JP2013024562A - Mass measuring method and mass measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mass measuring method which can accurately measure the mass of a droplet or a solid in the droplet dripped by an ink jet system, and a mass measuring apparatus.SOLUTION: In a mass measuring method, a droplet to be measured is dripped from an IJ head (12) to a crystal oscillator (14) that is oscillated, resonance frequencies F, Fbefore and after depositing the droplet to be measured to the crystal oscillator are measured and the mass of the droplet or a solid contained in the droplet is calculated on the basis of a difference of F, F. Total volume V of droplets to be measured represented with a surface area Aof an electrode (42) of the crystal oscillator, a resonance frequency F in the case where no droplet is deposited, viscosity η of the droplet and a density ρ of the droplet satisfies V≤A×{η/(π×ρ×F)}. After droplets to be measured are not matched and the preceding droplet reaches an equilibrium state, the next droplet is dripped, and the resonance frequency Fbefore depositing the droplet to be measured is measured. After the preceding droplet reaches the equilibrium state, the resonance frequency Fafter depositing that droplet is measured.

Description

  The present invention relates to a mass measuring method and a mass measuring device, and more particularly to a technique for measuring a minute mass such as a mass of a solid substance in a droplet and a mass of a droplet with high accuracy.

  In recent years, inkjet technology is sometimes used in industrial applications such as pattern formation using functional liquids. When the ink jet technology is used for industrial applications, a predetermined pattern is formed microscopically in order to develop functionality, so it is necessary to measure the mass of each droplet and to grasp discharge variation. However, a technique for accurately and accurately measuring the mass of a nanogram-scale minute droplet formed by an inkjet method has not been established.

  As a method for measuring a minute mass change on the nanogram scale, Non-Patent Document 1 discloses a quartz crystal chemical measurement system. In such a technique, a crystal resonator is resonated, a substance having a nanogram-scale minute mass is attached to the crystal resonator, and the minute mass is grasped from a change in the resonance frequency of the crystal resonator.

  The method for measuring a minute mass described in Non-Patent Document 1 is also called a quartz crystal microbalance (QCM) method, and is the same as the method for measuring a minute mass described in Non-Patent Document 1. The technique is also disclosed in Patent Documents 1 to 5 below.

  Patent Document 1 discloses an ink jet printer that ejects ink from a head to a vibrator, detects a change in the resonance frequency of the vibrator, and grasps the mass of ink attached to the vibrator from the detection result.

  Patent Document 2 discloses a droplet weight measuring method for detecting a resonance frequency of a piezoelectric vibrator before and after a droplet is discharged and measuring the weight of the droplet based on the resonance frequency.

  Patent Document 3 discloses an ink jet coating apparatus including an ink coating amount measuring device that outputs correction information for correcting the ejection operation of an ink ejection mechanism based on a change in frequency caused by a droplet landing on a crystal resonator. Disclosure.

  Patent Document 4 discloses a droplet discharge amount evaluation test apparatus including a crystal resonator and a measuring device that measures the weight of the droplet based on a change in the resonance frequency of the crystal resonator.

  Patent Document 5 discloses a liquid in which a plurality of droplets are arranged on the surface of an electrode of a vibrator, and the mass of the plurality of liquid droplets is determined based on the result of detecting the frequency of the vibrator in the drying process of the plurality of liquid droplets. A method for measuring drop information is disclosed.

Ultrasonic Techno (Nihon Kogyo Shuppan) February 1995 issue, special issue: “Crystal Crystal Chemistry Measurement System” for Measuring Viscosity by Vibration, Hiroshi Matsumura, Tatsuaki Anya

JP 2003-305831 A JP 2005-61869 A JP 2005-262450 A JP 2004-361234 A JP 2005-28277 A

  However, Non-Patent Document 1 and Patent Document 1 to Patent Document 5 disclose that it is possible to measure the mass of a minute amount of droplets or measure the evaporation amount of a minute amount of droplets. And the concrete structure (form) is not disclosed.

  The present invention has been made in view of such circumstances, and provides a mass measuring method and a mass measuring apparatus capable of accurately measuring the mass of a droplet to be ejected by an inkjet method or a solid matter in the droplet. With the goal.

In order to achieve the above object, a mass measurement method according to the present invention includes a droplet attachment step of attaching a droplet to be measured to an oscillated vibrator, and a method of measuring the measurement object to the oscillated vibrator. with measuring the resonant frequencies F ₁ of the vibrator before the deposition of droplets, the frequency measurement step of measuring the resonant frequency F ₂ of the vibrator after deposition of the droplets of the measurement object, the measurement on the basis of the difference between the resonant frequency F ₂ of the oscillator after said depositing the droplets of the measurement target and the resonant frequencies F ₁ of the vibrator before the depositing the droplets of the measurement object is, the A calculation step of calculating a mass of a droplet attached to the vibrator or a mass of a solid substance contained in the droplet attached to the vibrator, wherein the droplet attachment step is a measurement target of the vibrator adhering surface area a _Q, a droplet surface to deposit the droplets of The total amount V of the liquid droplets to be measured attached to the vibrator, which is expressed using the resonance frequency F when the liquid crystal is not used, the viscosity η of the liquid droplets to be measured, and the density ρ of the liquid droplets to be measured is V ≦ A _Q × {η / (π × ρ _L × F)} ^1/2 is satisfied, and at least one droplet to be measured is attached to each of a plurality of attachment positions of the vibrator. Then, after satisfying the condition that the droplets to be measured attached at different attachment positions do not coalesce and the droplet to be measured previously attached reaches an equilibrium state on the vibrator, the next liquid A droplet to be measured next is attached to a position where the droplet is attached, and the frequency measurement step includes a resonance before attaching the droplet to be measured to the vibrator for each of a plurality of attachment positions of the vibrator. the frequencies F ₁ measured droplets of the object to be measured is attached to the vibrator After reaching衡state, and measuring the resonant frequency F ₂ of the vibrator after deposition of the droplets of the measurement target.

According to the present invention, the vibrator is adjusted so that the total amount of droplets to be measured attached to the vibrator represented by V ≦ A _Q × {η / (π × ρ _L × F)} ^1/2 is less than the total amount. The liquid droplets to be measured are attached, satisfying the condition that the liquids attached to different attachment positions do not coalesce, and after the previously attached liquid droplets have reached an equilibrium state, the next liquid droplet is applied to the next attachment position. The droplet to be measured is attached so that the condition for attachment is satisfied, and the resonance frequency of the vibrator after the droplet to be measured reaches the equilibrium state is measured as the resonance frequency of the vibrator after the droplet is attached. Therefore, the resonance frequency of the vibrator after the droplet is attached is accurately measured, and the mass of the droplet to be measured is accurately obtained.

