JP2009162528A - Piezoelectric sensor and sensing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a compact piezoelectric sensor, which detects an object to be measured in a sample liquid through the use of a Langevin piezoelectric transducer of 9 MHz or less, secure a high precision in measurement, reduce variations in CI values between piezoelectric sensors, and perform highly precise measurements. <P>SOLUTION: A quartz sensor is provided with the piezoelectric transducer. The piezoelectric transducer is provided with a circular exciting electrode and a band-like extraction electrode extracted from the exciting electrode and electrically connected to the electrode on each of one surface side and the other surface side of a circular piezoelectric piece. The exciting electrode on the other surface side is provided for a wiring board in such a way as to block a recession part so as to face the recession part. In the piezoelectric transducer, a ratio of the diameter of a piezoelectric piece to the thickness of the piezoelectric piece is 50 or less, and the frequency of principal oscillations is 9 MHz or less. The percentage of the area of the exciting electrode to that of the piezoelectric piece is between 60-70%. The size of the breadth of the extraction electrode is 0.3 of the size of the diameter of the exciting electrode or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes a piezoelectric vibrator configured such that an excitation electrode provided on one surface side of a piezoelectric piece contacts a measurement atmosphere and an excitation electrode provided on the other surface side faces an airtight space. The present invention relates to a piezoelectric sensor that senses a measurement object by detecting a change in the natural frequency of a child, and a sensing device that uses this piezoelectric sensor.

  To detect the presence of trace substances in the sample liquid, for example, environmental pollutants such as dioxin, disease markers such as hepatitis C virus and C-reactive protein (CPR), and to measure these substances, crystal vibration A measurement method using a crystal sensor including a child and a measuring instrument that is electrically connected to the crystal sensor and includes an oscillation circuit for oscillating the crystal resonator is widely known (for example, a patent) Reference 1).

  Specifically, the measurement method includes, for example, a plate-shaped crystal piece and a pair of foil-like excitation electrodes (a pair of foil-like excitation electrodes provided so as to sandwich the crystal piece on one side and the other side of the crystal piece) A quartz sensor including a crystal resonator called a Langevin type with an excitation electrode) is configured so that the electrode on one side contacts the measurement atmosphere (sample solution) and the electrode on the other side faces the airtight space When the measurement target substance in the sample solution comes into contact with the electrode on the one surface side, the characteristic that the natural frequency of the quartz crystal fluctuates according to the mass of the contacted substance is utilized.

  As described above, only one side of the crystal unit is brought into contact with the measurement atmosphere and the other side faces the airtight space. It is because it is preferable to do. In the above measurement, the measurement target substance in the sample liquid may be measured based on physical adsorption on the surface of the excitation electrode. However, the measurement target substance is formed on the surface of the electrode on the one side. In some cases, an adsorption layer composed of a substance that selectively chemically bonds to the above is provided, and the measurement target substance is chemically adsorbed to the adsorption layer to perform measurement.

  FIG. 10 shows an example of the configuration around the crystal resonator provided in the crystal sensor. In FIG. 10, reference numeral 11 denotes a wiring board, and the crystal resonator 10 is placed on the wiring board 11. This crystal resonator 10 is provided with a circular excitation electrode 13 and a strip-shaped extraction electrode 13 a extracted from the excitation electrode 13 on one side and the other side of a circular crystal piece 12, respectively. The lead electrode 13a is electrically connected to an electrode provided on the wiring board 11 side.

  Reference numeral 14 in FIG. 10 denotes a through-hole formed in the wiring substrate 11 in the thickness direction, and reference numeral 15 in FIG. 10 denotes a sealing member that closes the through-hole 14 from the back side of the substrate 11. A region surrounded by the sealing member 15, the through hole 14, and the crystal resonator 10 forms an airtight space, and the excitation electrode 13 on the back side of the crystal resonator 10 faces the airtight space. Reference numeral 16 in FIG. 10 denotes a plate-like crystal pressing member made of rubber or the like, and presses the crystal resonator 10 against the substrate 11 to fix the position thereof.

