JPH0812161B2 - Method and apparatus for measuring thermal diffusivity by AC heating - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the thermal diffusivity of a substance, an apparatus used therefor, and a method for measuring the thermal conductivity, and particularly to the thickness of a polymer compound or an organic dye-based hardly conductive substance. Using the measurement method and device by the unsteady method (method that changes the temperature without keeping the temperature constant) and the measurement value of the thermal diffusivity obtained by the thermal diffusivity measurement method that accurately measures the thermal diffusivity in the direction The present invention relates to a method for measuring thermal conductivity for obtaining thermal conductivity.

[0002]

2. Description of the Related Art Thermal diffusivity and thermal conductivity are one of the important physical property values in determining material design of various substances such as polymer compounds, processing conditions when designing products, and usage conditions. is there. In recent years, various simulation programs have been developed with the development of computerization, and material design and product design using them have been frequently performed. For example, structural analysis, which analyzes the stress and deformation of processed products and structures, and heat conduction analysis, which analyzes heat transfer phenomena, have already been widely used in the world.Recently, analysis of resin behavior in a mold during injection molding has been performed. Thermal fluid analysis, etc., have been widely used. The analysis accuracy of these simulation programs is greatly influenced not only by the contents of the programs but also by the accuracy of the physical property values used for the analysis. Therefore,
Highly accurate physical property measurement of a target substance is desired in order to improve the analysis accuracy and accurately perform material design and product design.

[0003] Actually processed products are used not only at room temperature but also at high temperatures in many cases, and many polymer materials and the like are melted at high temperatures during processing. After that, it goes through a molding process of cooling to room temperature. Therefore, when designing materials and products that take into consideration the actual use and processing conditions of the product, or when performing analysis based on actual phenomena, the physical properties in a wide temperature range from room temperature to the melting temperature or higher should be considered. It is necessary to know.

In recent years, processing materials have been frequently used in a composite form, and their combinations have become complicated in a wide variety of ways. In many cases, it is difficult to obtain a large amount of sample to be measured when developing such a special processing material and measuring the physical properties for designing the material. In addition, it has become necessary to quickly know physical property values and reflect the results in development and design contents without time delay.As a result, it is required to quickly measure physical properties with a small amount of sample. Has been done.

The measuring method of the thermal diffusivity is roughly classified into a steady method and an unsteady method. The characteristic of the thermal diffusivity measurement method by the unsteady method is that the thermal diffusivity is obtained by forcibly creating a thermal non-equilibrium state in the sample and measuring the temperature change of the sample accompanying the relaxation. Therefore, there is an advantage that the measurement time is significantly shorter than that of the stationary method.

Typical examples of conventional thermal diffusivity measurement methods by the unsteady method include the Angstrom method, the flash method, and the PAS method. In the Angstrom method, a portion of a rod-shaped sample whose cross-sectional area is sufficiently smaller than its length is brought into contact with a heat source that heats and cools the sample periodically, thereby causing a periodic temperature change at one end of the sample. As a result, a temperature wave is generated in the sample, and the state in which this temperature wave propagates in the sample changes the temperature at two or more measurement points at different distances from the heating point in the wave propagation direction. Is measured 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 is irradiated with, for example, a laser pulse to perform instantaneous heating by light absorption. The temperature change that propagates in the thickness direction of the sample and occurs on the surface of the sample opposite to the irradiation surface is measured as a function of the time after flash irradiation, and the thermal diffusivity is determined by the curve of temperature and time obtained at this time. It is a method of measuring.

In the PAS method, a microphone or the like for sound pressure measurement is installed in a closed cell having a window that transmits light, and a light absorption layer is provided on one side of a sample of a flat plate in the cell to modulate light. Irradiating the beam through the window gives a periodic temperature change, and the fluctuation of the pressure wave generated in the cell is measured by the periodic temperature change on the opposite side of the sample due to the propagation of the temperature wave. This is a method of calculating the thermal diffusivity using the phase and amplitude.

Further, as a method for rapidly and accurately measuring the thermal diffusivity with a small amount of sample, we have proposed an AC heating method (USP 5,080,495). Since this method has a simple structure in which a minute conductive thin film is formed on a minute sample plate to be measured, the measurement environment is uniformly heated,
It can be cooled easily, and the temperature dependence of the thermal diffusivity can be easily measured by arbitrarily changing the measurement atmosphere temperature.

[0010]

The conventional measuring method described above has the following problems. The angstrom method requires a large amount of sample material because it is necessary to mold the sample into a long rod shape, and a large amount of heat insulation system equipment is required to minimize heat loss from the sample surface. Moreover, the measurement requires a relatively long time, and the measurement target is limited to a substance having a relatively large thermal diffusivity.

