WO2005021461A1

WO2005021461A1 - Perovskite solid solution composition and piezoelectric ceramics produced therefrom

Info

Publication number: WO2005021461A1
Application number: PCT/JP2004/012354
Authority: WO
Inventors: Ruiping Wang; Yoshiro Shimojo; Tadashi Sekiya; Kunio Matsuzaki
Original assignee: National Institute Of Advanced Industrial Science And Technology
Priority date: 2003-08-28
Filing date: 2004-08-27
Publication date: 2005-03-10
Also published as: JP4491537B2; JPWO2005021461A1

Abstract

A perovskite solid solution which comprises potassium sodium niobate (K1-xNax)NbO3 and one of a perovskite type oxide M1M2O3 and a simple oxide M32O3, wherein M1 represents a metal ion, such as Mg, Ca, Sr, Ba, Bi, La, Y, Ce or Pr, which is capable of selectively entering into a perovskite A site and is exclusive of lead, M2 represents a trivalent or tetravalent metal ion, such as Ti, Zr, Ga, In, Ni, Mn or Fe, which is capable of selectively entering into a perovskite B site, M3 represents a trivalent metal ion, such as Bi, La, Y, Ce, Pr, Nd or Fe, which is capable of selectively entering into a perovskite A or B site, and x represents a number of 0.4 ≤ x ≤ 0.6. The above perovskite solid solution is completely free of lead and thus is friendly to the environment and also a piezoelectric ceramics being composed of the solid solution exhibits displacement characteristics tremendously higher than those of conventional piezoelectric materials used practically which are mainly PZT type ceramics.

Description

Specification

Perovskite solid solution composition and piezoelectric ceramics obtained therefrom

[0001] The present invention relates to a perovskite toy conjugate, sodium niobate (NaNbO) and potassium niobate (KNbO), which are composed mainly of different perovskite compounds such as BaTiO, SrTiO, and CaTiO. The present invention relates to a perovskite solid solution composition having a composition in which an oxide is added in an amount of about several mol%, and a piezoelectric ceramic obtained by sintering the composition.

^ Scenic technology

[0002] Piezoelectric ceramics undergo elongation deformation when a voltage is applied, and as an actuator such as an ultrasonic vibrator, an ultrasonic motor, a precision positioning element, or a piezoelectric transformer, a voltage is generated when a piezoelectric ceramic is deformed. It has a wide range of applications as sensors, sensors for piezoelectric gyros for car navigation systems, sonars, ultrasonic diagnostic devices, etc. In recent years, there has been a growing trend to make various machine systems intelligent, which has increased the importance of factories in particular. At present, the mainstream of piezoelectric ceramics widely used is mainly composed of lead zirconate titanate (PZT).

[0003] The piezoelectricity of this PZT ceramic is brought about by the combination of antiferroelectric lead zirconate (PbZrO) with a rhombohedral structure and ferroelectric lead titanate (PbTiO) with a tetragonal structure. In the composition near the rhombohedral phase and the tetragonal phase boundary (Mo 卬 hotropic phase boundary, MPB, around PbZrO / PbTiO = 52/48), it is the highest. For this reason, many PZT-based piezoelectric ceramics are used with a composition near the MPB. The reason for this is that the instability is introduced into the perovskite structure, and the electrical sensitivity is increased, resulting in high electrical displacement.

[0004] In recent years, there has been an increasing trend to use piezoelectric ceramics as an actuator for vibration control of aircraft, automobiles, railcars, ships, etc. and for vibration isolation of civil engineering structures. since PZT ceramics practically possible electrostrictive (Δ L / L) Hasere, ze les, and in 2x10- ³ (0.2%) or in, also the piezoelectric constant d of the longitudinal effect is about 300- 600pC / N, Piezoelectric ceramic materials that are insufficient to meet such demands and exhibit high displacement and high output characteristics The development of a fee is desired.

[0005] On the other hand, recently, there has been a movement to reduce the amount of lead from various materials due to the problem of global environmental pollution, and piezoelectric ceramics are no exception. In fact, most of the currently widely used piezoelectric ceramics, such as PZT ceramics, contain large amounts of lead. Europe is taking the lead issue seriously, and it may soon be impossible to export lead-containing products from Japan to Japan. In view of such circumstances, research and development of low-lead or lead-free piezoelectric ceramic materials are currently being actively conducted in various fields, but at present, low-lead or low-lead piezoelectric ceramics exhibiting piezoelectric properties comparable to PZT ceramics. -Based or lead-free piezoelectric ceramic materials were born.