  Reference numeral 17 in FIG. 10 denotes an opening provided so as to penetrate the crystal pressing member 16 in the thickness direction, and faces the excitation electrode 13 on the surface side of the crystal resonator 10. Reference numeral 18 in FIG. 11 denotes an annular protrusion of the crystal pressing member 16. A predetermined amount of sample liquid is stored in a liquid storage space 19 surrounded by the opening 17 and the annular protrusion 18, and the excitation electrode 13 is in contact with the measurement atmosphere.

  By the way, in the crystal sensor as described above, the crystal piece 12 having a frequency of 9.2 MHz is used for the ease of signal processing in the measuring instrument body at the subsequent stage. Since the thickness of the crystal piece and the frequency of the crystal piece have a corresponding relationship, when the frequency of the crystal piece 12 is 9.2 MHz, the thickness t of the crystal piece 12 is 182 μm. Further, in order to meet the demand for a crystal sensor that is becoming smaller in size, the diameter D of the crystal piece 12 is set to 8.7 mm. As a result, the crystal piece 12 has a ratio of the diameter D of the crystal piece 12 to the thickness t of the crystal piece 12 (hereinafter referred to as a side ratio D / t) of 47.802. On the other hand, in order to suppress a decrease in measurement sensitivity, the area of the excitation electrode 13 must be increased to some extent, for example, set to a diameter of 7 mm.

  However, when the side ratio D / t of the crystal piece 12 is reduced in this way and the ratio of the area of the excitation electrode 13 to the area of the crystal piece 12 is 50% or more, the vibration of the crystal unit 10 is extracted from the excitation electrode 13. The ratio of leakage to the electrode 13a increases, and the vibration energy of the thickness-slip mode that is the main vibration is not sufficiently concentrated on the center portion of the crystal piece 12, as shown in FIG. 3B described in the embodiment. A phenomenon of reaching the end of the crystal piece 12 occurs. Since the peripheral edge portion of the crystal piece 12 is pressed by the annular protrusion 18 of the crystal holding member 16, when the vibration energy spreads to the end portion of the crystal piece 12, the crystal piece 12 is interposed between the crystal sensors by the annular protrusion 18. As a result, the vibration mode varies, and as a result, the crystal impedance (CI) value varies among the quartz sensors.

  On the other hand, in order to suppress the phenomenon described above, the main vibration energy can be concentrated in the central portion by polishing both ends of the crystal piece and adding a bevel to increase the creepage distance. Since it is necessary to press the peripheral edge with the annular protrusion 18 of the crystal pressing member 16 to prevent liquid leakage, the bevel must be provided outside the pressing surface of the crystal piece 12, and the crystal sensor itself becomes larger. This would be against the above request.

  Further, the diameter D of the crystal piece 12 to which the bevel is added is set to 8.7 mm, and the formation area of the excitation electrode on the surface of the crystal piece 12 is reduced, so that the pressing surface of the annular protrusion 18 can be secured in the crystal piece 12. Since the excitation electrode area is reduced, the sensitivity of the quartz sensor is lowered, and it is difficult to achieve the intended purpose of the quartz sensor.

JP 2006-194866 A

  The present invention has been made in view of such circumstances, and an object thereof is to achieve downsizing in a piezoelectric sensor that detects an object to be measured in a sample liquid using a Langevin type piezoelectric vibrator of 9 MHz or less, It is another object of the present invention to provide a technique capable of ensuring high measurement accuracy and performing high-precision measurement while suppressing variations in CI values between piezoelectric sensors.

The present invention relates to a piezoelectric sensor that is electrically connected to a measuring instrument body in order to detect an object to be measured in a sample liquid.
A wiring board provided with a connection terminal part connected to the measuring instrument main body, and on one side thereof, an electrode electrically connected to the connection terminal part and a recess for constituting an airtight space;
A circular excitation electrode is provided on one surface side and the other surface side of the circular piezoelectric piece, and a strip-shaped extraction electrode is provided from the excitation electrode and electrically connected to the electrode. The excitation electrode on the side is provided on the wiring board so as to face the recess, and the ratio of the diameter of the piezoelectric piece to the thickness of the piezoelectric piece is 50 or less, and the frequency of the main vibration is 9 MHz or less. A piezoelectric vibrator;
A liquid storage space having a bottom surface on one surface side of the piezoelectric vibrator is formed, and is provided so as to surround the liquid storage space. The piezoelectric resonator is formed by pressing an outer portion of the concave portion on the one surface side of the piezoelectric vibrator toward the wiring board side. A holding member made of an elastic material having an annular protrusion for fixing the position of the vibrator;
A liquid injection cover that covers the pressing member facing the wiring substrate, communicates with the liquid storage space on the surface thereof, and is provided with an injection port for injecting a sample liquid into the liquid storage space. ,
The ratio of the area of the excitation electrode to the piezoelectric piece is 60 to 70%, and the width of the extraction electrode is set to 0.3 or less of the diameter of the excitation electrode. Note that the frequency of the main vibration being 9 MHz or less specifically means 9.5 MHz or less.