Since the flash method performs heating by light absorption, it is necessary to apply an absorption layer for light absorption to the surface of the sample when measuring a transparent sample or a sample with little light absorption.
Therefore, heat loss and uneven heating occur at the interface between the absorption layer and the sample, which causes an error. In addition, it is assumed that the heat loss does not have to be taken into consideration because the measurement is performed for a short time, and this assumption is satisfied well for those with large thermal diffusivity such as metals, but the The smaller the spreading factor, the larger the error.

Since the PAS method also performs heating by light absorption,
The same problem as in the flash method occurs, and since the sound pressure is measured by a sound pressure detector, noise due to vibration, noise, and the like is large.

Furthermore, with these measuring methods, it is difficult to measure the temperature dependence of the thermal diffusivity, and a large-scale device is required even if it is measured. The AC heating method that we have proposed enables rapid measurement with a small amount of sample and facilitates temperature-dependent measurement. However, in the conventional AC heating method, in order to obtain the thermal diffusivity, it is necessary to change the modulation frequency of the AC heat source by at least two points and to measure the phase difference between the temperature wave on the heating surface and the back surface. However, the measurement takes some time, and problems may occur when measuring a substance having poor thermal stability at high temperature.

The present invention solves the above-mentioned problems, enables accurate measurement of a substance having a small thermal diffusivity, requires only a small amount of a sample to be measured, and can quickly perform measurement with a small-scale device including temperature dependence. The object of the present invention is to provide a method and an apparatus for measuring the thermal diffusivity, which enables accurate measurement even when measuring a substance having poor thermal stability at high temperature.

[0015]

According to the present invention, by improving the conventional method of thermal diffusivity by alternating current heating, the phase difference of the temperature wave between the heating surface and the back surface is measured for one modulation frequency. A method of quickly determining the thermal diffusivity is used to form or adhere conductive thin films on both sides of a thin sample to be measured.
One of the thin films is an alternating current heat source that applies a modulated alternating current to heat one side of the sample by its Joule heat.
The other is a resistance type thermometer that measures the temperature by using the voltage change caused by the temperature dependence of its resistance value by flowing a direct current, and locks the voltage change due to the temperature change of the resistance type thermometer. Measured by amplifying with an in-amplifier, the phase difference between the AC heat source and the AC component of the temperature change of the resistance thermometer, and the thermal diffusivity from the correlation between the square root of the modulation frequency of the AC current flowing in the AC heat source. It is characterized by measuring.

The present invention will be described in detail below. In the present invention
The sample to be measured is a film, sheet or plate, or
Is a hardly conductive substance that can be made into a liquid state. Phenol, urea, melamine, polyester, d
Poxy, polyurethane, cellulose, polystyrene, polyethylene
Lipropylene, polyethylene, vinylden chloride, polyurea
Mido, polyacetal, polycarbonate, polysulfo
Amine, ABS, polyphenylene oxide, polyether
Sulfone, polyarylate, acrylic, acrylic nitori
, Polyacrylonitrile, polyether ether keto
Resin, polyetherketone, polyimide, polyolefin
Polymer compounds such as. Cyanine, phthalocyanine, naphthalocyanine, d
Hackel vinegar, spiro compound, ferrocene, fulgide, i
Midazole, perylene, phenazine, phenothiazine,
Polyene, azo compound, quinone, indigo, diphenyl
Methane, triphenylmethane, polymethine, acrizi
, Acridinone, carbostyril, coumarin, diphe
Nilamine, quinacridone, quinophthalone, phenosaki
Organic dyes such as gin and phthaloperinone. Quartz stone, diamond, garnet, corundum, ruby
ー, sapphire, agate, zeolite, diatomaceous earth, mica, rock salt,
Apatite, kaolin, chumorchite, silica gemstone, beryl, indigo
Quartzite, dolomite, feldspar, marble, serpentine, peony,
Bauxite, bentonite, quartz, olivine, plaster,
Sulfur, barite, alum, fluorspar, feldspar, talc, stone
Cotton, limestone, dolomite, calcite, crystal, amber, spice
Flannel, alexandrite, emerald, topaz, cat
Ore such as eyestone, jade, and opal. Quartz glass, fluoride glass, soda glass, saw
Lime glass, barium strontium glass, lead gas
Glass, aluminoborosilicate glass, borosilicate glass,
Glasses such as aluminosilicate glass and silica glass. Al₂O₃, MgAl₂O_Four, BeO, SiC, A
IN, MgO, PLZT, Y₂O₃, ZrO₂, TiO
₂, CaF₂, GaAs, PbO, CaO, La
₂O₃, Si₃N_Four, A-SiH and other fine ceramics
The thickness is such that the thermal diffusion in the surface direction can be ignored.
Is thin enough that it is considered to be heat insulating in the plane direction.
You.