1 is an overall configuration diagram showing a schematic configuration of a droplet mass measuring apparatus (system) according to an embodiment of the present invention. FIG. 1 is a plan view showing the configuration of the crystal unit shown in FIG. Equivalent circuit diagram of the crystal unit shown in FIG. Explanatory drawing of the measurement principle of the frequency measurement unit shown in FIG. 1 is a block diagram illustrating an example of the oscillation circuit illustrated in FIG. The figure explaining the result of the resonant frequency measurement in the frequency measurement part shown in FIG. Explanatory drawing schematically showing a plurality of droplets that are in equilibrium without being united on the crystal unit The figure which shows the result of the resonant frequency measurement of the some droplet shown in FIG. Partial enlarged view of FIG. Explanatory drawing that schematically illustrates a united droplet on a crystal unit The figure which shows the result of the resonant frequency measurement of the droplet shown in FIG. Partial enlarged view of FIG. Illustration of contact angle of droplet Explanatory drawing which shows the change with time passage of the contact angle and the diameter of the droplet in the extended wet state The figure which shows the result of resonance frequency measurement of non-volatile liquid Partial enlarged view of FIG. The flowchart which shows the flow of control of the frequency measurement by a frequency measurement part when a several droplet is ejected from the same nozzle. The flowchart which shows the flow of control of the frequency measurement by a frequency measurement part when a droplet is ejected from a different nozzle.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Overall configuration of mass measuring device (system)]
FIG. 1 is an overall configuration diagram showing a schematic configuration of a mass measuring apparatus (system) according to an embodiment of the present invention. The mass measurement apparatus shown below measures the mass of a droplet ejected from an inkjet head accurately and with high accuracy using a quartz crystal microbalance (QCM) method.

  A mass measuring device 10 shown in FIG. 1 supports a crystal resonator 14 to which a droplet to be measured ejected from an inkjet head 12 is attached, and a side surface opposite to the surface of the crystal resonator 14 facing the inkjet head 12. Based on the measurement result of the support unit 15, the oscillation circuit 16 that oscillates the crystal unit 14, the frequency measurement unit 18 that measures the resonance frequency of the crystal unit 14, and the frequency measurement unit 18, And a mass calculation unit 20 that calculates the mass of the droplet.

  In the ink jet head 12, droplet ejection is controlled by the droplet ejection controller 22. The droplet ejection control unit 22 applies a driving voltage to the inkjet head 12, selects a nozzle for ejecting droplets, and commands the droplet ejection amount and droplet ejection timing of the nozzle.

  Although detailed illustration of the structure of the inkjet head 12 is omitted, there are various methods such as a piezoelectric method including a piezoelectric element as a pressure generating element, and a thermal method including a heater for heating a droplet and utilizing a film boiling phenomenon of the droplet. The droplet ejection method can be applied.

  The inkjet head 12 is supported by a moving unit 24 so as to be movable in a plane parallel to the droplet landing surface 14A of the crystal resonator 14. By moving the ink-jet head 12, the landing position of the droplet on the droplet landing surface 14A of the crystal resonator 14 can be changed as appropriate. The arrow line illustrated in FIG. 1 represents the moving direction of the inkjet head 12.

  Although not shown, a plurality of nozzles are provided on the nozzle surface of the ink jet head 12 (the surface facing the crystal resonator 14). Examples of the nozzle arrangement of the inkjet head 12 include a single-line arrangement, a two-row staggered arrangement, and a matrix arrangement.

  Although detailed illustration of the moving unit 24 is omitted, the moving unit 24 includes a guide that supports the inkjet head 12, a drive mechanism such as a ball screw and a belt drive system, and a drive source (motor) of the drive mechanism. Note that a linear actuator in which a drive mechanism and a drive source are integrated may be applied.

  The head movement control unit 26 controls the movement of the inkjet head 12 by operating the driving source. The head movement control unit 26 includes a drive circuit (driver circuit) that supplies electric power to the drive source and a command signal generation unit that generates a command signal to be sent to the drive circuit.

  The measurement data of the resonance frequency of the crystal resonator 14 measured by the frequency measurement unit (frequency counter) 18 is stored in the storage unit 30 via the system control unit 28. Further, the measurement data is sent to the mass calculation unit 20 via the system control unit 28, and the mass calculation unit 20 performs a calculation based on the measurement data to calculate the mass of the droplet to be measured.

  Note that the frequency measurement unit 18 and the storage unit 30 may be integrated. Further, the mass data calculated by the mass calculation unit 20 may be stored in the storage unit 30, or a storage unit that stores the mass data accompanying the mass calculation unit 20 may be provided.

  FIG. 2 is a plan view showing the configuration of the crystal resonator 14 shown in FIG. As shown in FIG. 2, the crystal resonator 14 includes a crystal piece 40 having a square planar shape, and the front surface (the surface shown in the figure) and the back surface (the opposite surface of the surface shown in the figure) of the crystal piece 40. ) Is provided with a pair of electrodes 42 and 44. The electrode 42 in the figure is provided on the front surface in the figure, and the electrode 44 is provided on the back surface in the figure.

  That is, the crystal resonator 14 has a structure in which the crystal piece 40 is sandwiched between the pair of electrodes 42 and 44. The electrodes 42 and 44 are metals having high conductivity such as gold (Au), platinum (Pt), and chromium (Cr), and are preferably metals having a predetermined liquid resistance that does not corrode from the liquid droplets to be measured.

  The crystal piece 40 is supported by the L-shaped support members 46 and 48 so as to be able to vibrate, and is fixed to the insulator 50 while being supported by the support members 46 and 48. The supports 46 and 48 are conductive, the electrode 42 is electrically connected to the support 46, and the electrode 44 is electrically connected to the support 48. Further, the support body 46 is electrically connected to the terminal 52, and the support body 48 is electrically connected to the terminal 54.

  One of the terminals 52 and 54 in FIG. 2 is connected to an oscillation circuit (see FIG. 1) for oscillating the crystal resonator 14, and the other is connected to the frequency measuring unit 18.

FIG. 3 is an equivalent circuit diagram of the crystal unit 14. The crystal resonator 14 is electrically equivalent to an electric circuit in which a capacitor C ₀ is connected in parallel to a series connection circuit of an inductive component L ₁ , a capacitance component C _1, and a resistance component R ₁ .