  The piezoelectric vibrator includes an excitation electrode provided on one surface side of the piezoelectric piece, and an adsorption layer formed on the surface of the excitation electrode for adsorbing the sensing object. You may comprise so that a natural frequency may change.

  Further, the sensing device of the present invention includes the above-described piezoelectric sensor, and a measuring instrument main body that detects the natural frequency of the piezoelectric vibrator and detects a measurement object in the sample liquid based on the detection result. It is characterized by.

  According to the present invention, in a Langevin type piezoelectric sensor using a piezoelectric vibrator of 9 MHz or less, in order to reduce the size and secure high sensitivity, the side ratio is 50 or less and the area ratio is 50% or more. There must be. However, with such a configuration, the amount of vibration leaking from the excitation electrode to the extraction electrode increases as described above. Therefore, by setting the area ratio to 70% at most and making the width of the extraction electrode not more than 0.3 of the diameter of the excitation electrode, the main vibration of the vibrator hardly leaks from the excitation electrode to the extraction electrode. Thus, the vibration energy is concentrated at the center of the piezoelectric piece. For this reason, even if there is a variation in the stress applied to the piezoelectric piece due to the annular protrusion of the pressing member between the piezoelectric sensors, the variation in the vibration mode is suppressed, and the variation in the crystal impedance (CI) value in the piezoelectric sensor as shown in the embodiments described later. Is suppressed.

  An embodiment of a crystal sensor which is an example of a piezoelectric sensor according to the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view showing a quartz sensor 20 which is an example of a piezoelectric sensor according to the present invention, and FIG. 2 is a plan view showing the structure of a quartz vibrator 2 which is a piezoelectric vibrator provided in the piezoelectric sensor. It is. 4 is a perspective view of the crystal sensor 20, and FIG. 5 is an exploded perspective view showing the upper surface side of each component of the crystal sensor 20. As shown in FIG. As shown in FIGS. 1, 4 and 5, the quartz sensor 20 has the sealing member 3A, the wiring board 3, the quartz crystal resonator 2, the quartz pressing member 4, and the liquid injection cover 5 stacked in this order from the bottom. It is constituted by.

  As shown in FIG. 1, the crystal resonator 2 includes a crystal piece 21 that is a piezoelectric piece, excitation electrodes 22 and 23, and extraction electrodes 24 and 25. The configuration of the crystal resonator 2 will be described in detail with reference to FIG. The crystal sensor 20 uses a crystal piece 21 having a frequency of 9 MHz or less, in this example, 9.2 MHz, for ease of signal processing in a measuring instrument body, which will be described later. Since the thickness t of the crystal piece 21 has a corresponding relationship with the frequency of the crystal piece 21, the thickness t of the crystal piece 21 is 182 μm when the frequency of the crystal piece 21 is 9.2 MHz. The crystal piece 21 is formed in a circular shape, and its diameter D is 8.7 mm. Therefore, the crystal piece 21 has a ratio of the diameter D of the crystal 21 to the thickness t of the crystal piece 21, that is, the value of the side ratio D / t is 47.802.

  Further, one excitation electrode 22 and the other excitation electrode 23 formed in a circular shape having a diameter d smaller than that of the crystal piece 21 of 7.0 mm are attached to one side and the other side of the crystal piece 21, respectively. The ratio of the area of the excitation electrodes 22 and 23 to the area of the crystal piece 21 is 65.7%. In this way, by setting the area ratio to 65.7%, high measurement accuracy is secured, and a surface on which the annular protrusion 41 is pressed in the crystal piece 21 is secured as will be described later. Here, when the area ratio is 70% or more, the annular protrusion 41 approaches or comes into contact with the formation area of the excitation electrode 22 on one surface side of the crystal piece 21, thereby causing unnecessary vibrations and variations in the CI values between the crystal sensors 20. Therefore, the area ratio is preferably 60 to 70%.