[0006] In order to solve these problems, the present inventors have previously proposed a NaNbO-KNbO-PbTiO-based piezoelectric ceramic material as a low-lead-based piezoelectric ceramic (Patent Document 1).

3 3 3

Although this piezoelectric ceramic material has excellent characteristics such as extremely high electric displacement, despite its lead content being significantly reduced as compared with conventional ones, it still has a composition containing lead. Met.

Therefore, if an actuator material can be obtained that is completely lead-free rather than low-lead and exhibits properties equal to or better than PZT ceramics, it is expected to improve the environmental pollution problem and have an immeasurable economic ripple effect. it can.

[0007] Patent Document 1: Japanese Patent Application No. 2003-040125

Disclosure of the invention

Problems to be solved by the invention

[0008] The present invention is a further development of the proposal of the above-mentioned Japanese Patent Application No. 2003-040125, which is completely lead-free and has been used in a conventional piezoelectric device mainly made of PZT ceramics. It is an object of the present invention to provide a novel environmentally friendly solid solution composition exhibiting a displacement characteristic significantly higher than that of a material and a piezoelectric ceramic obtained from the composition.

Means for solving the problem

[0009] The present inventors have completed the NaNbO-KNbO-PbTiO-based low-lead piezoelectric ceramics previously filed.

3 3 3

Effect of adding various oxides on NaNbO-KNbO for the purpose of total lead-free

3 3

As a result of thorough research, it was found that instead of PbTiO, lead-free powders such as BaTiO, SrTiO, and CaTiO It has been found that the addition of buskite and the use of simple oxides, not perovskite oxides, can provide an electrical displacement equivalent to or greater than that of PbTiO.

Three

The invention of lead-free high-performance piezoelectric ceramics has been completed.

That is, according to the present invention, the following inventions are provided.

(1) Perovskite potassium sodium niobate (K Na) NbO and perovskite oxide

1

Perovskite containing M1M20 and represented by the general formula (l_y) (K Na) NbO-yMlM20

1

Solid solution composition.

(Where M1M20 is a divalent Ml metal ion (excluding lead) and a tetravalent M2 metal ion

Three

A trivalent Ml metal ion that can selectively enter the alobskite-type oxide or perovskite-type oxide A site and a trivalent M2 metal ion that can selectively enter the perovskite-type oxide B site Represents a lobskite-type oxide. X and y represent numerical values in the range of 0.4≤x≤0.6 and 0 <y≤0.1, respectively. However, when Ml = Ba and M2 = Ti, the y range is 0 <y <0.05. )

(2) Perovskite potassium sodium niobate (K Na) NbO and oxide of trivalent metal M30

Perovskite solid solution composition containing l 3 2 3 (l-z) (K Na) NbO _z M3 O

l 3 2 3.

(In the formula, M3 represents a trivalent metal ion that can selectively enter the perovskite A or B site. X and z represent numerical values in the range of 0.4≤x≤0.6 and 0 <z≤0.1, respectively.)

(3) An open bouskite solid solution piezoelectric ceramic obtained by sintering the perovskite solid solution composition according to (1) or (2).

(4) The perovskite solid solution piezoelectric ceramic according to the above (1) or (2), which is densely sintered to a relative density of 95% or more. The invention's effect

The piezoelectric ceramic according to the present invention is a new environmentally friendly high-performance piezoelectric ceramic material because it has a significantly improved electrical displacement than conventional materials represented by the PZT system and does not contain lead. It opens the way for expanding applications. As with the PZT ceramics, the ceramics of the present invention include actuators such as ultrasonic vibrators, ultrasonic motors, precision positioning elements, piezoelectric transformers, acceleration sensors, piezoelectric gyros for car navigation systems, sonars, ultrasonic diagnostic elements, etc. Used in aircraft, automobiles, railway vehicles, ships It is also expected to have new applications as an actuator for vibration control of ships and vibration isolation of civil engineering buildings.

BEST MODE FOR CARRYING OUT THE INVENTION

[0011] As described above, the present inventors have set forth NaNbO in the invention of Japanese Patent Application No. 2003-040125.

Proposed power of -KNbO-PbTiO-based low-lead piezoelectric ceramics Through subsequent studies, it was determined that the reason why the low-lead piezoelectric ceramics provided excellent electrical displacement characteristics was due to the following reasons.

