JPH03156352A - Method and apparatus for measuring thermal diffusivity by ac heating - Google Patents

Abstract

PURPOSE:To make it possible to measure even material whose thermal diffusivity is small precisely and to make it possible to perform measurement including temperature dependency with a small-scale apparatus by making a current flow through a conductive thin film formed on a sample plate to be measured as an AC heat source. CONSTITUTION:A conductive thin film 2 is formed on at least one surface of a thin sample plate to be measured 1. A current is made to flow through the thin film 2, and an AC heat source which is heated with Joule's heat is provided. An AC which is modulated with a specified modulating frequency is made to flow through the AC heat source of the sample plate to be measured 1, and AC heating is performed. A response curve comprising a pressure wave corresponding to the AC heating is generated on the other surface facing the sample plate to be measured 1, and the phase of the response curve is measured. Thus the thermal diffusivity of the sample plate to be measured 1 in the direction of the thickness is computed. The sample plate to be measured 1 is made of high-molecular compound such as phenol, urea, melamine and the like. The thickness is sufficiently thin so that the thermal diffusion in the direction of the surface can be neglected. The conductive film 2 is made of, e.g. gold, silver, platinum and the like and formed by the method of sputtering or vapor deposition.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a 71-1 method for determining thermal diffusivity of a substance, an apparatus used therefor, and a method for measuring thermal conductivity, and in particular,
δ-1 constant method and device using an unsteady method (a method in which the temperature is varied without keeping it uniform) for accurately measuring the thermal diffusivity in the thickness direction of poorly conductive materials such as polymer compounds and ceramics, and its thermal The present invention relates to a thermal conductivity measuring method for determining thermal conductivity using a measured value of thermal diffusivity obtained by the diffusivity measuring method.

(Prior art) Thermal diffusivity and thermal conductivity are important physical property values for determining processing conditions and usage conditions when designing materials and product designs for various substances such as polymer compounds. be. In recent years, with the development of computers, a large number of various simulation programs have been developed, and material design and product design are frequently performed using these programs. For example, structural analysis to analyze the stress and deformation of processed products and structures, thermal conduction analysis to analyze heat transfer phenomena, etc. are already widely used in the world, and recently, they have been used to analyze the behavior of resin inside molds during injection molding. A number of methods such as thermal-hydraulic analysis have also been used. The analytical accuracy of these simulation programs is greatly influenced by the accuracy of the physical property values used in the analysis, as well as the content of the program. Therefore, highly accurate physical property measurements of target substances are desired in order to improve the analysis accuracy and to accurately perform material and product design.

In many cases, processed products are not only used at room temperature but also at high temperatures, and many polymeric materials are melted at high temperatures during processing and then heated to room temperature. The molding process involves cooling until it turns red. For this reason,
When designing materials and products that take into account the actual usage and processing conditions of the product, or when performing analysis based on actual phenomena, it is important to know the physical properties over a wide temperature range from room temperature to above the melting temperature. is necessary.

In recent years, processed materials have been frequently used in composite forms, and the combinations have become diverse and complex. When measuring the physical properties for material development and material design of such special processing materials, it is often difficult to obtain a large number of samples to be measured. In addition, it has become necessary to quickly obtain physical property values and reflect the results in development and design content without any time delay. requested.

Methods for measuring thermal diffusivity can be broadly divided into steady methods and unsteady methods. The characteristic of measuring thermal diffusivity using the unsteady method is that the thermal diffusivity is determined by forcibly creating a state of thermal non-equilibrium within the sample and measuring the temperature change in the sample that occurs as the state of thermal nonequilibrium is relaxed. This method has advantages such as significantly shorter measurement time than the steady method.

Typical conventional thermal diffusivity measurement methods using unsteady methods include the Angstrom method, flash method, and PAS.
There is a law. The Angstrom method is a rod-shaped sample whose cross-sectional area is sufficiently small compared to its length, and by bringing it into contact with a heat source that periodically heats and cools it, a periodic temperature change is generated at one end of the sample. As a result, a temperature wave is generated within the sample tJ, and the state in which this temperature wave propagates within the sample is measured at two or more measurement points at different distances from the heating point in the wave propagation direction. The temperature is observed by determining the IIFI, and the thermal diffusivity is calculated using the amplitude and phase of the temperature wave obtained at each measurement point.

