JPH01232038A - Electret polymer sheet like article and preparation thereof - Google Patents

Abstract

PURPOSE:To form a polymer sheet having surface high charge density, by provid ing a crosslinked structural film having a specific thickness composed of a silane compound to at least the single surface of a polymer sheet and imparting an electret property to said film. CONSTITUTION:A crosslinked structural film having a thickness of 0.03-0.5mum is formed to at least the single surface of a polymer sheet using a silane com pound or a fluorine compound by plasma polymerization and subsequently treated with a high voltage power supply to prepare an electret polymer sheet like article. As the representative examples of the fluorine compound monomer used in plasma polymerization, there are C2F4, C3F6, C3F8, C4F8 or the like and, as the representative examples of the silane compound, there are trimethoxysilane, trimethoxyvinysilane or the like. An electret degree is pref. 3X10<-10>c/cm<2> or more as surface charge density.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a polymer sheet having a high surface charge density, particularly to a polymer sheet in which the polymer sheet is a polyester film, woven or knitted fabric, or non-woven fabric.

(Conventional technology) Currently, electret products include microphones, headphones,
Applications as electrostatic electroacoustic transducers in hearing aids, loudspeaker telephones, etc. are progressing, but the thinner the electret film is, the higher the surface charge density becomes, making it more effective in utilizing the electrostatic field of the electret. It is. Additionally, electret filters made from non-woven fabrics are attracting attention as a major use for electret ponds, as they can efficiently collect dust. Among these uses, there is also a desire to convert into electret materials that are conventionally difficult to convert into electrets, or those whose performance does not last long even if they are converted into electrets. An example of this is converting polyester into electret.

(Problems to be Solved by the Invention) That is, the problem of the present invention is to convert polymer sheet-like materials such as films, woven or knitted fabrics, and non-woven fabrics into electrets, but especially when the material is polyester, the surface charge density is extremely high. The purpose is to obtain an electret-formed polymer sheet with high (and long-lasting) properties.

(Means for Solving the Problems) That is, the present invention has the following features: [l) A polymer sheet having a film thickness of 0.03 to 0.00 mm (both of which are made of a silane compound or a fluorine compound on one surface).
A polymeric sheet-like material having a crosslinked structure film of 5 μm, the thin film being an electret.

2. A crosslinked structure film is formed on at least one surface of the polymer sheet using a silane compound or a fluorine compound by plasma polymerization, and the film thickness is set to 0.03 to 0.5μ, and then a high voltage DC power source is used to form a crosslinked structure film on at least one surface of the polymer sheet. A method for producing a polymer sheet, which comprises converting the thin film into an electret. ” regarding.

The polymer sheet referred to in the present invention refers to sheet-like materials such as films, woven and knitted fabrics, and nonwoven fabrics. The polymer is not particularly limited, and includes natural polymers, recycled polymers, synthetic polymers, etc. Since polyester, which is generally the most versatile, is difficult to convert into electret and has poor sustainability, the method of the present invention is considered to be particularly effective for polyester.

At least one side in the present invention refers to one or both surfaces of the polymer sheet. A conductive material such as a metal may be attached to the surface of the polymer sheet by coating, vapor deposition, sputtering, ion blasting, etc. for the purpose of an electrode or the like.

The silane compound or fluorine compound monomer used in the present invention will be explained.

The fluorine compound monomers used in the plasma polymerization method are CnHmC&p, which is represented by C,F, C,F,
Ftn-s-p type (a≧0, l≧o, p≧0.2
n-s-p≧1 integer”) , CF, , C, F, , C3
CnHaC12pBrQFgnat- represented by F@
1-P-Q type (n≧1. m≧0, p≧o,
q≧0. 2n+2-s+-'p-q≧1 integer)
, Cn8mC29F*n-m-p represented by C-F3
cyclic type (n≧3, m≧0, p≧012n-m-p
≧l integer), C, F, CnHmC12p
Cyclic type (n
≧4, integer ≧01 gate≧0.2n-2-m-p≧1)
, type represented by C-FsO, NFl, SF, .
There are various types, such as the type represented by IIFg.