[0012] The addition of PbTiO to NaNbO -KNbO system ^{^{perovskite, (Na +, K +,}} Pb 2+) (Nb 5+, Ti 4+) as 0, A-site ions (Na ^+, K ⁺⁾ Part is Pb ²⁺ and part of B site ion (Nb ⁵⁺ ) is perovskite replaced by Ή ⁴⁺ . At this time, Pb ²⁺ and Ή ⁴⁺ have different ion sizes and valences as compared with the original ions, so that instability is introduced into the crystal lattice and the size of the formed ferroelectric domain is reduced. The smaller the size of the ferroelectric domain, the easier it is for the applied electric field to rotate, so that the electric field induced strain also increases. It is considered that the reason why the NaNbO-KNbO-PbTiO-based high-density sintered body exhibits high piezoelectricity is that the properties of the domain structure are changed in this way.

[0013] That is, the electric field-induced strain characteristics of ferroelectric ceramics are affected by the ease of rotation of the ferroelectric domain, and the electric field-induced strain increases as the ease of rotation increases. Therefore,

The oxide added to NaNbO-KNbO is not particularly limited to PbTiO but its ion size or valence power SNa ⁺ , KNb ⁵⁺

The effect of improving the electric field induced strain characteristics of -KNbO is expected. Therefore, the present inventors

After accumulating experimental examples in which lead-free perovskites such as BaTiO, SrTiO, and CaTiO were added instead of PbTiO, the conclusion was reached that the above hypothesis was correct. In addition, even if a trivalent simple metal oxide is added instead of the perovskite oxide, a difference in ion size valence can occur. When this simple oxide is added to perovskite, its metal ions selectively enter either the A or B site of the perovskite lattice, but one of them becomes a lattice defect due to the balance of charge. . In any case, it was confirmed that the addition of the simple oxide to NaNbO-KNbO had the same effect as the addition of the different perovskite. The perovskite solid solution composition according to the present invention contains (i) perovskite-type potassium sodium niobate Na) NbO and perovskite-type oxide M1M20, and has a general formula

l 3 3

a mixed oxide represented by (l-y) (KNa) NbO-yMlM20, or (ii) a perovskite-type

Mixed oxide consisting of potassium sodium borate (K Na) NbO and oxide of trivalent metal M30

l 3 2 3

The main component is (l-z) (K Na) NbO 2 -zM 3 O.

l 3 2 3

Where M1M20 is a divalent Ml metal ion (except for lead and lead) and a tetravalent M2 metal ion

Three

Trivalent Ml metal ions that can selectively enter the perovskite-type oxide or perovskite-type oxide B site, and trivalent M2 metal ion forces that can selectively enter the perovskite-type oxide B site Represents a perovskite oxide. x, y, and z represent numerical values in the range of 0.4≤x≤0.6, 0 <y≤0.1, and 0 <ζ≤0.1. However, when Ml = Ba and M2 = Ti, the y range is 0 <y <0.05.

Specific examples of Ml include divalent or trivalent metal ions (excluding lead) that can selectively enter the perovskite A site. For example, Mg, Ca, Sr, Ba, Bi, La , Y, Ce, Pr and the like are exemplified, and among them, Ba, Sr, Ca and the like are preferable.

Specific examples of M2 include tetravalent or trivalent metal ions that can selectively enter the perovskite B site.Examples include Ti, Zr, Sc, Ga, In, Zn, and Fe. Among them, Ti and Zr are preferable.

Specific examples of M3 include trivalent metal ions that can selectively enter the perovskite A or B site, and examples thereof include Bi, La, Y, Ce, Pr, Nd, and Fe. , La and Y are preferred. χ represents a numerical value in the range of 0 · 4≤χ≤0.6.

In the above (i) and (ii), the perovskite oxide M1M20 or the acid of a trivalent metal

Three

The use ratio of the compound M30 is {potassium sodium niobate (K Na) Nb}

It is at most 10 mol%, preferably at most 5 mol%, based on 23 l3.

[0015] The perovskite solid solution composition according to the present invention comprises potassium sodium niobate.

(K, Na) NbO as a main component, to which other perovskite oxidation of 10 mol% or less

Three

(M1M20) or a trivalent simple metal oxide (M30).

3 2 3

As raw materials, various forms such as carbonates, oxalates, nitrates, hydroxides and oxides can be used, and these raw materials are mixed into a predetermined composition to obtain a final composition. It may be prepared as follows.

The perovskite solid solution composition of the present invention can be made into a piezoelectric ceramic by densely sintering the perovskite solid solution composition preferably at a relative density of 95% or more.