In the flash method, a light-absorbing film is provided on one surface of a flat plate sample, and the film is irradiated with, for example, a laser pulse to instantaneously heat the film through light absorption, and the temperature rise in the absorption layer that occurs at this time is A method in which the temperature change that occurs on the surface of the sample on the opposite side of the irradiated surface is measured as a function of time after flash irradiation, and the thermal diffusivity is measured from the temperature vs. time curve obtained at this time. It is.

In the PAS method, a microphone for measuring sound pressure is installed in a sealed cell with a window that transmits light, and a light-absorbing film is installed on one side of the flat plate sample inside the cell, and a modulated light beam is passed through the window. When the temperature waves propagate, the opposite side of the sample causes periodic temperature changes, and the fluctuations in the pressure waves generated inside the cell are measured, and the phase and This is a method for determining thermal diffusivity using amplitude. (Part WB to be Solved by the Invention) The conventional n1 constant method described above has the following problems.

The Angstrom method requires a large amount of sample material as it is necessary to form the sample into a long rod shape, and requires extensive insulation equipment to minimize heat loss from the sample surface. Furthermore, it takes a relatively long time to measure, and the measurement target is limited to substances with a relatively high thermal diffusivity.

Since the flash method performs heating by light absorption, when measuring a transparent sample or a sample with low light absorption, it is necessary to coat the sample surface with an absorption layer for light absorption. Therefore, heat loss and uneven heating occur at the interface between the absorption layer and the sample, causing errors. Furthermore, since the measurement time is short, it is assumed that heat loss does not need to be taken into consideration; materials with high thermal diffusivity such as metals satisfy this assumption well, but thermal diffusivity such as polymer compounds satisfies this assumption. The smaller the ratio, the larger the error.

Since the PAS method also performs heating by light absorption, problems similar to those of the flash method occur, and since the PAS method uses a sound pressure detector to measure sound pressure, the influence of noise due to vibrations, noise, etc. is large.

Furthermore, with these measurement methods, it is difficult to measure the temperature dependence of thermal diffusivity, and even if it were to be measured, a large-scale device would be required.

The present invention solves the above-mentioned problems, enables highly accurate measurement even of substances with low thermal diffusivity, and requires only a small amount of sample to be measured.
The purpose of this invention is to provide a method and device for measuring thermal diffusivity, which can quickly measure thermal diffusivity including temperature dependence using a small-scale device.

(Means for Solving the Problems) The present invention provides a method for measuring thermal diffusivity in the thickness direction of a thin sample plate to be measured, which comprises forming a conductive thin film on at least one side of the thin sample plate to be measured. A current is passed through the thin film to create an AC heat source that generates heat due to the Joule heat, and an AC current modulated at a predetermined modulation frequency is passed through the AC heat source of the sample plate to generate AC heat, and the sample is heated. A response curve consisting of a pressure wave corresponding to the AC heat generation is generated on the other opposing side of the plate, and the phase of the response curve is measured to calculate the thermal diffusivity in the thickness direction of the sample plate to be measured. - Preferably, a conductive thin film is formed on one surface of a thin sample plate to be measured, and a modulated alternating current is passed through the conductive thin film to generate Joule heat from the sample. As an AC heat source that heats one side of the
The other surface opposite to the one surface is the surface to be measured, and the sample plate to be measured on which the alternating current heat source is formed is placed in a container equipped with a sound pressure detector in which a predetermined gas is sealed. The sound pressure detector is mounted so as to form a part of the wall surface, and the pressure wave generated in the container due to the temperature change of the subject Δp1 is measured by the sound pressure detector, and its output is amplified by the lock-in amplifier, and the sound pressure detector is connected to the AC heat source. The thermal diffusivity is determined from the correlation between the phase difference between the pressure wave and the alternating current component measured by the sound pressure detector and the square root of the modulation frequency of the alternating current flowing through the alternating current heat source.