The conductive substance used for the AC heat source is a substance that generates heat by Joule heat when an electric current is passed through it.
Gold, silver, platinum, copper, iron, zinc, antimony, iridium, chromel, constantan, nichrome, aluminum, chrome, nickel, carbon and the like.

The conductive thin film used in the resistance type thermometer has a resistance value which changes with temperature. For example, gold, silver, platinum, copper, iron, zinc, antimony, iridium, chromel, constantan, nichrome, aluminum, Chrome, nickel, carbon, etc.

Further, the conductive thin film used for the AC heat source and the resistance type thermometer is sufficiently thin as compared with the sample to be measured so that the interface with the sample to be measured can be ignored.
Its heat capacity is sufficiently smaller than that of the sample to be measured, and it is in complete contact with the sample to be measured.Therefore, one surface of the sample to be measured itself generates AC heat at the modulation frequency of the AC heat source, and the temperature change of the other surface occurs. It is considered that the AC component is directly measured.

When the sample to be measured is solid, conductive thin films are formed on both sides of the sample to be measured. Sputtering that creates a thin film by adsorbing on the surface by utilizing the phenomenon that the atoms that make up the solid jump out when the surface of the solid is irradiated with ions. Vapor deposition in which a substance is evaporated in a vacuum and adsorbed on the surface to form a thin film. Application by applying a liquid or semi-liquid substance onto the surface. Adhesion that joins the surfaces with an adhesive consisting of the same or different substances. Crimping that joins with the crimping force by pressing without using an adhesive consisting of the same or different substances on the surface. The sample to be measured is melted and then solidified by cooling and solidification.
The method by vapor deposition is the most preferable.

When a conductive thin film is formed on a sample to be measured by sputtering, for example, when gold is used, the sample to be measured is masked with a polyester film or the like, and then 1.2 KV, 3.5 mA under vacuum. Gold was adsorbed on the sample to be measured at a voltage and current of about 30 minutes for a thickness of 10 to 5000 angstroms and a resistance value of 0.
It is preferable to form a conductive thin film of about 1 Ω to 10 KΩ.

When a conductive thin film is formed on a sample to be measured by vapor deposition, for example, when gold is used, the sample to be measured is masked with a polyester film or the like, and then gold is heated under vacuum to a temperature above its melting point. To evaporate, then 30
Gold is adsorbed on the sample to be measured for about 10 minutes to obtain a thickness of 10
Up to 5000 angstroms, resistance 0.1Ω to 10K
It is preferable to use a conductive thin film of about Ω.

When a conductive thin film is formed on the sample to be measured by coating, a conductive paste such as silver paste is applied to the sample to be measured so as to have a thickness of 10 to 5000 angstroms and a resistance value of 0.1 Ω to 10 KΩ. It is preferable to apply it uniformly.

When the conductive thin film is formed on the sample to be measured by adhesion, the conductive adhesive is applied to the conductive thin film such as copper foil or gold foil having a thickness of 10 to 5000 Å and a resistance value of about 0.1Ω to 10 KΩ. It is preferable that the thin film and the sample to be measured be thinly applied to the interface so that they can be ignored, and they should be completely adhered to the sample to be measured so as not to come off.

When a conductive thin film is formed on the sample to be measured by pressure bonding, a conductive thin film such as a copper foil or a gold foil having a thickness of 10 to 5000 angstrom and a resistance value of about 0.1Ω to 10 KΩ is used as the conductive thin film. It is preferable to press the sample to be measured and bring it into complete contact with a force equal to or higher than the crimping force at which the influence of the interface with the sample to be measured can be ignored.

When a conductive thin film is formed on a sample to be measured by fusion, a conductive thin film such as a sputtered film having a thickness of 10 to 5000 angstrom and a resistance value of about 0.1Ω to 10 KΩ, a vapor deposition film, a copper foil, a gold foil, etc. Is preferably melted and adhered to the sample to be measured, and then cooled and solidified, so that the sample is completely adhered to the extent that the influence of the interface between the conductive thin film and the sample to be measured can be ignored.

When the sample to be measured is liquid, the conductive thin film is Sputtering that creates a thin film by adsorbing on the surface by utilizing the phenomenon that the atoms that make up the solid jump out when the surface of the solid is irradiated with ions. Vapor deposition in which a substance is evaporated in a vacuum and adsorbed on the surface to form a thin film. Application by applying a liquid or semi-liquid substance onto the surface. It is formed on a glass plate or the like by bonding the surfaces together with an adhesive made of the same or different substance, but the method by sputtering or vapor deposition is most preferable.