Such sintering means is not limited, but if it can be sintered under normal pressure, it would be better than that. However, since sintering of KNbO-NaNbO-based materials is difficult, it is desirable to adopt a pressure and heat sintering method that can sinter under pressure in order to obtain a high-density sintered body efficiently.

[0017] Examples of such pressure heating and sintering methods include a spark plasma sintering method (hereinafter, referred to as an SPS method), a hot press method (hereinafter, referred to as an HP method), an anvil method, and a HIP method. (Hot isostatic method) and the like, and the methods preferably used in the present invention are the SPS method and the HP method.

[0018] The SPS method is a technique in which a DC pulse current is applied to a sample in a pressurized state, and grain boundary diffusion and particle bonding are caused by using the high energy of high-temperature plasma instantaneously generated by spark discharge. Recently, it has attracted attention as a high-speed sintering method for ceramics.

[0019] In this SPS method, sintering is completed in a short time of about 15 minutes or less, including the time of temperature rise and holding, so that a large amount of easily evaporable components (particularly Na and K) are generated like the NaNbO-KNbO system. This method is the most preferable as a sintering method for a material that includes a composition fluctuation due to heating.

[0020] By the way, as seen in the earlier Japanese Patent Application No. 2003-040125, as a result of applying the SPS method to the NaNbO-KNbO-PbTiO system, most of the compositions were converted to sintered bodies with a relative density of 96% or more. It has been demonstrated that the SPS method has a remarkable effect on densification, and that the piezoelectric displacement characteristics of the obtained ceramics are also dramatically improved.

An example of a method for producing the piezoelectric ceramic of the present invention by the SPS method or the HP method will be described.

First, the main raw materials of KCO, NaCO and Nb0 and the oxides as additives are blended so as to have a desired perovskite composition, and calcined until a perovskite solid solution single phase is obtained.

⁷ sword w--Repeat the mixing process. The calcination conditions vary depending on the type and composition of the raw materials. Normally, the temperature is 850 1000 ° C and the time is 210 hours. The thus obtained ceramic powder is subjected to the SPS method or the HP method.

[0022] The SPS treatment can be performed using, for example, an apparatus such as an SPS-1030 apparatus manufactured by Sumitomo Coal Mining. Bye, Specifically, after filling an appropriate amount of a sample into a graphite die, and applying a DC on / off pulse to the upper and lower punches in a vacuum while applying pressure from above and below using a Dallaphite punch, the desired sintered body can be obtained. Is obtained. In this SPS method, the sample reaches a predetermined temperature in about 5 minutes, and is sintered by holding that temperature for about 5 minutes. The sintering temperature varies depending on the composition, but is in the range of 1020-1100 ° C. The obtained sintered body has a diameter of 15 mm and a thickness of 34 mm, and the relative density reaches 96% or more.

The HP method may be performed using an apparatus such as a PRESS-VAC-2 type apparatus manufactured by Tokyo Vacuum Co., Ltd. In the HP method, the sample is placed in a graphite die and pressed with upper and lower punches. The force S is the same as in the SPS method, and heating is performed by an external heater mounted around the die.

First, an appropriate amount of the calcined ceramic powder is filled in a graphite die, and then the air is evacuated. The external heater is energized and heated while applying pressure from above and below with a graphite punch. In this hot pressing method, the temperature reaches a predetermined temperature (1100 ° C) in about 2 hours. By maintaining the temperature for about 5 to 10 minutes, a sintered body with a relative density of 95% or more can be obtained.

[0024] Since both the SPS method and the HP method use a graphite die in a vacuum, the sintered body cannot be reduced to some extent, and the force S obtained by blackening by mixing a reducing component and then the oxygen S It is whitened by annealing in an atmosphere, for example, at 950 ° C for about 5 hours.

[0025] Both the SPS method and the HP method are effective means for obtaining high-density ceramics that cannot be achieved by the normal-pressure method. Somewhat concerned

. Incidentally, a chemical analysis of the NaNbO-KNbO-PbTiO-based ceramics [1] obtained by the SPS method confirmed that there was no significant variation between the charged composition and the final product composition.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples.

The perovskite solid solution composition of the present invention was sintered using the above-described SPS device and HP device. In order to evaluate the piezoelectric properties, the obtained ceramic was cut out into a plate of 5 mm X 5 mm X 0.5 mm size, mirror-polished on both sides, and a gold sputtered film was applied. And Next, the polarization was performed at room temperature under the condition of 111, and the relationship between applied voltage and electric displacement was examined using a laser displacement meter.