The capacitor C ₀ is a capacitance component (electrical parallel capacitance) due to the electrodes 42 and 44 provided on both surfaces of the crystal piece 40, and the inductive component L ₁ , the capacitance component C ₁ , and the resistance component R ₁ are subjected to electrical vibration. Corresponding factors, which are associated with mechanical vibrations.

That is, the induction component L ₁ corresponds to mass, the capacitance component C ₁ corresponds to a spring constant, and the resistance component R ₁ corresponds to mechanical resistance.

  Further, the crystal piece 40 has an electric natural frequency. When the electrode 42 (44) provided on both sides of the crystal piece 40 is energized, the LRC resonance circuit (equivalent circuit) oscillates at the natural frequency. Starting, the crystal piece 40 also vibrates at the same frequency as the oscillation frequency.

  The oscillation frequency (natural frequency) of the crystal piece 40 is mainly determined by the angle at which the crystal piece 40 is cut out with respect to the crystal growth axis and the thickness of the crystal piece 40. The vibration form of the crystal piece 40 is determined by the angle at which the thin plate is cut out. In the QCM, a crystal cut out at a predetermined angle called AT cut, which easily generates mechanical harmonic vibration (overtone), is applied.

  The vibration mode of the AT-cut crystal piece 40 is so-called thickness-shear vibration, in which the front and back surfaces of the crystal piece 40 vibrate so as to deviate from each other in a direction orthogonal to the thickness direction of the crystal.

  If the external force acting on the crystal unit 14 is constant, the crystal unit 14 vibrates at a constant resonance frequency. However, when the external force changes due to the liquid droplets adhering to the electrode 42 (44), the crystal unit 14 depends on the amount of change in the external force. The resonance frequency changes.

  That is, when a droplet adheres to either one of the electrodes 42 and 44 that sandwich the crystal piece 40, the resonance frequency of the crystal resonator 14 changes according to the mass and viscosity of the adhered droplet.

FIG. 4 is a block diagram showing an example of the configuration of the frequency measurement unit 18 shown in FIG. 1, and shows a schematic configuration of a measurement circuit using an external oscillation method. As shown in FIG. 4, to connect the oscillator 16 to one electrode 42 of the crystal resonator 14, exciting the crystal oscillator 14 by applying an oscillating voltage V _in.

Voltmeter 60 measures the voltage across V _p of which is connected between the other electrode 44 of the quartz resonator 14 is excited GND resistor R _L. A current flowing from the measurement voltage V _{p of the} voltmeter 60 to the resistor _RL , that is, a current I _p (= V _p / R _L ) flowing to the crystal resonator 14 is grasped.

The electrical impedance (= V _in / I _p ) of the crystal resonator 14 with respect to the frequency is obtained from the relationship between the vibration voltage V _in applied to the crystal resonator 14 and the current I _p flowing through the crystal resonator 14. It is done. Since the impedance changes greatly near the resonance frequency, the resonance frequency can be grasped from the change in impedance.

  In addition to the external oscillation method shown in FIG. 4, it is also possible to measure the admittance characteristics of the crystal resonator 14 and obtain the resonance frequency by using an impedance analyzer or a network analyzer.

The resonance frequency itself changes due to the change in the mass of the droplet to be measured, which is reflected in the induction component L ₁ (see FIG. 3) of the equivalent resonance circuit, but it is preferable to consider the influence of the viscosity of the droplet.

  FIG. 5 is a block diagram showing a specific example of the oscillation circuit 16 shown in FIG. The oscillation circuit shown in the figure is a high-frequency oscillation circuit called PLL (Phase Lock Loop), and uses resonance circuits 74 and 76 that cause amplifiers 70 and 72 to resonate by applying positive feedback.

  The oscillation circuit 16 including the crystal resonator 14 shown in FIG. 5 is in a resonance state, and the frequency measurement unit 18 measures the resonance frequency that changes when a droplet adheres to the electrode 42 (44) of the crystal resonator 14. be able to.

The mass calculation unit 20 measures the resonance frequency F ₁ (Hertz) before the droplet is attached to the crystal resonator 14 measured by the frequency measurement unit 18 and the resonance frequency F ₂ (Hertz) after the droplet is attached. From the change ΔF (F ₂ −F ₁ ) (Hertz), the mass m of the droplet to be measured is calculated.

Here, the relationship between the change ΔF of the resonance frequency and the mass m (gram) of the droplet is expressed by the following equation: ΔF = −2 × F ₀ ² × {m / (A _E × (ρ × μ) ^1/2 ) }
It is represented by

F ₀ is the fundamental frequency (Hertz), μ is the elastic modulus of the crystal piece 40 (dyne per square centimeter), ρ is the density of the crystal piece 40 (gram per cubic centimeter), and A _E is the total area of the electrode 42 (44) ( Square centimeter).

The elastic modulus μ of the AT-cut crystal piece 40 is 2.95 × 10 ¹⁵ (dyne per square centimeter), and the density ρ of the crystal (quartz single crystal) is 2.6 (gram per cubic centimeter).

Further, the relationship between the fundamental frequency F ₀ and the thickness t (millimeter) of the crystal piece 40 is expressed by the following formula: F ₀ = K / t
It is represented by Note that K (megahertz · millimeter) is a constant determined by the cut surface of the crystal piece 40, and is 1.66 megahertz · millimeter in the case of AT cut.

[Specific example of frequency (mass) measurement]
Next, a specific example of mass measurement will be described. FIG. 6 shows measurement data of the resonance frequency of the crystal resonator 14 obtained by the frequency measurement unit 18 and shows a change in the resonance frequency with time. The horizontal axis in FIG. 6 is elapsed time (seconds), and the vertical axis is frequency (hertz).

  As an inkjet head system, DMP-2831 (manufactured by FUJIFILM Dimatix) is used, and UV ink (ink cured by irradiation of ultraviolet rays) is used from the inkjet head (DMC-11610) of the system in a normal temperature (25 ° C.) environment. I dipped it. The UV ink has a viscosity of 12 centipoise (millipascal second) and a surface tension of 28 millinewton meters.

  In the measurement data of the resonance frequency shown in FIG. 6, 10 droplets having a volume of 10 picoliter per droplet are continuously ejected at a substantially central position of the electrode 42 (see FIG. 1) of the crystal resonator 14. , A total of 100 picoliter droplets were measured.

  As shown in FIG. 6, the timing at which the resonance frequency becomes the minimum value is after a predetermined time has elapsed after the tenth droplet is deposited. The ten droplets that have landed at the same position from the timing at which the tenth droplet is ejected are combined into one droplet and spread, and the evaporation of the solvent proceeds to reach an equilibrium state.