  In this embodiment, in the quartz sensor 20 using the Langevin type 9.2 MHz quartz crystal resonator 2, in order to reduce the size and ensure high sensitivity, the thickness t of the quartz piece 21 as described above is secured. The ratio of the diameter D of the crystal 21 is 47.802, and the ratio of the area of the excitation electrodes 22 and 23 to the area of the crystal piece 21 is 65.7%. Then, the extraction electrodes 24 and 25 are formed on the crystal piece 21 set in this way.

  One end side of one strip-shaped extraction electrode 24 is connected to the one excitation electrode 22 on one surface side of the crystal piece 21, and the extraction electrode 24 is bent along the end surface of the crystal piece 21, The crystal piece 21 is turned to the other surface side. Further, on the other surface side of the crystal piece 21, one end side of the other strip-like extraction electrode 25 is formed by being connected to the other excitation electrode 22 in the same layout as the one extraction electrode 24. The layout of the excitation electrode 22 (23) and the extraction electrode 24 (25) is the same on both sides. The lateral width r of the extraction electrodes 24 and 25 is 1.5 mm. The lateral width r of the extraction electrodes 24 and 25 is determined based on the diameter d of the excitation electrodes 22 and 23. Specifically, in the excitation electrodes 22 and 23 in which the diameter d is determined, the diameter d of the excitation electrodes 22 and 23 is determined. The lateral width r of the extraction electrodes 24 and 25 is determined so that the size of the lateral width r of the extraction electrodes 24 and 25 is 0.3 or less. The lower limit value of the lateral width r of the extraction electrodes 24 and 25 only needs to be large enough to maintain electrical continuity in the extraction electrodes 24 and 25. The excitation electrodes 22 and 23 and the extraction electrodes 24 and 25 have a thickness W of, for example, 2000 mm, and the electrode material is, for example, gold (Au).

  In the present embodiment, the following characteristics can be obtained by configuring the crystal resonator 2 used in the crystal sensor 20 as described above. As shown in FIG. 3A, the main vibration of the crystal resonator 2 is less likely to leak from the excitation electrodes 22 and 23 to the extraction electrodes 24 and 25, and the vibration energy is concentrated at the center of the crystal piece 21. On the other hand, the crystal resonator 10 used in the conventional crystal sensor is shown in FIG. 3B because the line width of the extraction electrode is larger than the line width of the extraction electrodes 24 and 25 of the crystal resonator 2 described above. Thus, the vibration energy of the thickness-shear mode that is the main vibration does not sufficiently concentrate on the center portion of the crystal piece 12 and reaches the end portion of the crystal piece 12. That is, by reducing the line width of the extraction electrodes 24 and 25, the amount of vibration leakage from the center to the end of the crystal piece 21 is reduced.

  As will be described later, since the excitation electrode 22 is provided facing the liquid storage space 45 to which the sample liquid is supplied, an adsorption layer (not shown) in which an antibody adheres to the surface is provided on the excitation electrode 22. . This antibody is selectively adsorbed by an antigen-antigen reaction with an antigen that is a measurement object, for example, dioxin. When the measurement object is adsorbed to the adsorption layer, the antibody depends on the amount of adsorption of the measurement object. The frequency of the crystal piece 21 changes.

  Next, the wiring board 3 will be described. As shown in FIG. 5, the wiring board 3 is composed of, for example, a printed circuit board, and electrodes 31 and 32 are provided at intervals from the front end side to the rear end side of the surface. A through-hole 33 is formed between the electrodes 31 and 32 so as to have a thickness walk of the wiring board 3. As will be described later, the through-hole 33 constitutes a recess that forms an airtight space where the excitation electrode 23 on the back surface side of the crystal resonator 2 faces, and the diameter of the through-hole 33 is formed so as to accommodate the excitation electrode 23. Yes.

  Further, two parallel line-shaped conductive path patterns are formed as connection terminal portions 34 and 35, respectively, closer to the rear end side than the portion where the electrode 32 is formed. One connection terminal portion 34 is electrically connected to the electrode 31 via the pattern 34a, and the other connection terminal portion 35 is electrically connected to the electrode 32 via the pattern 35a. In FIG. 1, for convenience of illustration, each electrode and pattern of the substrate 3 are omitted.