[0027] Table 1 shows the composition, manufacturing method, and sintering density of the perovskite ceramics of the present invention. Table 2 shows the phase transition temperature t, relative dielectric constant, dielectric loss, and electromechanical c of the perovskite ceramics of the present invention.

It shows the coupling coefficient kp, frequency constant Nr, and maximum distortion.

Although the relative density of the obtained ceramics varies slightly depending on the composition and manufacturing method, 96% or more was obtained in most samples, and both the SPS method and the HP method increased the density of the ceramics of the present invention. It has been proved to be effective as a means for performing

Example 11

In this example group, BaTiO was added to (Na K) NbO composition.

0.5 0.5 3 3、2、4mol%

It relates to ceramics obtained by SPS processing. The displacements at 80 kV m are 0.9%, 0.6%, and 0.6%, respectively, which are high values, and high-performance piezoelectric materials are produced even with the NaNbO-KNbO-BaTiO system.

3 3 3

It is found that this can be achieved. Also, the smaller the amount of BaTiO added, the higher the phase transition temperature t

It is clear that the electromechanical coupling coefficient kp and the frequency constant Nr are excellent.

Example 4-1-5

In these examples, BaTiO is used for (Na K) NbO or (Na K) NbO composition.

0.6 0.4 3 0.4 0.6 3 3

Ceramics were obtained by subjecting 2 mol% added to HP treatment. It can be seen that the electric displacement of the obtained ceramic shows a high value of 0.3% -0.5%. (Na K) NbO base

Comparing 0.6 0.43 with (Na K) NbO base, it seems that the one based on (Na K) NbO is somewhat higher

0.4 0.6 3 0.4 0.6 3

It is.

Example 6—7

These are based on (Na K) NbO composition with SrTiO 2

It relates to ceramics obtained by adding 0.4, 0.633, and 8 mol% to HP. The displacement at 80 kV m is 0.2%.

Example 8—10

These are based on (Na K) NbO composition with SrTiO 1

33 Add 3, 3, 5 and 10 mol% to the SPS

0.5 0.5

On ceramics obtained by processing. The displacement at 80 kV m is NaNbO-KNbO-PbTiO

Although it is inferior to the case of the 33 3 system and NaNbO-KNbO-PbTiO system, it is almost the same as that of the PZT system.

3 3 3

Comparable values. Also, in Examples 8-10, Ca was introduced instead of Sr. Similar results were obtained.

Example 11-14

They relate to ceramics obtained by subjecting (Na K) NbO composition with BaZrO or SrZrO to SPS treatment. The maximum strain is in the range of 0.2-0.4%, which is somewhat lower than NaNb〇-KNbO-BaTiO or NaNb〇-KNbO-SrTiO system.

[0033] As described above, in Examples 1-114, various typical examples for the NaNbO-KNbO system were used.

Although the effects of the addition of the oxides of the oxide type have been shown, it is clear that other perovskite-type compounds, which were not shown in these examples, show the same effects as those seen from the above theory.

Example 15-18

In these examples, trivalent metal oxides La 0 and Bi 0 capable of selectively substituting a viscous A-site with respect to the composition of (Na K) NbO were added, and a ceramic was prepared by HP. The electric displacement of the obtained ceramics was in the range of 0.15 to 0.25%, which was almost comparable to that of the PZT system.

[Table 1]

M1M20 ₃ of M3 ₂ 0 _3-containing steel relative density Example Ml M2 M3 X

Content y Weight Z Method (¾)

1 Ba Ti 0.5 0.01 SPS 98

2 Ba Ti 0.5 0.02 SPS 96

3 Ba Ti 0.5 0.04 SPS 97

4 Ba Ti 0.4 0.02 HP 98

5 Ba Ti 0.6 0.02 HP 96

6 Sr Ti 0.4 0.02 HP 97

7 Sr Ti 0.4 0.08 HP 96

8 Sr Ti 0.5 0.01 SPS 96

9 Sr Ti 0.5 0.05 SPS 96

10 Sr Ti 0.5 0.10 SPS 96

11 Ba Zr 0.5 0.01 SPS 99

12 Ba Zr 0.5 0.05 SPS 97

13 Sr Zr 0.5 0.01 SPS 98

14 Sr Zr 0.5 0.04 SPS 98

15 La 0.5 0.01 HP 96

16 La 0.5 0.05 HP 97

17 Bi 0.5 0.01 HP 95

18 Bi 0.5 0.05 HP 96 2]

Claims

The scope of the claims

[1] Perovskite-type potassium sodium niobate (K Na) NbO and perovskite-type oxide

13

Perovskite solid containing M1M20 and represented by the general formula (1-y) (K Na) NbO-yMlM20

3 1 3 3

Solution composition.