When the liquid droplets that have landed on the crystal unit 14 are in an equilibrium state, the change in the resonance frequency of the crystal unit 14 converges to show a constant resonance frequency. The resonance frequency of the droplet reaching the equilibrium state is measured as “resonance frequency F ₂ after the droplet is deposited”.

  The time until the droplets are in an equilibrium state varies depending on the conditions of the liquid (the physical property values such as the volume and viscosity of the droplet to be measured) and the environmental conditions (temperature, humidity, etc.). In addition, when the equilibrium state is reached, the solvent component is completely volatilized and only solid matter remains, and the solvent component does not completely volatilize and reaches the equilibrium state while maintaining the liquid state. It is possible.

  That is, for the droplets that completely evaporate the solvent component and only the solid matter remains and reaches the equilibrium state, the mass of the solid matter in the droplets is measured, and the droplets that reach the equilibrium state while maintaining the liquid state are liquid droplets. The drop mass is measured.

  As droplets that can be measured by the mass measurement method shown in this example, various inks for inkjet recording apparatuses, resin liquids containing a photosensitive resin (resist liquid), and metal materials (Au, Ag, etc.) that form electrical wiring are used. The metal liquid to contain is mentioned.

  Examples of the liquid in which the solvent component is completely volatilized and only solids remain to reach an equilibrium state include liquids in which a volatile solvent such as water is used. Moreover, the liquid in which a high boiling point solvent (mixed solvent containing a high boiling point solvent) is used as a liquid which reaches an equilibrium state while maintaining a liquid state without completely evaporating the solvent component.

  Here, the limit volume of the droplet that can be attached to the quartz crystal resonator 14 is determined. For example, when measuring 100 droplets, the droplet ejection conditions (volume of one droplet, volume of droplet attached to one droplet position) so that the total amount of 100 droplets is less than or equal to this limit volume. ) Is decided.

The limit volume of the droplet is V _max (cubic meter), the surface area of the crystal unit 14 is A _Q (square meter), the resonance frequency F (hertz) when the droplet of the crystal unit 14 is not adhered, and the viscosity of the droplet is η (Pascal · second), and assuming that the density of the droplet is ρ _L (kilogram per cubic meter), V _max = A _Q × {η / (π × ρ _L × F)} ^1/2
It is represented by That is, the total volume V of the liquid droplets to be measured is given by the following equation: V ≦ A _Q × {η / (π × ρ _L × F)} ^1/2 (1)
Satisfy the condition of

Whether the judgment of the droplet has reached equilibrium, it is possible to change the resonant frequency F ₂ after being landed droplets is determined by whether within a predetermined range. Droplet if fluctuation of the resonant frequency F ₂ is within 1 Hz after being landed droplets can be determined to have reached the equilibrium state.

That is, as shown in FIG. 6, the droplet is attached while sampling and monitoring the resonance frequency (resonance frequency F ₁ before attachment of the droplet to be measured) at a predetermined time interval from the start of oscillation of the crystal unit 14. It is possible to determine whether or not the resonance frequency F ₂ has reached an equilibrium state while sampling and monitoring the resonance frequency F ₂ after the droplet to be measured is attached at a predetermined time interval. .

  Next, a method for measuring the mass of each of a plurality of droplets that are continuously ejected will be described.

  FIG. 7 schematically shows a plurality of droplets 80 and 80 in which droplets 80 and 80 ejected at different droplet ejection positions on the crystal resonator 14 (electrodes 42 and 44) are in an equilibrium state without being united. It is explanatory drawing shown in figure, and the state which made 10 droplets 80 and 80 land on 10 droplet ejection positions is illustrated. The volume of each droplet 80, 80 is 10 picoliters.

  In order to measure the mass of a plurality of droplets for each droplet (for each droplet ejection), the droplet ejection position is determined for each droplet ejection so that the droplets 80 and 80 are not united by the crystal unit 14. Is changed. Further, after the previously ejected droplet 80 reaches an equilibrium state (under the condition that the resonance frequency of the crystal resonator 14 corresponding to the previous droplet can be measured), the next droplet 80 is ejected.

  For example, by satisfying the condition that the landing position interval for each droplet exceeds the diameter of the droplet, it is possible to avoid the coalescence of the previously ejected droplet and the next ejected droplet. Further, when the landing time interval for each droplet satisfies a condition that exceeds the time required for each droplet to reach an equilibrium state alone, the resonance frequency of the crystal resonator 14 corresponding to the previous droplet can be measured. The droplet 80 can be ejected. The ten droplets 80 and 80 shown in FIG. 7 land at ten droplet ejection positions without being united with each other, and are isolated from each other and reach an equilibrium state.

  8 is a diagram showing the measurement results of the droplet shown in FIG. 7, and FIG. 9 is a partially enlarged view of FIG. The resonance frequency denoted by reference numeral 90 in FIG. 8 corresponds to the first droplet 80. The resonance frequencies denoted by reference numerals 92, 94, and 96 correspond to the second, fifth, and tenth drops.

  In the measurement results shown in FIG. 8, the droplet ejection time intervals of the first to the tenth droplets are 10 minutes (600 seconds). In any one of the first to tenth droplets 80, 80, the fluctuation of the resonance frequency converges until the next droplet is ejected, and the resonance frequency of the droplet can be measured. Yes.

  That is, in any case, the fluctuation of the resonance frequency converges within about 300 seconds (5 minutes) from the droplet attachment timing (timing when the frequency suddenly drops). Considering the measurement error, it can be said that the fluctuation of the resonance frequency converges within Hertz within 600 seconds (10 minutes) from the droplet attachment timing.

  9A is an enlarged view of the resonance frequency indicated by reference numeral 90, and FIGS. 9B to 9D are enlarged views of the resonance frequencies indicated by reference numerals 92, 94, and 96 of FIG. 8, respectively. Is. The resonance frequency fluctuations shown in FIGS. 9A to 9D are all within one hertz and satisfy the resonance frequency fluctuation condition of the resonance frequency measurement.

8 and 9, 1 drop at a resonant frequency _{F 2} is -2.5 Hz (central value), second drop of the resonant frequency _{F 2} is -7.5 Hz ([Delta] F = 5 Hz), 5 drop at the resonance frequency _{F 2} -22 Hz, the resonance frequency _{F 2} of the 10 drop at a -44.5 Hz.

Note that the sign of the measured value is given for the convenience of data processing, and when calculating ΔF, it may be handled as an absolute value in consideration of the magnitude relationship between F ₁ and F ₂ . The time required to reach the equilibrium state after depositing the droplets obtained in this way is stored as parameters such as the type of droplet, environmental conditions such as temperature and humidity, and the volume per droplet ejection position. This data can be used.