When a conductive thin film is formed on a glass plate or the like by sputtering, for example, when gold is used, the glass plate or the like is masked with a polyester film or the like, and then 1.2 KV, 3.5 mA under vacuum. Gold is adsorbed on a glass plate or the like at a voltage and current of about 30 minutes for a thickness of 10 to 5000 angstroms and a resistance value of 0.
It is preferable to form a conductive thin film of about 1 Ω to 10 KΩ.

When a conductive thin film is formed on a glass plate or the like by vapor deposition, for example, when gold is used, after masking the glass plate or the like with a polyester film or the like, the gold is electrically heated to a temperature above its melting point under vacuum. To evaporate, then 30
Adsorb gold on a glass plate for about a minute, and
0-5000 angstrom, resistance value 0.1Ω-10
It is preferable to use a conductive thin film of about KΩ.

When a conductive thin film is formed on a glass plate or the like by coating, a conductive paste such as silver paste is applied to the glass plate or the like so as to have a thickness of 10 to 5000 angstroms and a resistance value of 0.1 Ω to 10 KΩ. It is preferable to apply it uniformly.

When a conductive thin film is formed on a glass plate or the like by adhesion, an adhesive is applied to a conductive thin film such as a copper foil or a gold foil having a thickness of 10 to 5000 angstrom and a resistance value of 0.1Ω to 10KΩ. It is preferable that they are completely adhered so that they do not come off from the glass plate or the like. When the sample to be measured is liquid, two conductive thin films formed on a glass plate or the like by any of the above methods sandwich the sample to be measured in liquid form, and the interface between the conductive thin film and the sample to be measured is Completely adhere to the extent that the influence can be ignored.

The basic structure and features of the present invention will be described below with reference to the drawings. FIG. 1 shows a case where the sample to be measured is a solid state, and 1 is a sample to be measured, which has a substantially constant thickness and has a shape thin enough to ignore thermal diffusion in the surface direction. When the thermal diffusivity measurement portion of the measurement sample is a square, the ratio of the length (l) of one side to the thickness (d) (l /
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 1
000 μm or less, and the lower limit of the thickness is 0.01 μm in a range where the heat capacity of the conductive thin film formed on both surfaces can be ignored.
Or more, preferably 0.1 μm or more, more preferably 1 μm or more.
It is a film or sheet or plate having a thickness of at least μm. The sample 1 to be measured is a highly conductive substance such as a polymer compound and ceramics, and its resistivity is 1 × 10 ⁴ Ω · cm.
As described above, the resistivity is preferably 1 × 10 ⁶ Ω · cm or more, more preferably 1 × 10 ⁷ Ω · cm or more, and the upper limit of the resistivity may be any value.
0 ²¹ Ω · cm or less, preferably 1 × 10 ²² Ω · cm or less, more preferably 10 ²³ Ω · cm or less.

Numeral 2 is the sample 1 to be measured by the modulated current.
Is a conductive thin film that serves as an AC heat source for AC heating one surface, and has a resistance value of 0.01 Ω to 100 KΩ, preferably 0.05 Ω to 50 KΩ, and more preferably 0.1 Ω to 1
0 KΩ. The conductive thin film 2 serving as an AC heat source is completely adhered to the sample to be measured 1 so that the interface with the sample to be measured 1 can be ignored, and the thickness thereof is sufficiently smaller than that of the sample to be measured 1, for example, 50,000 angstroms. The thickness is preferably 10,000 angstroms or less, more preferably 5000 angstroms or less, and the lower limit of the thickness may be any value as long as an alternating current can be applied. For example, 1 angstrom or more, preferably 5 angstroms or more, and more preferably 10 angstroms or more. is there.

Reference numeral 3 denotes a conductive thin film which serves as a resistance type thermometer for measuring the AC component of the temperature change on the surface of the sample 1 to be measured, which is opposite to the AC heat source, and has a resistance value of 0.01 Ω to 100K.
Ω, preferably 0.05 Ω to 50 KΩ, and more preferably 0.1 Ω to 10 KΩ. The conductive thin film 3 serving as a resistance thermometer is in complete contact with the sample to be measured 1 so that the interface with the sample to be measured 1 can be ignored, and the thickness thereof is sufficiently smaller than that of the sample to be measured 1, for example, It is 50,000 angstroms or less, preferably 10,000 angstroms or less, more preferably 5,000 angstroms or less, and the lower limit of the thickness is as long as it is possible to read a voltage change caused by passing a direct current and temperature dependence of resistance value. Although it is good, it is, for example, 1 angstrom or more, preferably 5 angstrom or more, and more preferably 10 angstrom or more.

