JPS63213563A - High polymer composite dielectric - Google Patents

Abstract

PURPOSE:To obtain a high polymer composite dielectric, having no piezoelectric characteristic and high dielectric constant, by blending a calcium-substituted titanate, prepared by an oxalate precipitation method and having a specific amount of calcium substituent groups with a rubber-like high polymer and/or resinous high polymer. CONSTITUTION:A high polymer composite dielectric obtained by blending 1-200 pts.wt. fine powder of ferroelectric oxide, prepared by adding an oxalate dissolved in one kind of alcohol selected from the group consisting of ethanol and propanol to an acidic aqueous solution containing lead, calcium and titanium so as to provide oxalic acid in the total amount of 0.98-1.02mol. based on 1mol. Pb and 1mol. Ca and 0.49-0.51mol. based on based on 1mol. Ti, neutralizing the acid in the resultant aqueous solution containing a precipitate composition with an amine or ammonia, then separating the obtained precipitates, washing the precipitates and firing the washed precipitates at 600-1,200 deg.C and expressed by the formula (0.35<=x<0.95) with 10pts.wt. rubber-like and/or resinous high polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION Background of the Invention (Technical Field and Problems) The present invention relates to a polymer composite dielectric material having a large dielectric constant.

Resin-like polymer films have traditionally been used as dielectric materials for capacitors and other devices. It is used by winding or laminating films stretched to a thickness of several micrometers. These capacitors have superior characteristics compared to aluminum electrolytic capacitors, ceramic cosidensors, etc., but the dielectric constant of the polymer film is PVDF (polyvinylidene silica).
However, it is difficult to obtain a small capacitor with a large capacitance because it does not exceed 15. To solve this problem, the dielectric constant is increased by compounding ceramic particles with a large dielectric constant into a polymer film. Efforts have been made. For example, JP-A-60-18
In Publication No. 5303, barium titanate is heated to nearly 900°C, then poured into water and rapidly cooled to finely pulverize it, mixed with PVDF and triallyl isocyanurate as a crosslinking aid, and subjected to radiation crosslinking and then stretching. The aim is to make the film thinner and improve the dielectric constant at the same time. However, even with this technique, it has not been possible to produce a thin film with a dielectric constant of over 100. That is, when considering the dielectric constant/film thickness ratio, it is not possible to greatly exceed the performance of conventional polymer thin films.

In addition, solving the temperature dependence and frequency dependence of the dielectric constant is an important issue, and barium titanate cannot be said to be optimal as a composite ceramic. In some cases, it may be preferable to indicate a constant. However, it is difficult to obtain lead titanate as fine particles suitable for use in dielectric films, and even after repeated sieving operations, the maximum particle size is often around 10 pm, and the dielectric constant at room temperature is is 150-
200, which is not practical because it is a piezoelectric material with large anisotropy.

(Solution to the Problem) When considering a polymer composite dielectric, the present inventors developed composite ceramics using an oxalate precipitation synthesis method instead of the conventional oxide mixing method. A method for obtaining a ferroelectric oxide in the form of fine particles was provided (Japanese Patent Application No. 62-9080).

By adopting this method, the entire '11t becomes ipm
The following fine-grained and highly crystalline ceramics can be synthesized, and if necessary, it is also possible to shift the particle size distribution range from maintaining a narrow particle size distribution. In addition, since the constituent elements of the oxalate precipitate are in a uniform, finely dispersed state, the fired products obtained from this are expected to have high performance with little compositional variation.

From the above point of view, the present inventors developed calcium-substituted lead titanate (
(Pbx -x Cax) Ties ) was prepared by the oxalic acid precipitation method, mixed into a blended composition with a rubbery polymeric substance and a resinous polymeric substance, and the dielectric constant was measured, and it was found that 0.35≦ It has been found that a large dielectric constant can be obtained by setting the amount of calcium substitution in the range of X <0.95. Even more surprisingly, the above composition (r) (
It was found that the electromechanical coupling constant in the thickness direction of the Phx -x Cax ) Ties composite is zero even when it is made into a thermoelectret, and the piezoelectric constant d31A in the transverse direction is negligibly low. That is, the present invention was completed by obtaining a highly functional polymer composite dielectric material with a dielectric constant of, for example, over 100, which has piezoelectric properties that are undesirable as a dielectric material. A precipitate composition obtained by contacting an acidic aqueous solution containing lead, calcium, and titanium with oxalic acid dissolved in at least one alcohol selected from the group consisting of ethanol, propanol, pentanol, and hexanol is thermally decomposed. When producing a ferroelectric oxide using
1.02 molar amount and 0.49 to 0.51 per mole of Ti
Ph 1-x Cax
) Tios (however, 0.35≦X<0.95) A polymer composite consisting of a composition containing fine powder of a ferroelectric oxide and a rubbery polymeric substance and/or a resinous polymeric substance. Providing a dielectric (Effects) By manufacturing a polymer composite dielectric according to the method of the present invention, the following effects are achieved.