The art material plate to be measured in the present invention is a poorly conductive substance that can be in the form of a film, sheet, or plate, and includes, for example, phenol, urea, melamine, polyester, evoquin, polyurethane, cellulose, polystyrene, polypropylene, Polyethylene, vinylidene chloride, polyamide, polyacetal, polycarbonate, polysulfone, ABS, polyphenylene oxide, polyethersulfone, polyarylate, acrylic, acrylonitrile, polyacrylonitrile, polyetheretherketone, polyetherketone, polyimide, polyolefin, etc. Molecular compounds■, cyanine, phthalocyanine, naphthalocyanine, nickel acetate, spiro compound, ferrocene, fulgide, imidazole, perylene, phenazine, phenothiazine,
Organic pigments such as polyene, azo compound, quinone, indigo, diphenylmethane, triphenylmethane, polymethine, acridine, acridinone, carbostyril, coumarin, diphenylamine, quinacridone, quinophthalone, phenosakidine, phthaloperinone, silica stone, diamond, garnet, corundum, Ruby, sapphire, agate, zeolite, diatomaceous earth, mica, halite, apatite, kaolin, chumolite, sillimanite, andalusite, barite, dolomite, moonstone, marble, serpentine, pavilion, bauxite, pennite, Quartz, olivine, gypsum, sulfur, barite, alum, fluorite, feldspar, talc, asbestos, limestone, dolomite, calcite, quartz, amber, spinel, alexandrite, emerald, topaz, cat's eye, jade, opal Glasses such as quartz glass, fluoride glass, soda glass, soda lime glass, barium-strontium glass, lead glass, aluminoborosilicate glass, borosilicate glass, aluminosilicate glass, silica glass, etc., AN 203 , MgAl 204 , B
eo.

S i C, A I N, MgO, PLZT, Y2
03.

ZrO, , TiO2, CaF2. GaAs.

PbO, Cab, La2O3, Si3N4 ra-S
It is made of fine ceramics such as t:H, etc., and its thickness is sufficiently thin to the extent that thermal diffusion in the plane direction can be ignored, so it is considered to be completely insulated in the plane direction.

Conductive materials used in AC heat sources generate heat due to Joule heat when current is passed through them.For example, gold, silver, platinum,
These include copper, iron, zinc, antimony, iridium, chromel, constantan, nichrome, aluminum, chromium, nickel, and carbon.

In addition, the conductive thin film used for the AC heat source is sufficiently thinner than the sample plate to be measured so that the interface with the sample plate to be measured can be ignored, and its heat capacity is i1? It is sufficiently smaller than the J constant sample plate, and is in complete contact with the limb Δp1 constant sample plate, so it is considered that one surface of the Yen1 constant sample plate itself is generating AC heat at the modulation frequency of the AC heat source.

The conductive thin film used in the AC heat source is produced by applying ions to the sample plate to be measured. 1. By irradiating the solid surface with ions, the atoms that make up the solid fly out, and by adsorbing them onto the surface, a thin film is created. sputtering, which involves evaporating a substance in a vacuum and adsorbing it onto a surface to form a thin film; coating, which involves applying a liquid or semi-liquid substance onto a surface; and adhesion, which consists of the same or different materials. Adhesive 70 is formed by pressing the surfaces together using a pressure bonding force without using a bonding agent made of the same or different materials on the surface, but methods using sputtering or steaming are Most preferred.

When forming a conductive thin film on a sample plate to be measured by sputtering, for example, when using gold, the sample plate to be measured is masked with a polyester film, etc., and then heated under vacuum at 1.2 kV.3. With a voltage and current of about 5mA,
Gold was adsorbed onto the 7I-1 constant sample plate for about 30 minutes to form a sample plate with a thickness of 10 to 5000 angstroms and a resistance value of 0.
It is preferable to form a conductive thin film of about 1Ω to 10Ω.