FIG. 2 is a diagram showing a case where the sample to be measured is in a liquid state, (a) is a diagram showing a disassembled state, and (b) is a sectional view showing an assembled state. In the figure, reference numeral 1 is a sample to be measured, the thickness of which is kept substantially constant by a spacer 4 and is sufficiently thin so that thermal diffusion in the surface direction can be ignored. In the case of, the ratio (l / d) of the length (l) of one side 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,
The lower limit of the thickness is within a range in which the heat capacity of the conductive thin films adhered on both sides can be ignored, and is 0.01 μm or more, preferably 0.1 μm or more.
It is in the form of liquid having a size of at least μm, more preferably at least 1 μm. Further, the sample 1 to be measured is a hardly conductive substance such as a polymer compound and an organic dye, and its resistivity is 1 × 10 ⁴ Ω · cm.
As described above, the resistivity is preferably 1 × 10 ⁶ Ω · cm or more, more preferably 1 × 10 ⁷ Ω · cm or more, and the upper limit of the resistivity may be any value.
0 ²¹ Ω · cm or less, preferably 1 × 10 ²² Ω · cm or less, more preferably 10 ²³ Ω · cm or less.

Reference numeral 2 is a sample 1 to be measured by a modulated current.
Is a conductive thin film that serves as an AC heat source for AC heating one surface, and has a resistance value of 0.01 Ω to 100 KΩ, preferably 0.05 Ω to 50 KΩ, and more preferably 0.1 Ω to 1
0 KΩ. The conductive thin film 2 that serves as an AC heat source is formed on the lower surface of the upper glass plate 5 in FIG. 2, and is in complete contact with the sample to be measured so that the interface with the sample 1 to be measured can be ignored.
Its thickness is sufficiently smaller than that of the sample to be measured 1, for example, 50
000 angstroms or less, preferably 10,000 angstroms or less, more preferably 5000 angstroms or less, and the lower limit of the thickness may be any value as long as an alternating current can be applied, for example, 1 angstrom or more, preferably 5 angstroms or more, and more preferably 10 angstroms. That is all.

Reference numeral 3 is a conductive thin film which serves as a resistance type thermometer for measuring the AC component of the temperature change of the surface of the sample 1 to be measured, which is opposite to the AC heat source, and has a resistance value of 0.01 Ω to 100K.
Ω, preferably 0.05 Ω to 50 KΩ, and more preferably 0.1 Ω to 10 KΩ. The conductive thin film 3 serving as a resistance thermometer is formed on the upper surface of the lower glass plate 5 in FIG. 2 and is completely adhered to the sample to be measured 1 so that the interface with the sample to be measured 1 can be ignored. The thickness is sufficiently smaller than that of the sample to be measured 1, for example, 50,000 angstroms or less, preferably 10,000 angstroms or less, more preferably 5,000 angstroms or less, and the lower limit of the thickness is due to the temperature dependence of the resistance value when a direct current is applied. Any number may be used as long as it is possible to read the change in the voltage that occurs, for example, 1 angstrom or more, preferably 5 angstrom or more, and more preferably 10 angstrom or more.

An example of a method of adjusting the liquid sample unit to be measured will be described in more detail with reference to FIG. First, two glass plates 5 are prepared, and conductive thin films 2 or 3 having a size substantially equal to the size of the sample 1 to be measured are formed on the glass plates 5 by sputtering, vapor deposition, or the like. . Note that, as shown in FIG. 2, in order to energize the conductive thin films 2 and 3, a part of the thin film is extended to the outside of the spacer 4 and used as a lead wire.

Next, the spacer 4 is placed on the conductive thin film 3 on the lower glass plate 5. The spacer 4 has a function of holding the liquid sample 1 to be measured inside the spacer 4. The spacer 4 determines the thickness of the liquid sample 1 to be measured. If the spacer 4 is made of a hardly conductive substance,
Although not particularly limited, a polymer film having a thickness of about 0.1 to 2000 μm is usually preferable. The spacer 4 is appropriately selected according to the fluidity of the liquid sample 1 to be measured, such as a frame shape, a U-shape, and a two-shape. In FIG. 2, the frame type is shown.

