding it in a mixture.

The present invention will be described below with reference to drawings and examples. In the drawing, 1 is an endless belt that is wound around drive rolls 2, 2 so that it can run freely in the direction of the arrow. Silicone rubber with good releasability is preferably used, but even metal belts may have chrome plating or Teflon coating on their surface. It can be used if it is processed as follows. Reference numeral 3 denotes a tank installed above the feeding side of the endless belt 1, which stores a slurry-like mixture 4, and has a lower end of its side wall as a doctor knife 5 forming a predetermined gap between it and the belt 1.

The slurry-like mixture 4 has a matrix of synthetic rubber such as chloroprene rubber or fluororubber, or a thermoplastic resin such as polyvinyl fluoride or polyvinylidene fluoride, and an appropriate amount of ferromagnetic powder such as lead zirconate titanate. For example, 100 to 100 parts by weight of the matrix
2000 parts by weight were mixed together and thoroughly kneaded together with a solvent and the like. 6 is a drying chamber installed on the delivery side of the endless belt 1, and 7 is a carrier sheet placed on the upper surface of the endless belt 1, which is made of organic fiber cloth such as polyethylene, nylon, vinylon, etc.

Note that 8 is an upper and lower roll that supplies the fiber cloth sheet 7 to the feeding side of the endless belt 1, and 9 is a roll that winds up the sheet led out from the doctor knife 5 through the drying chamber 6. As the endless belt 1 moves in the direction of the arrow, the organic fiber cloth sheet 7 placed on the belt also moves in the same direction, and while passing the bottom surface of the tank 3, part of the slurry mixture 4 in the tank is impregnated and applied, formed to a constant thickness with a doctor knife 5, and guided out.

The sheets t derived from this doctor knife 5 are the second and third sheets.
As shown in the figure, a portion 4a of the mixture passes from the surface layer of the organic fiber cloth sheet 7a to the back layer portion of the organic fiber cloth sheet 7a through countless meshes, and the entire cloth sheet 7 is buried therein. The fabric sheet t drawn out from the doctor knife 5 is sent to a drying chamber 6, where it is thoroughly dried by volatilizing the solvent contained in the mixture, and then peeled off from an endless belt and wound up by a roll 9. It will be done. In this case, since the endless belt is made of silicone rubber or surface-treated metal, the sheet t is easily peeled off from the belt 1. The sheet t thus obtained is cut into predetermined external dimensions,
Electrode layers are formed on both sides by aluminum evaporation or the like, and a DC electric field is applied between the electrode layers to perform polarization treatment.

Incidentally, a mixture of 100 parts by weight of chloroprene rubber, 950 parts by weight of lead zirconate titanate, and appropriate amounts of a vulcanizing agent and a solvent was used, and a fiber cloth sheet with a thickness of 0.1 μm and a mesh size of 60 mm was used. The piezoelectric sheet manufactured using mesh polyester fiber cloth according to the above example exhibited a piezoelectric constant D3l of 30 x 10-12 m/V, and also showed high mechanical strength without breaking at all even in a manual tearing test. It exhibited strength.

As described above, according to the manufacturing method of the present invention, the carrier sheet made of organic fiber cloth with excellent toughness is directly embedded in the piezoelectric mixture, so it has high mechanical strength, is easy to handle, and has a large capacity. It is possible to provide a flexible piezoelectric sheet that can sufficiently withstand even when used under high vibration amplitude,
Moreover, since the carrier sheet uses organic fibers that are cheaper than conventional mylar sheets, it brings about benefits such as a significant reduction in manufacturing costs.

Although the present invention has so far been explained with reference to the doctor blade method, it is also applicable to other forming methods that are widely known as continuous forming methods for various sheets using a carrier sheet, such as the roll coater method and the dipping method. It can be applied.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of a doctor blade device exemplified to explain the method of manufacturing a flexible piezoelectric sheet of the present invention.

Claims (1)

[Claims] 1. A mixture of ferromagnetic powder dispersed in synthetic rubber or thermoplastic resin is applied onto a carrier sheet made of organic fiber cloth using a doctor blade method or the like, and after drying,
A method for producing a flexible piezoelectric sheet characterized by polarization.