  A comparative example of this example will be described with reference to FIGS. FIG. 10 is an explanatory diagram schematically showing the droplets 80 ′ and 80 ′ united on the crystal unit 14, and FIG. 11 shows the measurement results of the droplets 80 ′ and 80 ′ shown in FIG. FIG. 12A to 12C are partially enlarged views of FIG.

  FIG. 12 (a) shows the resonance frequency of the first drop denoted by reference numeral 90 ′ in FIG. 11, and FIGS. 12 (b) and (c) represent the second drop denoted by reference numerals 92 ′ and 94 ′ in FIG. This is the resonance frequency of the fifth drop.

  The droplets illustrated in FIG. 10 are obtained by depositing six droplets 80 (illustrated by broken lines) at different droplet deposition positions, but the adjacent droplets 80 and 80 are united with each other to form three liquids. Drops 80 ′ and 80 ′ (illustrated by solid lines) reach an equilibrium state.

  If the droplets 80 and 80 landed on the crystal unit 14 are united, the resonance frequency of the first droplet shown in FIG. 12A is within one hertz. Although the measurement is possible, the fluctuations of the resonance frequency of the second and subsequent drops 80 and 80 do not converge within 1 Hz. Further, since the resonance frequency varies with each droplet (each droplet ejection), the resonance frequency is difficult to measure.

  In order to measure the mass of each of the plurality of droplets by using the mass measurement method using the QCM described above, the interval between the landing positions of the droplets 80 and 80 so that the droplets 80 and 80 do not coalesce. Satisfies the condition that the diameter exceeds the diameter of each of the droplets 80 and 80 and satisfies the condition for landing the next droplet 80 after reaching the equilibrium state after the droplet 80 has landed on the crystal unit 14. .

  As described above, the mass measurement method shown in this example reaches not only the mass of the solid matter of the droplet after the solvent component has completely evaporated, but also the liquid component without the solvent component being completely evaporated. The mass of the dropped droplet can also be measured.

  That is, it is possible to measure the mass (resonance frequency) of the liquid with the state where the wetting and spreading of the droplet converges (the state where the wetting and spreading does not proceed) as an equilibrium state.

Next, the condition of the contact angle of the droplet after landing will be described with reference to FIG. FIG. 13 shows a cross section of a droplet (dot). The volume of the droplet is V _A , the height is h, the radius is r, and the contact angle is θ. The contact angle θ is expressed by the following formula: θ = 2 × arctan (h / r)
It is represented by Therefore, the following formula V _A / r ³ = (π / 3) × [{(1-cos θ) × (2 + cos θ)} / {(1 + cos θ) × sin θ}]
Is derived. Further, the height h of the droplet is expressed by the following equation: h = r × tan (θ / 2)
Which is
h = [{3 × V _A × (1 + cos θ) × sin θ} / {π × (1-cos θ) × (2 + cos θ)}] ^1/3 × tan (θ / 2)
It can be expressed as. Here, the height h of the droplet is equal to or less than the “viscosity penetration degree” (right side of the following equation) which is a depth obtained by averaging the distance at which the vibration of the droplet interface enters the droplet.
h ≦ {η / (π × ρ _L × F)} ^1/2
It becomes. Therefore, the contact angle θ is
[{3 × V _A × (1 + cos θ) × sin θ} / {π × (1-cos θ) × (2 + cos θ)}] ^1/3 × tan (θ / 2) ≦ {η / (π × ρ _L × F) } ^1/2 (2)
Meet the conditions.

Based on the above formula (2), when the contact angle θ is calculated using the viscosity η of the liquid ejected from the inkjet head and the volume _{VA of} the droplet, the viscosity of 10 millipascal · second is obtained. When a droplet having a droplet is ejected, the contact angle θ of the droplet satisfying the condition of the above formula (1) is 1 degree or less, and such a state is considered to be an extended wetting (super lyophilic) state.

  FIG. 14 is an explanatory diagram of extended wetting and shows the relationship between the contact angle and the diameter with respect to the elapsed time after landing. The figure shows the change in contact angle with time (100) when silver (Ag) nano-ink is ejected onto a lyophilic substrate (one obtained by ultrasonically washing a quartz substrate using isopropyl alcohol). And a change in the diameter of the droplet (shown with reference numeral 102).

  As shown in the figure, it can be said that changes in both the contact angle and the diameter converge after 60 seconds from landing, so that even in the extended wetting (super lyophilic) state, wetting and spreading of the liquid droplets 60 after landing. It is expected to converge in about a second.

  FIG. 15 shows measurement data of resonance frequency in a droplet using a non-volatile solvent, and FIGS. 16A and 16B are partially enlarged views of FIG. FIG. 15 shows measured data of the resonance frequency when 10 droplets of 10 picoliters are deposited at the same droplet deposition position. 16A is an enlarged view of the resonance frequency denoted by reference numeral 110 in FIG. 15, and FIG. 16B is an enlarged view of the resonance frequency denoted by reference numeral 112 in FIG.

  It can be said that the droplet has landed at the timing of 600 seconds, and the fluctuation of the resonance frequency has converged after the timing of 700 seconds. That is, it can be said that the fluctuation of the resonance frequency converges within 1 Hz after 10 minutes (600 seconds) after the landing of the droplet.

  The mass measurement method described above can be used for verification of variation for each droplet ejection from the same nozzle. It can also be used to verify the variation in droplet ejection between nozzles.

  FIG. 17 shows the flow of measurement of the resonance frequency when a plurality of droplets are ejected from the same nozzle to different droplet ejection positions and used for verification of the ejection characteristics (variation of droplet ejection) of the nozzle alone. It is a flowchart to show.

  As shown in the figure, when resonance frequency measurement is started (step S10), oscillation of the crystal resonator 14 is started (step S12), and measurement of the resonance frequency (frequency measurement) is started (step S14). .

  The first droplet is ejected from the target nozzle to the first position of the crystal resonator 14 (step S16), and the resonance frequency of the crystal resonator 14 after the first droplet has landed is monitored (step S18). . In step S18, when the variation of the resonance frequency exceeds 1 Hertz (No determination), monitoring of the resonance frequency of the crystal resonator 14 is continued (step S18), and in step S18, the variation of the resonance frequency is 1. When the frequency is equal to or lower than hertz (Yes determination), the resonance frequency is stored in the storage unit 30 (see FIG. 1) (step S20 in FIG. 17).