When forming a conductive thin film on a sample plate to be measured using a steam tube, for example, when using gold, mask the δ-1 constant sample plate with a polyester film, etc., and then heat the gold above its melting point under vacuum. The gold is evaporated by heating with electricity until the gold is absorbed onto the sample plate to be measured for about 30 minutes until the gold reaches a thickness of 10~
5000 angstroms, resistance value 0.1Ω to 10Ω
It is preferable to form a conductive thin film with a certain degree of conductivity.

When forming a conductive thin film on the sample plate to be measured by coating, apply a conductive paste such as silver paste to the sample plate to be measured, with a thickness of 10 to 5000 angstroms and a resistance value of 0.1Ω to
It is preferable to apply it evenly to about 10Ω.

When forming a conductive thin film on a δP1 constant sample plate by applying force, the thickness should be 10 to 5000 angstroms, and the resistance value should be 0.
．． For conductive thin films such as copper foil, gold foil, etc. of 1Ω to 10Ω,
It is preferable to apply the adhesive so thinly that the interface between the conductive thin film and the sample plate to be measured can be ignored, and completely adhere to the δ-1 constant sample plate so as not to peel off.

When forming a conductive thin film on the 11PI constant sample plate by pressure bonding, a conductive thin film such as copper foil or gold foil with a thickness of 10 to 5000 angstroms and a resistance value (approximately 1.1 Ω to IO kΩ) is bonded to the conductive thin film. It is preferable to press it against the sample plate to be measured and bring it into complete contact with a pressure force that is greater than the pressure force at which the influence of the interface with the δP1 constant sample plate can be ignored.

Hereinafter, the basic configuration and features of the present invention will be explained with reference to the drawings.

In Fig. 1, reference numeral 1 denotes a sample plate to be measured, which has a substantially constant thickness and is sufficiently thin to the extent that thermal diffusion in the plane direction can be ignored. When the part is square, the ratio (1/d) of the side length (N) to the thickness (d) is 10 or more, preferably 50 or more, more preferably 100 or more, and the upper limit of the thickness (d) is 2000.
μm or less, preferably 1500 μm or less, more preferably 1000 μm or less, and the lower limit of the thickness is within the range where the heat capacity of the conductive thin film formed on one side can be ignored, and the thickness is 0.
．． It is a film, sheet, or plate with a diameter of 0.01 μm or more, preferably 0.1 μm or more, and more preferably 1 μm or more. In addition, the sample plate 1 to be measured is made of a polymer compound,
A poorly conductive material such as ceramics whose resistivity is I
10'Ω・ω or more, preferably I x 10′Ω・ω
Above, more preferably I x 10'Ω・■ or more, and the upper limit of the resistivity may be as large as possible, but for example, 1×1021Ω・■ or less, preferably 1×
lQ 22Ω・(to) or less, more preferably lX
It is 1023Ω·c or less.

2 is a conductive thin film that serves as an AC heat source for AC heating one side of the sample plate to be measured using a modulated current, and its resistance value is 0.01Ω to 100Ω, preferably 0.05Ω to
50Ω, more preferably 0.1Ω to 10Ω. The conductive thin film that serves as the AC heat source is in complete contact with the sample plate to be measured, so that the interface between the sample plate and the AC heat source can be ignored, and its thickness is sufficiently thinner than that of the sample plate to be measured.
For example, 50,000 angstroms or less, preferably 1
0,000 angstroms or less, more preferably 50 angstroms or less
00 angstroms or less, and the lower limit of the thickness may be as long as an alternating current can be passed therethrough, but it is, for example, 1 angstrom or more, preferably 5 angstroms or more, and more preferably 10 angstroms or more.

As shown in FIG. 2, the sample plate to be measured is attached to the sealed container 3 in such a manner that the surface to be measured forms part of the wall surface of the sealed container to maintain airtightness, and the AC heat source 2 is connected to the AC current generator ( A modulated alternating current is applied by a function synthesizer (such as a function synthesizer) 4, and AC heating is performed by the Joule heat generated by the modulated alternating current. A microphone 5 as a sound pressure detector is installed in the sealed container 3 so as to maintain airtightness, and its output is amplified by a lock-in amplifier 6 to determine the alternating current component of the pressure wave inside the sealed container JP1.