  Reference numeral 36 in FIG. 5 denotes a weir formed by photolithography using a resist, for example, and is formed along the outer shape of the crystal unit 2. The weir 36 serves to align the crystal resonator 2, and the crystal resonator 2 is placed in a region surrounded by the weir 36. In FIG. 5, 37 a, 37 b, 37 c are engagement holes, which are drilled in the thickness direction of the wiring board 3. These engagement holes 37a, 37b, and 37c are engaged with engagement protrusions 51a, 51b, and 51c provided on the lower surface of the cover 5, respectively. Further, reference numerals 38 a, 38 b, and 38 c in FIG. 5 are notches formed on the peripheral edge of the wiring board 3. Further, claw portions 52a, 52b, and 52c bent inward are provided on the peripheral edge portion of the lower surface of the cover 5, and the notches 38a, 38b, and 38c are engaged with the claw portions 52a, 52b, and 52c, respectively. .

  The sealing member 3 </ b> A is a film-like member and constitutes a concave portion that forms an airtight space together with the through-hole 33.

  Next, the crystal pressing member 4 will be described. The crystal pressing member 4 is made of, for example, silicon rubber, and has a shape corresponding to the wiring board 3. More specifically, the crystal pressing member 4 is formed in a plate shape having rectangular cutout portions 41a, 41b, and 41c respectively corresponding to the cutout portions 38a, 38b, and 38c as shown in FIG. Has been. Further, when the side where the notches 41 b and 41 c are formed is the rear side, the notch 41 a is formed at the center of one edge on the front side of the crystal pressing member 4.

  FIG. 6 is a perspective view showing the lower surface side of the crystal pressing member 4, and the configuration of the pressing member 4 will be described with reference to this drawing. As shown in FIGS. 1 and 6, a recess 42 for accommodating the crystal resonator 2 is formed on the lower surface of the crystal pressing member 4. An annular protrusion 43 that is slightly larger than the through-hole 33 on the upper surface of the wiring board 3 is provided at the center of the ceiling surface portion (bottom surface portion in the case of description in the direction of FIG. 6) of the recess 42. The annular protrusion 43 has a role of pressing the crystal unit 2 against the region surrounding the through-hole 33 and fixing the position of the crystal unit 2.

  As shown in FIGS. 1, 5, and 6, an opening 44 is formed on the surface side of the crystal pressing member 4, and the opening 44 communicates with a space surrounded by the annular protrusion 43. .

  The peripheral surface 44a of the opening 44 and the inner peripheral surface 43a of the annular protrusion 43 are inclined inward and downward. That is, the diameters of the opening 44 and the annular protrusion 43 become smaller as it goes downward. The tip 47 of the annular protrusion 43 presses the peripheral edge of the crystal piece 20. A region surrounded by the peripheral surfaces 43a and 44a and the crystal resonator 2 constitutes a liquid storage space 45 for storing the sample liquid.

  Further, 46a and 46b in FIG. 5 are engagement holes that are perforated so as to penetrate the pressing member 4 in the thickness direction, and the engagement holes 37a and 37b of the wiring board 3 and the liquid injection cover 5 are engaged. It is formed so as to correspond to the protrusions 51a and 51b. In FIG. 5, 46 c is an arc-shaped cutout formed at the center of the rear edge, and corresponds to the engagement hole 37 c of the wiring board 3 and the engagement protrusion 51 c of the liquid injection cover 5.

  Next, the configuration of the liquid injection cover 5 will be described. The cover 5 is made of, for example, polycarbonate, and a sample liquid injection port 53 and a confirmation port 54 are formed on the front side and the back side of the upper surface, respectively. As shown in FIG. 1, an injection path 55 that is a groove is formed in the lower surface of the cover 5 along the length direction of the cover 5, and one end and the other end of the injection path 55 are an injection port 53 and a confirmation port. 54, respectively. The injection path 55 is provided so as to face the opening 44, and the sample liquid injected into the injection port 53 is supplied to the liquid storage space 45 through the injection path 55. When a predetermined amount of sample liquid is supplied to the crystal sensor 20, the liquid level of the sample liquid appears at the confirmation port 54, and it is possible to check whether or not the liquid is supplied to the sensor 20.