(1) Produced by the method of the present invention (Pbx -x Ca
w ) Ties, 0.35≦X<0.95 (mole fraction), the value of
, film thickness, flexibility, etc.) can be arbitrarily set within the range of 0 (2) According to the method of the present invention, (Pb1-x Caw)'
l'ios is Pb, Ca, 'I' at the stage of oxalate precipitation.
By setting the quantitative ratio of i to a stoichiometric value and firing in air at 600 to 1200°C, preferably 700 to 1100°C, an oxide in which the stoichiometric ratio is maintained can be obtained.

Since excess Pb can be prevented, there is no abnormal grain growth during firing, and particles with a narrow particle size distribution can be obtained. In addition, when x = o, so, the total particle size can be 1 μm or less when fired at 800°C or less, and 2 μm or less even when fired at 1000°C, so the particle size can be selected according to the purpose and function of the polymer dielectric composite. can do. For example, when making a composite film with a thickness of 1 opm or less, 4100
A powder fired at 0° C. can be used.

(3) According to the method of the present invention, (Pbl-x Cax)T
A polymer composite dielectric material consisting of a composition obtained by mixing ies fine particles with a rubber-like polymer material and a resin-like polymer material is a composite dielectric material obtained by mixing oxide particles with a conventionally known oxide mixing method. The method is disappointing because it gives an unexpectedly high ε value. For example, (Pbo
, to Cao, io ) A polymeric dielectric material made of TiO3, acrylonitrile-butadiene rubber, and polyacetal can provide a property of ε>80 in the region of 1 h.

(4) The polymer dielectric composite obtained by the method of the present invention has the characteristic that it does not exhibit piezoelectric properties even when it is converted into a thermal electret, which is usually done for piezoelectric composites. The (Pbo -x Cax ) Ties powder used in the present invention is 0 (
In the range of x<0.35, a high-performance polymer piezoelectric composite not previously available can be obtained, but in the range of 0.35≦X<0.95, only the dielectric properties of the present invention are selectively expressed.

(5) Used in the present invention (Pbs-xCax)
'['i0s is originally a calcium titanate solid solution of lead titanate, and has excellent characteristics in the high frequency range,
Since it can provide a relatively large dielectric constant even in the high frequency range, it can be applied to low loss capacitors in the high frequency range.

Detailed Description of the Invention (1) Fine powder of ferroelectric oxide gI4M Fine powder of ferroelectric oxide is obtained by adding oxalic acid dissolved in alcohol to an acidic aqueous solution containing lead, calcium, and titanium. The resulting precipitate is fired. Lead, calcium, and titanium are water-soluble compounds, and generally water-soluble salts are used. Pb, Ca.

Nitrate is desirable in order to form a mixed aqueous solution of each Ti ion.

The amounts of each compound of lead, calcium, and titanium are adjusted to the proportions of the desired chemical composition of the ferroelectric oxide.

It is also necessary to keep the solution acidic, and an acid, generally nitric acid, is added that does not precipitate lead, calcium or titanium.

These aqueous solutions can be obtained, for example, by the following method.

Add lead nitrate to a titanium oxynitrate aqueous solution obtained by adding water to a titanium alkoxasite such as titanium tetraisopropoxide, hydrolyzing it, and then reacting the titanium hydroxide with concentrated nitric acid, which is washed with water until the alcohol odor is almost eliminated. and calcium nitrate. The resulting mixed aqueous solution may contain up to 5 mol per mol of titanium, preferably 0.
5-3 moles of nitric acid are added.

To the acidic aqueous solution thus obtained, 0.49 to 0.51 mole, preferably 0.495 to 0.505 mole, and 1 mole each of lead and calcium are added to the acidic aqueous solution obtained per mole of titanium dissolved in the aqueous solution. oxalic acid in a total amount of 0.98 to 1.02 mol, preferably 0.99 to 1.01 mol.

Oxalic acid is added as an alcohol solution, and the alcohol used is at least one selected from the group consisting of ethanol, propanol, phthanol, pentanol, and hexanol, preferably at least one selected from ethanol and propanol.

The amount of alcohol used is 0 per 1 volume of the acidic aqueous solution.
．． 5 to 10 volumes are used, preferably 1 to 5 volumes.

Oxalic acid is added to form a precipitate that becomes a precursor of a ferroelectric oxide, and the acid in the aqueous solution contained in the precipitate is neutralized with amine or ammonia.

Neutralization of the acid can be carried out by adding an amine or aqueous ammonia solution to the aqueous solution in which the precipitate is suspended, and adjusting the pH to 6.2 to 7.5, preferably 6.5 to 7.5.