In this way, the liquid sample 1 to be measured is injected into the space formed by the frame portion of the spacer 4 and the surface of the conductive thin film 3 which are installed. Another glass plate 5 on which the conductive thin film 2 is similarly formed is placed so that the conductive thin film 2 faces the sample to be measured 1 as shown in FIG. Thus, the liquid sample to be measured 1 is sealed in a thin film between the two glass plates 5 via the spacer 4 to form a sample to be measured unit. That is, in this unit, the liquid sample 1 and the two conductive thin films 2 and 3 are completely adhered and fixed. In terms of handling, it is more preferable that the entire unit is sealed with a suitable sealant, for example, an epoxy resin sealant, and sufficiently fixed.

As an example of the measuring device for the sample unit to be measured constructed as shown in FIG. 1 or 2, there is one shown in FIG. 3 or 4. In the measuring device of FIGS. 3 and 4, the AC heat source 2 is an AC current generator (function synthesizer, etc.).
An alternating current modulated by 6 is applied and is heated by the Joule heat. A direct-current power supply (battery or the like) 7 applies a constant direct-current voltage to the resistance thermometer 3, and a current that changes depending on the temperature dependence of the resistance value flows through the resistance 8. In the configuration of FIG. 3, the voltage drop at the resistor 8 is input to the lock-in amplifier 9 and amplified, and the AC component of the temperature change is measured. The lock-in amplifier 9 amplifies the voltage across the resistor 8 in the configuration of FIG. 3 as described above, but amplifies the voltage across the resistance thermometer 3 in the configuration of FIG. 4 to measure the AC component of the temperature change. ing.

The lock-in amplifier 9 described above is also called a synchronous rectification circuit, and obtains a DC component by multiplying the reference AC wave from the AC current generator 6 by the detected wave. This allows
Since it has a predetermined equivalent bandwidth and has selectivity, noise other than the required frequency is almost completely removed.

The output of the lock-in amplifier 9 is input to the data processing device (for example, personal computer) 10 and the thermal diffusivity is obtained. The calculation method of this thermal diffusivity is as follows.

Since the heat generated by the Joule heat is maximum at the peak point regardless of whether the current is positive or negative, the temperature change cycle is twice the cycle of the energized alternating current.
Therefore, when an AC voltage having an amplitude V _HO and a frequency ω / 2 is applied to the AC heat source 2, the surface of the sample to be measured has a frequency ω (= 2πf).
Is heated in. The Joule heat q generated per unit area of the sample surface to be measured is as a function of time t,

[0045]

[Equation 1]

Is represented by Here, _RH is the resistance of the AC heat source, and S is the area of the heating surface. The sample 1 to be measured is a poorly conductive material, but since its thickness is extremely thin, heat energy due to Joule heat of the AC heat source 2 is transferred only by heat conduction in the thickness direction, and a resistance thermometer on the opposite surface. 3 causes a periodic temperature change depending on the modulation frequency of the AC heat source 2.

The thickness of the sample 1 to be measured is d, the thermal diffusivity is α,
When λ is the thermal conductivity, the thermal diffusivity of the resistance thermometer 2 is α _S , and the thermal conductivity is λ _S , the fluctuation temperature is given by the following equation.

[0048]

[Equation 2]

However,

[0050]

(Equation 3)

Here, the thermal diffusion length μ _S = 1 / k is defined, and when the thickness of the sample is larger than the thermal diffusion length (d>
μ _S ), the temperature change of equation (2) is

[0052]

[Equation 4]

Focusing on the phase difference of the temperature change between the AC heat source 2 and the resistance type thermometer 3,

[0054]

(Equation 5)

It becomes Here, Δθ is a phase delay due to thermal diffusion of the sample 1 to be measured. Therefore, with respect to the sample to be measured 1 whose thickness d is known, the phase difference Δ of the AC component of the temperature wave between the AC heat source 2 and the resistance thermometer 3 at one modulation frequency.
By measuring θ, the thermal diffusivity α can be calculated using equation (4).
Can be requested.

The lower limit of the frequency suitable for this measurement is the frequency at which the thermal diffusion length μ _S becomes equal to or less than the thickness d of the sample to be measured,
The upper limit is the frequency at which the temperature amplitude measured by the resistance thermometer is sufficiently larger than the noise. The measured sample has a thickness of 100
In the case of a polymer film of μm, the optimum frequency is 0.
01Hz to 1000Hz, preferably 0.5Hz to 700Hz, more preferably 0.1Hz to 500H
between z.

The sample 1 to be measured is a heating / cooling cell 11
The temperature atmosphere of the measuring unit is controlled by the temperature controller 12. By changing the measurement atmosphere temperature, the temperature dependence of the thermal diffusivity can be measured at any temperature.