  An annular weir 56 surrounding the injection path 55 is provided on the lower surface of the cover 5, and the weir 56 is recessed into the crystal pressing member 4 so that the sample liquid injected into the injection port 51 is pressed against the liquid injection cover 5. It has a role of preventing leakage from between the members 4.

  The crystal sensor 20 is assembled as follows. First, the through hole 33 of the wiring board 3 is closed by the sealing member 3 </ b> A, and a recess is formed in the board 3. Subsequently, the crystal resonator 2 is placed so that the extraction electrodes 24 and 25 on the crystal resonator 2 side overlap with the electrodes 31 and 32 on the wiring substrate 3 side, and the excitation electrode 23 on the back surface side of the crystal resonator 2 overlaps the concave portion. Placed on the wiring board 3.

  Next, the engagement protrusions 51a to 51c of the liquid injection cover 5 are engaged with the engagement holes 46a and 46b and the notch 46c of the crystal pressing member 4, and the liquid injection cover 5 and the pressing member 4 are overlapped. Thereafter, the claws 52 a, 52 b, 52 c of the liquid injection cover 5 and the notches 38 a, 38 b, 38 c of the wiring board 3 are put on each other so as to be fitted and pressed toward the wiring board 3. Thereby, each claw part 52a-52c of the cover 5 for liquid injection is bent to the outer side of the wiring board 3, and also each claw part 52a-52c is the lower surface of the peripheral part of the wiring board 3 via each notch part 38a-38c. At the same time, the claw portions 52a to 52c are restored to their original shape by the inward restoring force, and the wiring board 3 is sandwiched between the claw portions 52a to 52c and locked together. The pressing member 4 sandwiched between the substrate 3 and the cover 5 is pressed against them.

  Due to the elasticity of the pressed pressing member 4, the annular protrusion 43 presses the outer portion of the recess on the surface of the crystal resonator 2 toward the wiring substrate 3, thereby fixing the position of the crystal resonator 2. The peripheral edge is in close contact with the wiring board 3, and the concave portion formed by the through hole 33 and the sealing member 3 </ b> A becomes an airtight space, and the excitation electrode 23 on the back side of the crystal unit 2 faces this airtight space, and the crystal The lead electrodes 24 and 25 on the vibrator 2 side are in close contact with the electrodes 31 and 32 on the wiring board 3 side, and the crystal vibrator 2 and the wiring board 3 are electrically connected.

  When the crystal sensor 20 in the present embodiment is used, an operator injects the sample liquid into the injection port 53 of the liquid injection cover 5 by using, for example, an injector. The sample liquid injected into the injection port 53 is supplied to the liquid storage space 45 of the sample liquid constituted by the opening 44 and the annular protrusion 43, and the excitation electrode 22 on the surface side of the crystal resonator 2 is in contact with the sample liquid. The antibody in the sample solution is adsorbed by the antigen-antibody reaction on the adsorption layer formed on the surface of the excitation electrode 22. The natural frequency of the crystal unit 2 is reduced according to the amount of adsorption. As a result, the difference between the natural frequency of the crystal unit 2 before the antigen is adsorbed on the adsorption layer and the natural frequency of the crystal unit 2 after the antigen is adsorbed on the adsorption layer, that is, the amount of change is obtained.

  According to the present invention, in a crystal sensor 20 using a crystal resonator 2 of Langevin type of 9 MHz or less, in order to reduce the size and secure high sensitivity, the side ratio is 50 or less and the area ratio is 50%. That must be done. However, with such a configuration, as shown in FIG. 3B, the ratio of vibration leaking from the excitation electrodes 22 and 23 to the extraction electrodes 24 and 25 increases. Therefore, the area ratio is set to 70% at most and the size of the lateral width r of the extraction electrodes 24 and 25 is set to 0.3 or less of the size of the diameter d of the excitation electrodes 22 and 23, so that FIG. As shown, the main vibration of the vibrator is less likely to leak from the excitation electrodes 22 and 23 to the extraction electrodes 24 and 25, and the vibration energy is concentrated at the center of the crystal piece 21. For this reason, even if there is a variation in the stress applied to the crystal piece 21 by the annular protrusion 43 of the holding member 4 between the quartz sensors 20, the variation in the vibration mode is suppressed. As shown in the embodiments described later, the crystal impedance ( CI) Variation in value is suppressed.