Moreover, after separating the precipitate, it can also be washed with an amine or aqueous ammonia solution.

The separated precipitate is washed at least once in alcohol and then dried, heated at 600°C or higher at 1200°C even in air.
C. or lower, preferably from 700.degree. C. to 1100.degree. C., the desired fine particle oxide can be obtained.

The amount of Ca replacement (<0.35≦K<0.95) can be controlled to an arbitrary value by adjusting the amount of lead compound and calcium compound added. The range of X is preferably 0.35 to 0
．． 90, more preferably 0.35 to 0685. If it exceeds 0.95, the ε value of the composite dielectric material will be significantly reduced, and the object of the present invention will not be met.

The fine particles obtained by firing do not require pulverization and can be easily dispersed in rubbery polymeric substances and/or resinous polymeric substances.

(2) Preparation of polymer composite dielectric material A rubber-like polymer material and/or resin-like polymer material can be used as the organic component of the polymer composite dielectric material. The organic component can be at least one substance selected from two groups and a combination of substances from each group.

Rubbery polymer substances include natural rubber, SBR, ethylene propylene rubber, silicone rubber, and acrylonitrile.
Butadiene rubber, epichlorohydrin rubber, fluororubber, urethane rubber, etc. can be used, and in particular, acrylonitrile-butadiene rubber, epichlorohydrin rubber,
It is preferable to use fluororubber, urethane rubber, etc. A0
There are no particular limitations on the vitreous polymer, but examples include polyacetal resin, polyfluorine resin, methacrylate resin, polyacrylonitrile resin, polyamide resin, polyimide resin, polyester resin, polyolefin resin, polystyrene resin, polyvinyl chloride resin, and chlorine. It is preferable to use chemically modified polyethylene resin, polycarbonate J@finger, or the like.

An example of a preferred organic component is 0.1 parts by weight of polyacetal resin per 10 parts by weight of acrylonitrile-butadiene rubber.
100 parts by weight, preferably 1 to 50 parts by weight.

The fine particles of ferroelectric oxide can be mixed in an amount of 1 to 200 parts by weight, preferably 2 to 150 parts by weight, per 10 parts by weight of the rubbery polymer and/or resinous polymer.

These mixing methods include kneader, mixing roll,
Any means known as a general mixing method such as an extruder, a plastograph, various mixers, and a ball mill can be used, and as a molding method, an extrusion molding method, a calender molding method, etc. can be used. In addition, the molded product can be made into various shapes such as plate, cylinder, and sheet.◎Also, the resinous polymer is dissolved in an appropriate solvent, and the ferroelectric oxide fine particles are dispersed therein, and then a film is formed. A composite dielectric material can be obtained by using the following method.

In this case, a solvent-soluble rubber-like polymer may also be present.

For polymer composite dielectrics, metal foils, conductive resins, conductive pastes, or metal coatings by vacuum deposition or chemical plating can be used as electrodes, which are usually adhered to the front and back surfaces of the molded body.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 (1) ((Pbo, goCao, 4o)TiOx
Synthesis of fine particles] Commercially available tetraisopropyl titanium 500
Distilled water 70001 LIKfN was added to obtain hydroxide.
After filtering this, washing was repeated three times with 1000111 pure water to obtain titanium hydroxide. This was added to ice-cooled commercially available special grade concentrated nitric acid 20117, left for one day and night, and then filtered to obtain a titanium oxynitrate solution. It was determined by gravimetric analysis with Ti 9 degrees as Ti0z, and 0.1173 t Tl/d was obtained. Mix 40ILt of titanium oxynitrate solution, special grade lead nitrate (purity 99.5%) ss, 5o2or, special grade calcium nitrate-tetrahydrate (purity 99.5%) 32.8915f, special grade nitric acid 76.79d1 ion exchange water 1498d Pb/Ca/Ti-MO,60/O-40/
1.00 (molar ratio), HNOs/Ti = 3
/1 (molar ratio) was obtained and kept at room temperature.

Special grade oxalic acid dihydrate (purity 99.5%) 65.1
8562 was dissolved in special grade ethanol 5145d and kept at room temperature, (COOH)z/(Pb+Ca+Ti) =
A solution of 0.7 s (mole ratio) and ethanol/the acidic aqueous solution = 3/1 (volume ratio) was prepared.

Add the acidic aqueous solution to the vigorously stirred oxalic acid-ethanol solution at a rate of about 22 SD/min to obtain a white slurry liquid,
After the addition was completed, stirring was continued for 5 minutes, and then special grade aqueous ammonia 216.1817 was added to the stirred slurry over about 1 minute, and stirring was continued for an additional 5 minutes.

Measure the pH of the slurry solution using BTB test paper, and
．． I got 2.