The lock-in amplifier 6 is also called a synchronous rectifier circuit, and obtains a DC component by multiplying the reference AC wave from the AC power generator 4 and the detected wave. Since it has a predetermined iso-decorative bandwidth and has selectivity, noise at frequencies other than those of interest can be almost completely removed.

The output of the lock-in amplifier 6 is input to a data processing device (for example, a personal computer) 7, and the thermal diffusivity is determined. The method for calculating this thermal diffusivity is as follows.

Since the heat generated by Joule heat is maximum at its peak point regardless of whether the current is positive or negative, the period of temperature change is twice the period of the applied alternating current. Therefore, the alternating current component of the temperature change of the alternating current heat source 2 fluctuates at a frequency of f, where the frequency of the modulated alternating current is f/2. The fluctuating temperature is calculated by changing the angular frequency of the alternating current component of the temperature change to ω(-2πf
), T(t)−Tocos(ωt) ・+・+・+−1
1).

The sample plate 1 to be measured is made of a difficult-to-conduct material, but because its thickness is extremely thin, the thermal energy due to Joule heat from the AC heat source 2 is transferred only by heat conduction in the thickness direction, and is transferred to the opposite surface to be measured. This causes periodic temperature fluctuations in the gas in the sealed container that is in contact with the sample, and generates pressure waves that match the phase of the temperature fluctuations on the surface of the sample.

Assuming that the thickness of the constant sample plate 71P1 is d and the thermal diffusivity is α, the fluctuating temperature on the surface to be measured is T(t)=To exp(-n■欝d)cos(ωL-
A4q7d)・・・・・・・・・・・・(2) It becomes. When the phase difference between the temperature change between the AC heat source 2 and the surface to be measured is reached, △θ−T7d+β ・・・・・・・・・・・・
(3) becomes. Here, what is △θ? The phase delay due to thermal diffusion of the fjCDI constant sample plate, β, is an apparatus constant. This Δθ
coincides with the phase difference between the AC heat source 2 and the pressure wave generated in the gas in the sealed container that is in contact with the fixed surface 71FI.

Substituting ω-2πf into equation (3) and transforming it, we get △θ-d
T77Tv'TF-β ・・・・・・・・・・・・(
4) is obtained.

Therefore, for a sample plate to be measured whose thickness d is known, the modulation frequency is varied at at least two points to measure the phase difference Δθ between the pressure waves measured by the AC heat source and the sound pressure detector,
The rate of change (gradient, slope when graphed) of the phase difference with respect to the square root of the modulation frequency f is determined, and the thermal diffusivity α can be determined using equation (4).

The lower limit of the frequency range suitable for this measurement is the thermal diffusion length (μ,
-h77;) is the frequency at which the thickness of the sample plate to be measured is less than d, and the upper limit is the range in which the amplitude of the signal determined by the sound pressure detector is sufficiently larger than the noise. When the sample plate to be measured is a polymer film of about 100 μm, the optimum frequency range is between 0°01 and 100011z, preferably between 0.5 and 700 fiz, and more preferably between 0.1 and 50011z.

As shown in FIG. 3, all of these devices are controlled by a personal computer (CPU), and the measurement results are automatically processed, creating an integrated automated measurement system. By determining the measurement frequency range at the start of measurement, the output frequency of the function synthesizer, which is an alternating current generator, is automatically changed after measurement at each frequency is completed. Measured values by the lock-in amplifier are sent to a personal computer each time the n1 constant at each frequency is completed, and after the measurement is completed in a predetermined frequency range, those measured values are transferred to a floppy disk.
Saved to disk.

Expressing the relationship between thermal diffusivity and thermal conductivity, thermal conductivity is λ
, where the specific heat is Cp and the density is ρ, αsanλ/ (Cp・ρ
) ・・・・・・・・・(5), and when deformed, λ−αφCp・ρ ・・・・・・・・・(
6). Therefore, by using other measurement methods, ll? By obtaining the 1111 constant values of the specific heat and density, the thermal conductivity can be determined from equation (6) in conjunction with the measured value of the thermal diffusivity according to the present invention. Specific heat can be measured with a differential scanning calorimeter, adiabatic calorific value 51, etc., and density can be measured by volume expansion 11
, 1111 can be determined using a PVT measuring device, etc.
These measured values are used to determine thermal conductivity.