  In the crystal sensor 20, the crystal pressing member 4 may be formed of an elastic body other than rubber.

  In the above, the present invention relates to, for example, a crystal sensor maker in which an antibody concentration of a solution containing an antibody and an amount of change in the vibration frequency of the crystal resonator (antibody adhesion amount) However, the present invention can also be applied to a quartz sensor for performing such verification. Accordingly, “detecting a measurement object in a sample solution” in the claims includes an act of measuring a change in the vibration frequency of the crystal resonator by attaching an antibody to the electrode surface of the crystal resonator.

  The above-described quartz sensor 20 is used as a detection unit of the sensing device by being connected to the measuring instrument body 6 having a configuration as shown in FIG. 7 which is a block diagram, for example. In FIG. 7, 62 is an oscillation circuit for oscillating the crystal piece 21 of the crystal sensor 20, 63 is a reference clock generator for generating a reference frequency signal, and 64 is a frequency difference detecting means comprising a heterodyne detector, for example. Based on the frequency signal from 62 and the clock signal from the reference clock generator 63, a frequency signal corresponding to the frequency difference between the two is extracted. 65 is an amplifying unit, 66 is a counter that counts the frequency of an output signal from the amplifying unit 65, and 67 is a data processing unit.

  Since the frequency of the quartz sensor 20 is 9.2 MHz, for example, 10 MHz is selected as the frequency of the reference clock generator 63. When the object to be measured, for example, dioxin is not adsorbed to the above-described adsorption layer provided on the quartz crystal resonator 2 of the quartz sensor 20, the frequency difference detecting means 64 determines the difference between the frequency from the quartz sensor side and the frequency of the reference clock. 1 MHz frequency signal (frequency difference signal) is output, but when the measurement object contained in the sample solution is adsorbed to the adsorption layer of the crystal resonator 2, the natural frequency of the crystal resonator 2 changes, and this Therefore, since the frequency difference signal also changes, the count value in the counter 66 changes, and thus the concentration of the measurement object or the presence or absence of the substance can be detected.

  An experiment conducted for confirming the effect of the present invention will be described.

(Example)
In the structure of the crystal sensor 20 shown in FIG. 1 described above, the diameter D of the crystal piece 21 is 182 μm, the thickness t is 8.7 mm, the diameter d of the excitation electrodes 22 and 23 is 7.0 mm, and the extraction electrodes 24 and 25 The lateral width r was 1.5 mm, the thicknesses of the excitation electrodes 22 and 23 and the extraction electrodes 24 and 25 were 2000 mm, and 1235 crystal sensors 20 were produced. The crystal impedance (CI) value of the main vibration of these crystal sensors 20 was measured. The result is shown in FIG. The vertical axis in FIG. 8 is the number of crystal sensors 20, and the horizontal axis is the CI value.
(Comparative example)
Twenty quartz sensors 20 were produced in the same manner as in the example except that the lateral width r of the extraction electrodes 24 and 25 was 2.5 mm. With respect to these crystal sensors 2, crystal impedance (CI) values of main vibrations were measured. The result is shown in FIG. The vertical axis in FIG. 9 is the number of crystal sensors 20, and the horizontal axis is the CI value.
(Results and discussion)
As shown in FIG. 9, in the comparative example, the vibration energy in the thickness-sliding mode, which is the main vibration, does not sufficiently concentrate on the center portion of the crystal piece 21 and reaches the end portion of the crystal piece 21. It can be seen that the crystal impedance (CI) value varies between the quartz sensors 20. More specifically, there are 85 crystal sensors 20 with a CI value of 7Ω, 25 crystal sensors 20 with a CI value of 9Ω, and 10 crystal sensors 20 with a CI value of 11Ω, and a CI value of 11Ω to 21Ω. Then, there are dozens of quartz sensors 20.