Slurry mother liquor and white precipitate cake were separated using a pressure filter.

The obtained white precipitate cake was poured into ethanol 3241d and crushed and washed for 30 minutes, and then the washing liquid and the white cake were separated using a pressure filter. This operation was repeated once more, and the resulting white cake was dried in a pressure filter under nitrogen flow for 1 hour. The resulting semi-dry cake was thinly stretched onto a stainless steel plate whose surface temperature was kept at 150°C to evaporate the ethanol, and then dried at 100°C for 6 hours in a hot pot circulation dryer. Body powder was obtained.

The obtained precursor powder was lightly crushed in an agate mortar and then calcined in a Matsufuru furnace at 1000° C. for 8 hours to obtain the desired oxide powder with a yield of 9B and 3%.

Physical properties of oxide powder The elemental composition ratio of the obtained oxide powder was analyzed using fluorescent X-rays, and it was determined that (Pbo, gocao, 3o) TiO, 5so
A composition value of s was obtained. BET surface area is 1.95 tt/
It was f.

The average primary particle diameter determined from this was 0.53 μm. The particle size distribution measured with a Microtrac particle size meter is shown in FIG.

The X-ray diffraction pattern is shown in FIG. Results of crystal lattice analysis c
/A-axis ratio was 1.01.

(2) Production of polymer composite dielectric material Polyacetal resin (Delrin 500, manufactured by Depond Co., Ltd.) 4V was kneaded on a mixing roll heated to 185°C, and when it was uniformly melted, acrylonitrile-butadiene rubber (
Nippon Zeon Co.'Z, F-1i') 1.51 was added little by little, and the product obtained in (1) was further added (Pbo, s).

Cao, 40) Ties 20.06 t less kfF
- Mix uniformly for 10 minutes while adding.

A sheet having a diameter of 8 cIn and a thickness of 121 μm was produced from the polymer composite using a compression press heated to 185°C. A sheet with a diameter of 2 m is punched out from this sheet using a punch, and a sheet with a diameter of 1 cI is punched out by gold vapor deposition on both sides.
1 electrode and a conductive path with a width of 5 m were formed.

(3) Measuring the gas properties of polymer composite dielectrics Frequency dependence at room temperature of the dielectric constant and dielectric loss of the polymer composite dielectrics obtained in (2) using an LCR meter (YHP-4274A and YHP-4275A) The characteristics were measured and the results shown in Figure 3 were obtained. Furthermore, an impedance analyzer (YHP-4
274A) was used to measure the temperature-dependent characteristics, and the fresh fruits shown in FIGS. 4 and 5 were obtained.

Example 2 Same method as Example 1 (Pbo, 5oCao, go)
Ties powder was obtained. The firing conditions are 1000℃ and 12
It was time. BET surface area z, a s? Fl”／'
, a C/' axial ratio of 1.00, and an average particle diameter of 1.86 μm as measured by a Microtrac particle size meter were obtained as physical properties.

8 tons of polyacetal resin was prepared in the same manner as in Example 1.

ZF-1129 and Cefmix 5.291 were placed on a mixing roll to obtain a sheet with a ridge and a thickness of 500 μm. This sheet was stretched on a calendar roll heated to 190°C and transferred to a PET film to obtain a film with a thickness of 65 μm. Electrodes were deposited on this film, and the frequency dependence characteristics of dielectric constant and dielectric loss at room temperature were measured, and the results shown in Table 1 were obtained.

(Margin below) Table 1

[Brief explanation of the drawing]

Figures 1 to 5 are diagrams showing the physical properties of the ferroelectric oxide obtained in Example-1. Figure 1 is a diagram showing the particle size distribution, and Figure 2 is an X-ray diffraction diagram. , FIG. 3 is a diagram showing the frequency characteristics of 8 and tan δ, FIG. 4 is a diagram showing the - temperature dependence, and FIG. 5 is a diagram showing the temperature dependence of tan δ. Figure 1 grain iso (/, Im) 211th! i

Claims (1)

[Claims] A precipitate composition obtained by contacting an acidic aqueous solution containing lead, calcium, and titanium with oxalic acid dissolved in at least one alcohol selected from the group consisting of ethanol, propanol, pentanol, and hexanol is thermally decomposed. When producing a ferroelectric oxide, the amount of oxalic acid added is 0.98 to 1.02 per mole each of Pb and Ca.
molar amount and a total amount of 0.49 to 0.51 molar amount per mole of Ti, and the acid in the aqueous solution containing the precipitate composition is neutralized with an amine or ammonia. (Pb_1_−_xCa_x)Ti
A polymer composite dielectric consisting of a composition containing a fine powder of a ferroelectric oxide consisting of O_3 (0.35≦x<0.95) and a rubbery polymeric substance and/or a resinous polymeric substance. body.