Three

Perovskite-type oxides or trivalent Ml metal ions that can selectively enter the perovskite-type oxide A site and trivalent M2 metal ions that can selectively enter the perovskite-type oxide B site Represents a perovskite oxide. X and _y represent numerical values in the range of 0.4≤x≤0.6 and 0 <y≤0.1, respectively. However, when Ml = Ba and M2 = Ti, the y range is 0 <y <0.05. )

[2] Perovskite-type potassium sodium niobate oxide (K Na) NbO and oxide of trivalent metal

13

{Rovskite solid solution composition (l-z) (K Na) NbO 2 -zM3} containing M30.

2 3 1 3 2 3

(Where M3 represents a trivalent metal ion that can selectively enter the perovskite A or B site

. X and z represent numerical values in the range of 0.4≤x≤0.6 and 0 <z≤0.1, respectively. )

[3] An open bouskite solid solution piezoelectric ceramic obtained by sintering the perovskite solid solution composition according to claim 1 or 2.

[4] The perovskite solid solution piezoelectric ceramic according to claim 1 or 2, characterized in that it is densely sintered to a relative density of 95% or more.

INTERNATIONAL SEARCH REPORT International application No.

PCT / JP2004 / 012354

A. CLASSIFICATION OF SUBJECT MATTER

Int. CI ⁷ C04B35 / 495, H01L41 / 18

According to International Patent Classification (IPC) or to both national classification and IPC

B. „FIELDS SEARCHED

Minimum documentation searched (classification system followed by classification symbols)

Int.CI ⁷ C04B35 / 42- 35/50, C04B35 / 00, H01L41 / 18

Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched

Jitsuyo Shinan Koho 1926-1996 Toroka Jitsuyo Shinan Koho 1994-2004

Kokai Jitsuyo Shinan Koho 1971-2004 Jitsuyo Shinan Toroku Koho 1996-2004

Electronic data base consulted during the international search (name of data base and, where practicable, search terms used)

CA, REGISTRY (STN)

C. DOCUMENTS CONSIDERED TO BE RELEVANT

Category * Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No.

A JP 2002-338351 A (TDK Corp.), 1,3,4

27 November, 2002 (27.11.02),

Claims

(Family: none)

A JP 2002-137966 A (Kyocera Corp.), 1,3,4

14 May, 2002 (14.05.02),

Claims

(Family: none)

X JP 2002-68835 A (Toyota Central Research And 2-4

Development Laboratories, Inc.),

08 March, 2002 (08.03.02),

Claims; tables 1, 3

(Family: none)

I ^x 1 Further documents are listed in the continuation of Box C. | J See patent family annex.

* Special categories of cited documents: "T" later document published after the international filing date or priority

"A" document defining the general state of the art which is not considered date and not in conflict with the application but cited to understand to be of particular relevance the principle or theory underlying tiie invention

"E" earlier application or patent but published on or after the international "X" document of particular relevance; the claimed invention cannot be filing date considered novel or cannot be considered to involve an inventive

"L" document which may throw doubts on priority claim (s) or which is step hen the document is taken alone

cited to establish the publication date of another citation or other "Y" document of particular relevance; the claimed invention cannot be special reason (as specified) considered to involve an inventive step when the document is

"O" document referring to an oral disclosure, use, exhibition or other means combined with one or more other such documents, such combination

"P" document published prior to the international filing date but later than being obvious to a person skilled in the art

the priority date claimed "&" document member of the same patent family

Date of the actual completion of the international search Date of mailing of the international search report

14 September, 2004 (14.09.04) 28 September, 2004 (28.09.04)

Name and mailing address of the ISA / Authorized officer

Japanese Patent Office

Facsimile No. Telephone No.

Form PCT / ISA / 210 (second sheet) (January 2004) INTERNATIONAL SEARCH REPORT International application No.

PCT / JP2004 / 012354

C (Continuation). DOCUMENTS CONSIDERED TO BE RELEVANT

X JP 2003-55048 A (Toyota Central Research And 2-4

Development Laboratories, Inc.),

26 February, 2003 (26.02.03),

Claims; table 1

& DE 10237291 Al

X JP 7-82024 A (Murata Mfg. Co. Ltd.) 2-4

28 'March, 1995 (28.03.95),

Claims

(Family: none)

Form PCT / ISA / 210 (continuation of second sheet) (January 2004)