  On the other hand, as shown in FIG. 8, in the embodiment, the size of the lateral width r of the extraction electrodes 24, 25 is set to 0.3 or less of the size of the diameter d of the excitation electrodes 22, 23. The main vibration is less likely to leak from the excitation electrodes 22 and 23 to the extraction electrodes 24 and 25, and the vibration energy is concentrated at the center of the crystal piece 21 so that variations in vibration modes are suppressed, and variations in CI values between the crystal sensors 20 occur. You can see that it is suppressed. More specifically, 800 crystal sensors 20 with a CI value of 5Ω, 400 crystal sensors 20 with a CI value of 7Ω, 20 crystal sensors 20 with a CI value of 9Ω, and a crystal sensor 20 with a CI value of 11Ω. The crystal sensor 20 hardly exists when the CI value is 12Ω to 21Ω.

  In this embodiment, the ratio of the area of the excitation electrodes 22 and 23 to the area of the crystal piece 21 is 65.7%, but the diameter d of the excitation electrodes 22 and 23 is 7.3 mm and the area ratio is 70%. In addition, as described above, it has been confirmed that the variation of the CI value among the crystal sensors 20 can be suppressed. When the diameter d of the excitation electrodes 22 and 23 is 7.4 mm and the area ratio is 72%, the annular protrusion 41 approaches the formation area of the excitation electrode 22 on one side of the crystal piece 21 as described above. As a result, unnecessary vibrations occurred, and CI values varied among the quartz sensors 20.

It is a vertical side view of the crystal sensor which concerns on embodiment of this invention. It is the top view and sectional drawing which showed the structure of the crystal piece which concerns on embodiment of this invention. It is explanatory drawing which shows distribution of the vibration energy of the thickness shear mode which is the main vibration in the plane of a crystal piece. It is a perspective view of the crystal sensor. It is a disassembled perspective view of the crystal sensor. It is a perspective view of the back surface side of the crystal pressing member which comprises the said crystal sensor. It is a block diagram of the sensing apparatus containing the said quartz sensor. It is explanatory drawing which shows the experimental result performed in order to confirm the effect of this invention. It is explanatory drawing which shows the experimental result performed in order to confirm the effect of this invention. It is a schematic vertical side view which shows the principal part of the conventional quartz sensor.

Explanation of symbols

20 Crystal sensor 2 Crystal oscillator 21 Crystal piece 22, 23 Excitation electrode 24, 25 Extraction electrode 3 Wiring board 4 Crystal holding member 43 Annular projection 44 Opening 45 Liquid storage space 5 Liquid injection cover 6 Measuring instrument body

Claims (3)

In the piezoelectric sensor that is electrically connected to the measuring instrument body to detect the measurement object in the sample liquid,
A wiring board provided with a connection terminal part connected to the measuring instrument main body, and on one side thereof, an electrode electrically connected to the connection terminal part and a recess for constituting an airtight space;
A circular excitation electrode is provided on one surface side and the other surface side of the circular piezoelectric piece, and a strip-shaped extraction electrode is provided from the excitation electrode and electrically connected to the electrode. The excitation electrode on the side is provided on the wiring board so as to face the recess, and the ratio of the diameter of the piezoelectric piece to the thickness of the piezoelectric piece is 50 or less, and the frequency of the main vibration is 9 MHz or less. A piezoelectric vibrator;
A liquid storage space having a bottom surface on one surface side of the piezoelectric vibrator is formed, and is provided so as to surround the liquid storage space. The piezoelectric resonator is formed by pressing an outer portion of the concave portion on the one surface side of the piezoelectric vibrator toward the wiring board side. A holding member made of an elastic material having an annular protrusion for fixing the position of the vibrator;
A liquid injection cover that covers the pressing member facing the wiring substrate, communicates with the liquid storage space on the surface thereof, and is provided with an injection port for injecting a sample liquid into the liquid storage space. ,
The ratio of the area of the excitation electrode to the piezoelectric piece is 60 to 70%, and the width of the extraction electrode is set to 0.3 or less of the diameter of the excitation electrode. .   The piezoelectric vibrator includes an excitation electrode provided on one surface side of the piezoelectric piece, and an adsorption layer formed on the surface of the excitation electrode for adsorbing the sensing object, and is inherent to the sensing object by adsorption. 2. The piezoelectric sensor according to claim 1, wherein the frequency changes.   The piezoelectric sensor according to claim 1, and a measuring device main body that detects a natural frequency of the piezoelectric vibrator and detects a measurement object in the sample liquid based on the detection result. Sensing device.

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