As shown in FIG. 5, each device in the measuring device is controlled by, for example, a personal computer (CPU) which also has the function of the above-described data processing device 10, and the measurement result is automatically processed. A batch automated measurement system has been implemented. The measured values by the lock-in amplifier are sent to the personal computer each time the measurement is completed, and the measured values are stored in the storage means such as a floppy disk. In addition, by determining the measurement temperature at the start of measurement, after the measurement at each temperature is completed, the temperature is raised or lowered to the next temperature and automatically measured until the measurement at the specified temperature is completed. Repeated.

The thermal diffusivity is expressed by a relational expression with the thermal conductivity. The thermal conductivity is λ, the specific heat is Cp, and the density is ρ.

[0060]

(Equation 6)

Then, when transformed,

[0062]

(Equation 7)

It becomes Therefore, by obtaining the measured values of the specific heat and the density measured by another measuring method, the thermal conductivity can be obtained from the equation (6) together with the measured value of the thermal diffusivity according to the present invention. The specific heat can be measured with a differential scanning calorimeter, an adiabatic calorimeter, etc., and the density is a volume expansion meter, P-
It can be measured with a VT measuring device or the like, and those measured values are used for obtaining the thermal conductivity.

[0064]

As described above, according to the present invention, the phase difference of the temperature change between the heating surface and the other surface facing the heating surface when the one surface of the sample to be measured is subjected to the AC heating is the modulation frequency of the temperature change of the heating surface. Depends on this, a small conductive thin film is formed or adhered to a small sample to be measured, and an alternating current is applied to the conductive thin film to generate heat due to its Joule heat to heat one side of the sample to be measured. , The thermal diffusivity is obtained by electrically measuring the temperature change of the other surface facing the heating surface. Since it has a simple structure in which a minute conductive thin film is formed on or adheres to a minute sample to be measured, it is easy to uniformly heat and cool the measurement environment, and thermal diffusion can be performed by arbitrarily changing the measurement atmosphere temperature. The temperature dependence of the rate can be measured.

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

[0066]

An embodiment of the present invention will be described with reference to the drawings.
The measured sample has a length of 148 μm and a size of 18 mm ×
An AC heating source of 500 angstroms, a resistance thermometer of 800 angstroms on a 18 mm glass plate, a polyester film mask of 10 mm x 3 mm, and gold sputtered on each, and a thickness of 1
20μm, 15mm x 10mm polystyrene film, AC heating source 500 angstrom, resistance thermometer 800 angstrom thick, polyester film 100mm x 3mm like glass plate
The masks were masked and gold was sputtered on each.

FIG. 6 shows the change in the phase difference between the outputs of the AC components of the glass plate and the AC component of the resistance thermometer, which is caused by the square root of the frequency. The point where Δθ is 45 ° (π / 4) is an extrapolated value, but a linear relationship that passes through the point of 45 ° (π / 4) is obtained according to the above-described equation (4). According to this measurement method, since the lock-in amplifier is used, noise other than the required frequency is almost completely removed, and since it is a measurement of the phase difference, there is no measurement error due to the absolute value of temperature, good accuracy, and excellent reproducibility. The measured data can be obtained.

FIG. 7 shows the results of measuring the temperature dependence of the thermal diffusivity of the polystyrene film. The glass transition temperature of this sample to be measured is about 105 ° C., but the thermal diffusivity can be measured over a wide temperature range above the glass transition temperature as shown in the figure. Also, the thermal diffusivity has an interesting result that it has a peak in the vicinity of the glass transition point, and there is a large difference in the thermal diffusivity between the liquid state and the solid state.

As described above, according to the present invention, changes in the thermal diffusivity due to the higher-order structure of a substance or molecular motion can be grasped in detail, and product design at high temperature, which was conventionally difficult to evaluate, can be accurately performed. It can be carried out. In using various simulation programs, the actual processing temperature,
More accurate analysis can be performed at the operating temperature.

FIG. 8 shows the measured results of the thermal diffusivity of the polystyrene film in the present invention and the temperature dependence of the thermal conductivity obtained from the measured values of the specific heat and density by another method.
As the specific heat, a differential scanning calorimeter was used, and as the density, a measurement value obtained by a piston type PVT measuring device was used. Similar to the thermal diffusivity, the calculated thermal conductivity has a peak in the vicinity of the glass transition point, and the overall behavior is similar to that of the thermal diffusivity. It greatly contributes to the rate. From this result, as in the case of thermal diffusivity, it is possible to accurately perform product design at high temperature, which was difficult to evaluate in the past, and to actually use various simulation programs. It is possible to perform more accurate analysis at the processing temperature and the operating temperature.