(Function) As described above, the present invention is capable of generating pressure waves in a sealed container induced by temperature changes between the heating surface and the other surface facing the heating surface when one side of the sample plate to be subjected to AC heating is applied. Utilizing the fact that the phase difference between By doing so, the Joule heat generates heat, one side of the sample plate to be measured is heated with alternating current, and the thermal diffusivity is determined by measuring the temperature change on the other side facing the heated surface using pressure waves. Since it has a simple structure of just forming a minute conductive thin film on a minute sample plate, it is easy to uniformly heat and cool the sample plate to be measured. It is possible to measure the temperature dependence of diffusivity, and the equipment may be simpler and smaller than other methods.

Further, the thermal conductivity can be determined from the thermal diffusivity obtained by the present invention and the measured values of specific heat and density determined by other methods.

(Example) Embodiments of the present invention will be described with reference to the drawings.

The sample plate to be measured has a thickness of 100 μm and a size of 10 m.
5X 10ms PET (polyethylene terephthalate) film, AC heat source to 300 angstrom thickness, polyester film 8-■X5
m■: This was masked and gold was sputtered.

FIG. 4 shows the change in the phase difference between the output from the AC heat source and the sound pressure detector due to the square root of the frequency due to the sample plate to be measured. From the slope obtained from this figure, the thermal diffusivity can be determined using the equation described above.

According to the 1mpJ standard method, since a lock-in amplifier is used, noise other than the required frequencies is almost completely removed, and the lI? Since I is constant, il depends on the absolute value of temperature? It is possible to obtain measurement data with constant error and constant aberration, high precision, and excellent reproducibility.

(Effects of the Invention) As explained above, according to the present invention, the following effects can be obtained, and the development of various materials such as polymer compounds and ceramics,
It can be suitably applied to fields such as product construction 1 and analysis using a simulator.

(1) According to the present invention, the phase difference of the AC component of temperature) F
Since the thermal diffusivity is determined by determining J, the absolute value of the temperature does not matter, and accurate measurements with few errors can be made. Further, since the sample plate to be measured has a WL amount and is thin, and has a simple structure in which a minute conductive thin film is directly formed on the sample plate to be measured, it is possible to miniaturize the apparatus and increase the speed of n1 constant. Therefore, various problems that the conventional angstrom method had, namely, a large amount of samples are required, a large amount of heat insulation equipment to minimize heat loss, a relatively long time is required for measurement, and the measurement target is All the problems of being limited to materials with a relatively high thermal diffusivity can be eliminated.

(2) The conductive thin film that serves as the AC heat source is formed in complete contact with the sample plate to be measured by sputtering, etc., and is so thin that the contact interface can be ignored, reducing heat loss between the sample plate and the heat source. It's not a problem. Therefore, it is possible to suppress the occurrence of heating unevenness and heat loss errors that occur in the flash method and PAS method that utilize light absorption. Furthermore, the present invention does not have the problem of noise caused by a chopper when switching light as in the PAS method.

(3) Since the sample is ultra-small and the equipment is also simplified and miniaturized, the measurement atmosphere of the part to be measured can be improved by heating and cooling the part to be measured in the container with the sample plate to be measured. The temperature can be changed to 8 and the temperature dependence of the thermal diffusivity can be measured.

When examining actual product usage conditions and processing conditions or performing analysis based on actual phenomena, it is necessary to know thermophysical properties over a wide temperature range from room temperature to above the melting temperature. Unlike conventional methods, the equipment does not become complicated or large due to bulk processing, and the thermal properties of the sample can be understood from multiple angles, making it flexible for research and development of material properties that are widely used in recent years. I can handle it.

(4) Thermal conductivity can be obtained from the measured values of the present invention and the measured values of specific heat and density determined by other methods.