  The resonance frequency stored in the storage unit 30 may be a maximum value of fluctuation or a minimum value. Moreover, it is good also as an average value and a center value.

  Thereafter, in step S22, it is determined whether or not there is a next measurement. If it is determined that there is a next measurement (Yes determination), the position of the inkjet head (see FIG. 1) corresponding to the next droplet ejection position. Is moved (step S24), the next droplet is ejected to the next ejection position (step S26), and the processing from step S18 to step S22 is repeated.

  On the other hand, if it is determined in step S22 that there is no next measurement (No determination), the resonance frequency measurement is terminated.

  The measurement value of the resonance frequency for each droplet ejection thus measured is stored in the storage unit 30 shown in FIG. The mass calculation unit 20 calculates the mass of the droplet or the solid mass of the droplet for each droplet by referring to the measured value of the resonance frequency for each droplet.

  FIG. 18 is a flowchart showing a flow of measuring the resonance frequency when a plurality of droplets are ejected from different nozzles to different droplet ejection positions and used for verification of ejection characteristics (variation in droplet ejection) between the nozzles. It is.

  In the flowchart shown in FIG. 18, step S24 of the flowchart shown in FIG. 17 is replaced with step S24 ', and step S23 is added between step S22 and step S24'.

  That is, when it is determined in step S22 that there is the next measurement (Yes determination), the nozzle that performs droplet ejection is changed (step S23), and the droplet ejection position is changed according to the changed nozzle (step S24). ').

  On the other hand, if it is determined in step S22 that there is no next measurement (No determination), the resonance frequency measurement is terminated.

  The measurement value of the resonance frequency for each nozzle measured in this way is associated with the nozzle (nozzle number) and stored in the storage unit 30 illustrated in FIG. The mass calculation unit 20 refers to the measurement value of the resonance frequency for each nozzle stored in the storage unit 30, and calculates the mass of the droplet or the solid mass of the droplet for each nozzle.

Note that the liquid droplets to be measured can be liquid droplets in which a plurality of liquid droplets are combined within a range not exceeding the maximum measurable volume V _max shown in the above formula (1). In other words, a plurality of droplets are ejected to the same droplet ejection position by a plurality of droplet ejections, and the mass of the droplet in which the plurality of droplets are united and integrated at the droplet ejection position is measured. Can do.

According to the mass measuring apparatus and the mass measuring method configured as described above, when a plurality of droplets are ejected at each of a plurality of droplet ejection positions on the crystal resonator 14, a plurality of droplets to be measured are measured. the total volume is below the limit volume V _max, with droplet ejection position interval in which a plurality of droplets between the measured no coalescence, the droplet ejection timing of the next droplet from droplet ejection timing of the droplets ejected previously The droplet is ejected so that the droplet ejection time interval exceeds the time from the arrival of the previously deposited droplet until it reaches the equilibrium state, so the resonance frequency corresponding to each droplet is highly accurate. The mass of the droplet to be measured is determined based on the measured resonance frequency.

  When the fluctuation of the resonance frequency after attaching the droplet to be measured becomes 1 Hertz or less, it is determined that the droplet to be measured is in an equilibrium state, so the fluctuation of the resonance frequency converges and becomes stable. The resonance frequency can be accurately grasped in the state.

  The mass measurement method shown in this example is applied to the measurement of minute masses of liquids such as water-based inks, solvent inks, and functional liquids (resist liquids, metal inks) used to form mask patterns and wiring patterns. Is possible.

  The mass measurement method (system) described above can also be grasped as a method invention including steps corresponding to each means constituting the apparatus.

[Appendix]
As will be understood from the description of the embodiments of the invention described in detail above, the present specification includes disclosure of various technical ideas including at least the invention described below.

(Invention 1): A droplet attaching step for attaching a droplet to be measured to an oscillated vibrator, and resonance of the vibrator before the droplet to be measured is attached to the oscillated vibrator. A frequency measurement step of measuring the frequency F ₁ and measuring the resonance frequency F ₂ of the vibrator after the droplet to be measured is attached, and before attaching the measured droplet to be measured on the basis of the difference between the resonant frequency F ₂ of the vibrator after deposition of the droplets of the measurement target and the resonant frequencies F ₁ of the oscillator, the mass of the droplets adhered to the vibrator or the A calculation step of calculating a mass of a solid substance contained in the droplet attached to the vibrator, wherein the droplet attachment step includes a surface area A _{Q of} a surface on which the droplet to be measured of the vibrator is attached, Resonance frequency F when the droplet is not attached, droplet to be measured Viscosity eta, is represented using the density of the measurement target droplet [rho, the total amount V of the droplet to be measured is attached to the vibrator, the formula _{V ≦ A Q × {η /} (π × ρ L × F)} satisfies ^1/2 of conditions, with depositing at least one drop of liquid droplets to be measured for each of a plurality of attachment positions of the vibrator, the object to be measured is attached to a different attachment positions droplets together Meet the condition of non-coincidence, and after the target droplet that has been deposited reaches equilibrium on the vibrator, the next droplet to be measured is deposited at the position where the next droplet is deposited. is, the frequency measuring step, for each of a plurality of attachment positions of the vibrator, the resonance frequencies F ₁ before the deposition of droplets of the measurement target on the vibrator was measured, it was attached to the vibrator After the measurement target droplet reaches an equilibrium state, the measurement target droplet is removed. Mass measurement method characterized by measuring the resonant frequency F ₂ of the vibrator after being deposited.

According to the present invention, the vibrator is adjusted so that the total amount of droplets to be measured attached to the vibrator represented by V ≦ A _Q × {η / (π × ρ _L × F)} ^1/2 is less than the total amount. The liquid droplets to be measured are attached, satisfying the condition that the liquids attached to different attachment positions do not coalesce, and after the previously attached liquid droplets have reached an equilibrium state, the next liquid droplet is applied to the next attachment position. The droplet to be measured is attached so that the condition for attachment is satisfied, and the resonance frequency of the vibrator after the droplet to be measured reaches the equilibrium state is measured as the resonance frequency of the vibrator after the droplet is attached. Therefore, the resonance frequency of the vibrator after the droplet is attached is accurately measured, and the mass of the droplet to be measured is accurately obtained.

  In the present invention, when the solvent component is completely evaporated in the equilibrium state, the mass of the solid substance in the droplet is measured, and when the solvent component is not completely evaporated in the equilibrium state, The mass is measured.

(Invention 2): Keep the mass measuring method according to the invention 1, the frequency measurement process, the variation of the resonant frequency F ₂ of the vibrator after deposition of the droplets of the measurement target becomes below 1 hertz In this state, it is preferable to measure the resonance frequency of the vibrator after the droplet to be measured is attached.