Among these, C, F, C3F, C3Fs, C, F, C, F are industrially preferable due to their high film formation speed.
, OlC,)1. F, etc., but C3F, C4Fs are more preferable from the viewpoint of transportation safety, film formation speed, etc.
,C,F,0.

Furthermore, some of these fluorine-based compounds have low film-forming ability when used alone, but when mixed with a small amount of hydrogen gas or non-polymerizable gas and subjected to plasma polymerization, the film-forming rate can be significantly improved. CF, , C4s, C,F, , CtH-F can significantly improve the film formation rate when mixed with hydrogen gas.
* is typical, and C, F, , C, F, , C4F, , C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,, C, F,
C5F-0 etc. are representative.

Among the non-polymerizable gases, inert gases are most effective, and argon gas is particularly effective. The fluorine-based compound may contain atoms such as hydrogen, chlorine, and bromine.

In addition, the silicon thread compound mo/mer used in the present invention is p.

Kri CH,, C mountain, CL=CH, H%Q.

an alkoxysilane-based silicon compound represented by any of the following), a chlorosilane-based compound represented by any of the following (30, -cI2, Cl2CH*), where R is an alkyl group, and X is either OCH3 or 0CtHs) A silane coupling silicon compound represented by (where R1-R1 is H, CH3, CtHs, 5i(CHt
) *, any) (where R is a 7/l/kill group, and X is CQ, NHt).Reactive siloxane oligomer silicon compounds that are Methoxysilane, trimethoxyvinylsilane, triethoxysilane, triethoxyvinylsilane, trimethoxychlorosilane, trimethylmethoxysilane, ~dimethoxyvinylsilane, dimethylmethoxyvinylsilane, trimethylvinylsilane, triethylvinylsilane, vinyltrifluorosilane, hexamethyldisilazane, dimethyltrimethylsilylamine , aminosiloxane, chlorosiloxane, etc.

When a silicon compound is supplied into a plasma device, it may be mixed with an inert gas such as argon nitrogen as a carrier gas, or may be mixed with oxygen or the like in order to form a more dense film.

Plasma polymerization in the present invention refers to a polymerization method using low-temperature plasma discharge, and refers to a method of forming a polymer film while supplying one or more polymerization monomers during discharge.

Low-temperature plasma is a plasma generated during discharge that is characterized by an average electron energy of 10 eV (lo'~lO'K) and an electron density of 1 G''~1 G''am-', and at the same time, the plasma generated during discharge is characterized by a change in electron temperature and gas temperature. It is also called non-equilibrium plasma because no equilibrium is established between the two.

There are no particular restrictions on the apparatus for plasma polymerization (it may be a continuous type, a batch type, an internal electrode type, or an external 74-electrode type).

Normally, the degree of vacuum during discharge is kept at about O, O1 = 0.5 Torr, and the output is O,1w/c+i''~5w/aI11
"Processing time is generally several seconds to several minutes,
It is desirable that the film thickness is about 0.03 to 0.05 μm. If the film thickness is less than 0.03μ, the electret effect will be small;
If the film thickness exceeds 0.5μ, the film itself tends to become hard and brittle, which is not desirable.

To measure the film thickness, place a cover glass on a slide glass and place it on the electrode set with the sample in the plasma processing device. After plasma and polymerization, remove the cover glass and examine the steps created on the slide glass using an interference microscope. Measure.

Electretization is the process of converting a plasma thin film into an electret. When plasma thin films exist on both sides of a polymer sheet, both sides can be made into electrets with the same polarity or with different polarities (and even with negative polarity). Alternatively, if a plasma thin film exists only on one surface of the polymer sheet, that thin film may be made into an electret.

An ordinary device may be used for electretization.

That is, it is carried out using a DC power source that generates a high voltage of several tens of kilovolts, a strip device that includes a rolled electrode (suitably grounded) with which the sample comes into contact, and a counter electrode (needle electrode).

In order to increase the efficiency of electretization, it is preferable that the roll be heated. Alternatively, as a simple type, a device that performs corona discharge may be used.