When conducting research and development of +4 material properties in consideration of physical properties associated with heat transfer of materials, it is important to know not only thermal diffusivity but also thermal conductivity. It is possible to conduct research and development on multifaceted material properties based on both ratios.

[Brief explanation of the drawing]

Fig. 1 is a side view showing the structure of the sample plate to be measured in the present invention, Fig. 2 is a schematic diagram of the measuring device of the present invention, Fig. 3 is an example of an automated 71P + constant device Fig. 4 is a PET ( FIG. 3 is a diagram illustrating a typical example of a change in the frequency of the phase difference between an AC heat source and an AC component of the output of a sound pressure detector, determined by a polyethylene terephthalate film. In the figure, ]...Measurement sample plate 2...AC heat source (conductive thin film) 3...Sealed container 4...AC current generator (function synthesizer) 5...Sound pressure detector (microphone ) 6... Lock-in amplifier 7... Indicates a data processing device.

Claims (7)

[Claims] (1) A method for measuring the thermal diffusivity in the thickness direction of a thin sample plate to be measured, in which a conductive thin film is formed on at least one side of the thin sample plate to be measured and a current is passed through the thin film. An alternating current heat source that generates heat due to heat is used, and an alternating current modulated at a predetermined modulation frequency is passed through the alternating current heat source of the sample plate to be measured to generate alternating current heat, and the alternating current is applied to the other opposing side of the sample plate to be measured. Thermal diffusivity measurement of a thin sample plate in which the thermal diffusivity in the thickness direction of the sample plate is calculated by generating a response curve consisting of pressure waves corresponding to heat generation and measuring the phase of the response curve. Method. (2) A thin sample plate to be measured on which a conductive thin film to be used as an AC heat source is formed on one surface and the other surface opposite to the one surface to be measured, and a sound pressure detector inside. the sample plate to be measured is attached to the container so that the surface to be measured forms a part of the inner wall surface of the container, and the conductive thin film of the sample plate to be measured is covered with a predetermined amount. By passing an alternating current modulated at a modulation frequency of , the Joule heat generated by the alternating current is caused to generate alternating current heat, thereby causing a temperature change in the surface to be measured in response to the alternating current heat generation, thereby inducing a pressure wave within the container. , the phase of this pressure wave is measured by the sound pressure detector, and this is performed on the sample plate to be measured by changing the modulation frequency at least two points within the range of the modulation frequency, and the temperature change of the AC heat source is measured. a phase difference with the measured pressure wave generated in the container;
2. The method for measuring thermal diffusivity by alternating current heating according to claim 1, wherein the thermal diffusivity in the thickness direction of the measurement sample plate is measured based on the correlation with the modulation frequency. (3) The sample plate to be measured is a polymer compound, an organic pigment, an ore,
3. The method for measuring thermal diffusivity by alternating current heating according to claim 2, wherein the plate is made of a poorly conductive material selected from glass and ceramics. (4) The method for measuring thermal diffusivity by alternating current heating according to claim 2, wherein the conductive thin film serving as the alternating current heat source is made of a conductive substance that generates heat by Joule heat. (5) Formation of a conductive thin film that serves as an AC heat source by sputtering,
3. The method for measuring thermal diffusivity by alternating current heating according to claim 2, which is carried out by a method selected from vapor deposition, coating, adhesion, and compression bonding. (6) From the thermal diffusivity of the sample plate to be measured obtained by the method for measuring thermal diffusivity by alternating current heating according to claims 2 to 5, and the measured values of the specific heat and density of the sample plate to be measured, the thermal conductivity is determined. A method for measuring the thermal conductivity of the sample plate to be measured. (7) An apparatus for measuring the thermal diffusivity in the thickness direction of a sample plate to be measured, in which a conductive thin film is formed on one surface, and the other surface opposite to the one surface is the surface to be measured, , an alternating current supply means for supplying an alternating current modulated with a constant amplitude to the conductive thin film of the sample plate to be measured, and a sound pressure detector therein; A thermal diffusivity measurement device using AC heating, comprising: a container into which the sample to be measured can be mounted so as to form part of the inner wall; and a lock-in amplifier that amplifies the output from the sound pressure detector.