  According to this aspect, since the resonance frequency is measured in a state in which the fluctuation of the resonance frequency of the vibrator after the droplet to be measured has converged, the vibration after the droplet to be measured is adhered The resonance frequency of the child is measured more accurately.

  (Invention 3): In the mass measurement method described in Invention 1 or 2, it is preferable that the droplet attachment step has an attachment time interval of 10 minutes or more for droplets attached to different attachment positions.

  According to this aspect, after the previously attached droplet is surely in an equilibrium state, the next measurement target droplet can be attached to the next attachment position. It is possible to accurately measure the resonance frequency after the droplets are attached.

(Invention 4): In the mass measurement method according to any one of Inventions 1 to 3, when the liquid droplet to be measured is a liquid in an equilibrium state, the volume V _A of the liquid droplet to be measured, the measurement object Maximum height h in the equilibrium state of the liquid droplet, radius r in the equilibrium state of the liquid droplet to be measured, density ρ _L in the equilibrium state of the liquid droplet to be measured resonance when the droplet of the vibrator is not attached Using the frequency F, the contact angle θ of the liquid to be measured with respect to the vibrator is given by
[{3 × V _A × (1 + cos θ) × sin θ} / {π × (1-cos θ) × (2 + cos θ)}] ^1/3 × tan (θ / 2) ≦ {η / (π × ρ _L × F) } ^1/2
An embodiment that satisfies the following condition is preferable.

  According to this aspect, when the contact angle θ of the droplet with respect to the vibrator satisfies the above condition, the total mass of the liquid deposited on the vibrator contributes to the change in the resonance frequency of the vibrator.

(Invention 5): In the mass measurement method according to any one of Inventions 1 to 4, the oscillator is a crystal oscillator having a structure in which a crystal piece is sandwiched by an electrode pair, and the droplet to be measured is attached. The surface to be performed is one electrode of the electrode pair, and the calculation step multiplies the thickness of the crystal resonator by a constant determined by a cut surface when calculating the mass m of the droplet to be measured. The following expression ΔF = −2 × F ₀ ² × {m /, which is defined by the fundamental frequency F ₀ obtained by the above _equation , the elastic modulus μ of the crystal resonator, the density ρ of the crystal resonator, and the surface area A _E of the electrode. An embodiment using (A _E × (ρ × μ) ^1/2 )} is preferable.

  According to this aspect, the mass of the solid content in the droplet or the mass of the droplet can be calculated by calculation using the resonance frequencies before and after the droplet is attached to the vibrator.

In such an embodiment, when an AT-cut quartz piece is used, the elastic modulus μ of the quartz vibrator is 2.95 × 10 ¹⁵ dynes per square centimeter.

  (Invention 6): In the mass measurement method according to any one of Inventions 1 to 5, the droplet adhesion step is performed in such a manner that the droplets to be measured adhered to different adhesion positions are not bonded together. It is preferable that the attachment position of the droplet to be attached later is selected so that the interval between the attachment position of the deposited droplet and the attachment position of the droplet to be attached later exceeds the diameter of the droplet to be attached later.

  According to this aspect, the droplets attached to different attachment positions do not coalesce, and a preferable resonance frequency measurement is realized.

  (Invention 7): In the mass measurement method according to any one of Inventions 1 to 6, in the droplet adhesion step, droplets to be measured are ejected from an inkjet head having a plurality of nozzles, and the same A mode in which droplets to be measured are ejected from a nozzle to a plurality of different attachment positions is preferable.

  Based on the mass measured in such an aspect, it is possible to grasp the ejection characteristics of the same nozzle.

  (Invention 8): In the mass measurement method according to any one of Inventions 1 to 6, in the droplet adhesion step, droplets to be measured are ejected from an inkjet head having a plurality of nozzles, and a plurality of droplets are measured from different nozzles. A mode in which droplets to be measured are ejected at different attachment positions is preferable.

  Based on the mass measured in such an aspect, the ejection characteristics between the nozzles can be grasped.

(Invention 9): A vibrator for attaching a droplet to be measured, an oscillating means for oscillating the vibrator, and a resonance of the vibrator before the droplet to be measured is attached to the oscillated vibrator. Frequency measurement means for measuring the frequency F ₁ and measuring the resonance frequency F ₂ of the vibrator after the droplet to be measured is attached, and before the measured droplet to be measured is attached on the basis of the difference between the resonant frequency F ₂ of the vibrator after deposition of the droplets of the measurement target and the resonant frequencies F ₁ of the oscillator, the mass of the droplets adhered to the vibrator or the Calculating means for calculating a mass of solid matter contained in the droplets attached to the vibrator, and when the droplets to be measured are attached to the vibrator, the droplets to be measured by the vibrator are removed. surface area a _Q of the surface to be _adhered, when not to adhere the droplets Vibration frequency F, the viscosity of the measured droplets eta, is represented using the density of the measurement target droplet [rho, the total amount V of the droplet to be measured is attached to the vibrator, the formula V ≦ A _Q X {η / (π × ρ _L × F)} satisfying the condition of ^1/2 , and at least one droplet to be measured is adhered to each of the plurality of adhesion positions of the vibrator, and different adhesion positions After the liquid droplets of the measurement target attached to the liquid crystal satisfy the condition that the liquid droplets of the measurement target do not coalesce and reach the equilibrium state on the vibrator, the next liquid droplet attachment position The frequency measurement means applies the resonance frequency F ₁ before attaching the measurement target droplet to the vibrator for each of a plurality of attachment positions of the vibrator. The measurement target liquid droplets measured and adhered to the vibrator reach an equilibrium state. Later, the mass measuring device and measuring the resonant frequency F ₂ of the vibrator after deposition of the droplets of the measurement target.

  In this invention, the aspect provided with the means corresponding to each process described in invention 2 to 8 is preferable.

  (Invention 10): In the mass measurement apparatus according to Invention 9, it is preferable that the droplet to be measured is attached to the vibrator from an inkjet head having a plurality of nozzles.

  The mass measuring method and apparatus according to the present invention are effective in measuring the mass of a droplet to be ejected from a nozzle of an inkjet head or the solid content in the droplet.