The degree of electret depends on the processed material, voltage, processing speed,
The distance between the electrodes can be arbitrarily selected depending on the roll temperature, but care must be taken since applying too high a voltage may cause the sheet to tear or melt. The degree of electretization is preferably 1X10''10c/cl! or more as a surface charge density, preferably 3X1G-10c/c+a'.

The surface charge density was measured by the method shown in FIG. Place the sample 1 on the grounded metal plate 2, and place it on the other metal electrode plate (
(4 cm diameter) 3 is brought into contact with the sample 1 from above to induce sample charge to the metal electrode plate 3, which is stored in a known capacitor 4, and the potential of the capacitor 4 is measured with an electrometer 5.

Surface charge density (c/am') = Cx V x SC
: Capacitance of capacitor (Farad) ■ = Voltage (Volt) S: Surface of metal electrode plate (am'') The following will be explained according to Examples.

Example 1 Both sides of a biaxially stretched film (thickness lOμ) made of polyethylene terephthalate were coated with C, F, and monomers at a flow rate of 30 CC/min and a vacuum level of 6.3 Torr and an output of 0.177)/ca.
+” for 120 seconds, and the film thickness was O,
A crosslinked thin film of tSμ was formed.

High frequency power source: 13.56 MHz Electrode: Parallel plate electrode One side of this sheet was given a charge of 2 by a 50 KV DC power source.

Electrode opening l1ll 5cm Electrode temperature on the side in contact with the sheet 12 G 'C Processing time 5 seconds Applied voltage 30KV Next, turn the film over and adjust the power supply part in the same way so that it has one charge and convert it into an electret. did.

As a comparative example, a polyethylene terephthalate film that had not been subjected to plasma polymerization treatment was similarly made into an electret on both sides.

The surface charge density of a film with plasma polymerized thin film is @
7X 10-@c/c+*', (96,5X 10-
"c/co+", and the surface charge density of the film not subjected to plasma polymerization treatment is e5x 10-"c/am",
θ4X 10-"c/c11".

In order to investigate the retention of electretization of the plasma polymerized thin film, the surface charge density was measured after it was placed in a 10 G'C atmosphere for 100 hours.
c/cm", e 6.4X 10-"c/cm", maintaining the initial performance.

Example 2 A high-density tuck fabric was woven using drawn yarns made of 50 denier 96 filaments of polyethylene terephthalate as warp yarns and coco yarns. The fabric was subjected to the conventional steps of desizing-scouring-presetting (TGO°C for 1 minute)-dying-finishing.

A plasma polymerized thin film was applied to one surface of this fabric using vinyltrimethoxysilane monomer.

The same plasma polymerization conditions and equipment as in Example 1 were used. The film thickness at this time was 0.12μ.

This fabric was made into an electret under the same conditions as in Example 1. Electretization refers to only the plasma polymerized surface.
It was given a charge of ■.

Dustproof clothing was made using this fabric. The clothes were made so that the electret side was on the outside (the side that was not attached to the body). As a control, electret dustproof clothing was similarly prepared using a fabric that had not been subjected to plasma polymerization treatment.
-We investigated the amount of dust emitted from the body when working at a desk for an hour wearing these clothes, compared to when doing it naked. The amount of rash produced when working at a desk naked is 100, and when wearing clothes made of plasma polymerized electret, it is 2.0 when wearing clothes made of electret treated by plasma polymerization. We were able to suppress the amount of dust generated.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for measuring surface charge density. Patent applicant: Rira Co., Ltd. Agent: Ken Honda, patent attorney

Claims (1)

[Claims] 1. A film made of a silane compound or a fluorine compound on at least one surface of the polymer sheet with a thickness of 0.03 to 0.5
1. A polymer sheet-like material having a crosslinked structure film of μ, the thin film being an electret. 2. A crosslinked structure film is formed on at least one surface of the polymer sheet using a silane compound or a fluorine compound by plasma polymerization, and the film thickness is set to 0.03 to 0.5μ, and then a high voltage DC power source is used to form a crosslinked structure film on at least one surface of the polymer sheet. A method for producing a polymer sheet, which comprises converting the thin film into an electret.