  DESCRIPTION OF SYMBOLS 10 ... Mass measuring device, 12 ... Inkjet head, 14 ... Crystal oscillator, 15 ... Support part, 16 ... Oscillation circuit, 18 ... Resonance frequency measuring part, 20 ... Mass calculation part, 22 ... Droplet ejection control part. 24 ... moving unit, 26 ... head movement control unit, 28 ... system control unit, 30 ... storage unit, 80 ... droplet

Claims (10)

A droplet attachment step of attaching a droplet to be measured to the oscillated vibrator;
With measuring the resonant frequencies F ₁ of the oscillator prior to depositing the droplets of the measurement target on the oscillated so the vibrator, the resonance frequency F of the oscillator after deposition of the droplets of the measurement object A frequency measurement process for measuring ₂ ;
On the basis of the difference between the resonant frequency F ₂ of the vibrator after deposition of the droplets of the measurement target and the resonant frequencies F ₁ of the oscillator prior to depositing the droplets of the measurement object that is the measuring A calculation step of calculating a mass of a droplet attached to the vibrator or a mass of a solid substance contained in the droplet attached to the vibrator;
Including
In the droplet attachment step, the surface area A _Q of the surface on which the droplet to be measured of the vibrator is attached, the resonance frequency F when the droplet is not attached, the viscosity η of the droplet to be measured, the droplet to be measured The total amount V of droplets to be measured that adhere to the vibrator, expressed using the density ρ, is expressed by the following equation: V ≦ A _Q × {η / (π × ρ _L × F)} ^1/2
And at least one droplet of the measurement target is attached to each of the plurality of attachment positions of the vibrator, and the measurement target droplets attached to different attachment positions do not coalesce with each other. After the liquid droplet to be measured that has been filled and attached first reaches an equilibrium state on the vibrator, the liquid droplet to be measured next is attached to the position where the next liquid droplet is attached,
Said frequency measuring step, for each of a plurality of attachment positions of the vibrator, the resonance frequencies F ₁ before the deposition of droplets of the measurement target on the vibrator is measured, the measurement was attached to the vibrator mass measurement method characterized in that target droplets after reaching the equilibrium, measuring the resonant frequency F ₂ of the vibrator after deposition of the droplets of the measurement target. It said frequency measuring step, in a state in which the variation of the resonance frequency F ₂ of the vibrator after deposition of the droplets of the measurement object is equal to or less than 1 hertz, after depositing the droplets of the measurement object The mass measuring method according to claim 1, wherein a resonance frequency of the vibrator is measured.   3. The mass measuring method according to claim 1, wherein, in the droplet attaching step, an attachment time interval of droplets attached to different attachment positions is set to 10 minutes or more. When the liquid droplet to be measured is a liquid in an equilibrium state, the volume V _A of the liquid droplet to be measured, the maximum height h in the equilibrium state of the liquid droplet to be measured, and the equilibrium of the liquid droplet to be measured Using the radius r in the state, the density ρ _L in the equilibrium state of the droplet to be measured, and the resonance frequency F when the droplet of the vibrator is not attached, the contact angle θ of the liquid to be measured with respect to the vibrator is ,
[{3 × V _A × (1 + cos θ) × sin θ} / {π × (1-cos θ) × (2 + cos θ)}] ^1/3 × tan (θ / 2) ≦ {η / (π × ρ _L × F) } ^1/2
The mass measurement method according to any one of claims 1 to 3, wherein the following condition is satisfied. The vibrator is a crystal vibrator having a structure in which a crystal piece is sandwiched between electrode pairs, and the surface to which the liquid droplet to be measured is attached is one of the electrodes of the electrode pair,
In the calculation step, when calculating the mass m of the droplet to be measured, the fundamental frequency F ₀ obtained by multiplying the thickness of the crystal resonator by a constant determined by a cut surface, the elastic modulus of the crystal resonator μ, density ρ of the crystal resonator, surface area A _E of the electrode, and the following expression ΔF = −2 × F ₀ ² × {m / (A _E × (ρ × μ) ^1/2 )} It uses, The mass measuring method of any one of Claim 1 to 4 characterized by the above-mentioned.   In the droplet adhesion step, as a condition that the measurement target droplets adhered to different adhesion positions do not coalesce, an interval between the adhesion position of the droplets adhered earlier and the adhesion position of the droplets adhered later is set. The mass measurement method according to claim 1, wherein an attachment position of the droplet to be attached later is selected so as to exceed a diameter of the droplet to be attached later.   In the droplet adhesion step, the measurement target droplet is ejected from an inkjet head having a plurality of nozzles, and the measurement target droplet is ejected from the same nozzle to a plurality of different adhesion positions. The mass measuring method of any one of Claim 1 to 6.   The droplet deposition step includes ejecting a droplet to be measured from an inkjet head having a plurality of nozzles, and ejecting the droplet to be measured to a plurality of different deposition positions from different nozzles. Item 7. The mass measuring method according to any one of Items 1 to 6. A vibrator to which a droplet to be measured is attached;
Oscillating means for oscillating the vibrator;
With measuring the resonant frequencies F ₁ of the oscillator prior to depositing the droplets of the measurement target on the oscillated so the vibrator, the resonance frequency F of the oscillator after deposition of the droplets of the measurement object Frequency measuring means for measuring ₂ ;
On the basis of the difference between the resonant frequency F ₂ of the vibrator after deposition of the droplets of the measurement target and the resonant frequencies F ₁ of the oscillator prior to depositing the droplets of the measurement object that is the measuring Calculating means for calculating the mass of the droplet attached to the vibrator or the mass of the solid substance contained in the droplet attached to the vibrator;
With
When attaching the measurement target droplet to the vibrator, the surface area A _Q of the surface of the vibrator on which the measurement target droplet is attached, the resonance frequency F when the droplet is attached, the measurement target droplet The total amount V of the liquid droplets to be measured attached to the vibrator, expressed using the viscosity η of the liquid droplets and the density ρ of the liquid droplets to be measured, is given by the following formula: V ≦ A _Q × {η / (π × ρ _L × F)} ^1/2
And at least one droplet of the measurement target is attached to each of the plurality of attachment positions of the vibrator, and the measurement target droplets attached to different attachment positions do not coalesce with each other. After the liquid droplet to be measured that has been filled and attached first reaches an equilibrium state on the vibrator, the liquid droplet to be measured next is attached to the position where the next liquid droplet is attached,
Said frequency measurement means, for each of a plurality of attachment positions of the vibrator, the resonance frequencies F ₁ before the deposition of droplets of the measurement target on the vibrator is measured, the measurement was attached to the vibrator after the target droplet reaches equilibrium, the mass measuring device and measuring the resonant frequency F ₂ of the vibrator after deposition of the droplets of the measurement target.   The mass measuring apparatus according to claim 9, wherein a droplet to be measured is attached to the vibrator from an inkjet head having a plurality of nozzles.

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