[0071]

As described above, according to the present invention, the following effects can be obtained, and the present invention can be suitably applied to the fields of development of various materials such as polymer compounds and ceramics, product design and analysis by simulation. Is possible. (1) According to the present invention, since the thermal diffusivity is obtained by measuring the phase difference of the AC component of temperature, the absolute value of temperature does not matter, and accurate measurement with few errors can be performed. Further, since the sample to be measured is minute and thin and has a simple structure in which a minute conductive thin film is directly formed on the sample to be measured, it is possible to downsize the device and speed up the measurement. Therefore, there are various problems that the conventional angstrom method has, namely, a large amount of sample is required, a large amount of heat insulation system equipment is required to minimize heat loss, and a relatively long time is required for measurement. It is possible to eliminate all the problems that the material has a relatively large thermal diffusivity. Further, since the phase difference of the AC component of the temperature is measured at one modulation frequency, particularly rapid measurement can be performed, and accurate measurement can be performed even when measuring a substance having poor thermal stability at high temperature. (2) Since the conductive thin film that serves as an AC heat source and a resistance type thermometer is formed by sputtering or the like so as to be in complete contact with the sample to be measured, and the contact interface is thin enough to be ignored, the sample to be measured and the heat source and thermometer The heat loss during is not a problem. Therefore, it is possible to suppress the occurrence of heating unevenness and heat loss error as in the flash method and the PAS method using light absorption. Also,
Since the measurement is not performed using a sound pressure detector unlike the PAS method, it is not necessary to consider an error due to vibration or noise. (3) Since the sample is ultra-compact and the device is simplified and downsized, the measurement ambient temperature of the measurement target is measured by heating and cooling the measurement target in the cell in which the measurement target is mounted. Can be easily changed, and the temperature dependence of the thermal diffusivity can be measured.

When studying the actual use conditions and processing conditions of a product or performing an analysis based on an actual phenomenon, it is necessary to know the thermophysical properties in a wide temperature range from room temperature to the melting temperature or higher. According to the present invention, unlike the conventional method, the temperature dependency of the thermal diffusivity can be measured without complicating the device due to the treatment of the bulk or sealing the cell and increasing the size, and the thermal characteristics of the sample can be measured. It can be grasped from various aspects and can flexibly deal with recent research and development of various material properties. (4) The thermal conductivity can be obtained from the measured value according to the present invention and the measured values of specific heat and density obtained by other methods.

It is important to know not only the thermal diffusivity but also the thermal conductivity when researching and developing the material properties in consideration of the physical properties associated with the heat transfer of the material. Multi-faceted study of material properties based on both thermal conductivity,
Can do development.

[Brief description of drawings]

FIG. 1 is an explanatory view of a solid state sample unit to be measured.

FIG. 2 is an explanatory view of a liquid sample unit to be measured.

FIG. 3 is an explanatory diagram showing an example of a measuring device.

FIG. 4 is an explanatory view showing another example of the measuring device.

FIG. 5 is an explanatory diagram showing an example of automation of the measuring device.

FIG. 6 is a diagram showing a measurement example of the relationship between the phase difference and the square root of the frequency in glass.

FIG. 7 is a diagram showing an example of measurement of temperature dependence of thermal diffusivity of polystyrene.

FIG. 8 is a diagram showing a measurement example of temperature dependence of thermal conductivity obtained from measured values of thermal diffusivity of polystyrene and measured values of specific heat and density obtained by another method.

[Explanation of symbols]

1 sample to be measured 2 AC heat source (conductive thin film) 3 resistance thermometer (conductive thin film) 4 spacer 5 glass plate 6 AC current generator (function synthesizer) 7 DC power supply (battery) 8 resistance 9 lock-in amplifier 10 Data processor 11 Heating / cooling cell 12 Temperature controller

Continuation of front page (56) Reference JP-A-3-156351 (JP, A) JP-A-56-140246 (JP, A)

Claims (13)

[Claims] 1. A method for measuring a thermal diffusivity in a thickness direction of a thin sample to be measured, wherein a conductive thin film is formed or adhered on both surfaces of the thin sample to be measured, and an electric current is passed through one of the thin films. By using a measurement system as an AC heat source that generates heat by its Joule heat, and the other of the thin films is a resistance type thermometer that utilizes the fact that its resistance value changes depending on the temperature, the AC heat source of the sample to be measured has a predetermined value. The temperature change corresponding to the AC heat is caused in the resistance thermometer by flowing an AC current that is modulated at the modulation frequency to generate an AC heat, and the phase of the temperature change is measured at one modulation frequency. , A phase difference between a temperature change of the AC heat source and a temperature change measured by the resistance thermometer, and a correlation between the modulation frequency and a modulation frequency, a thin diffusivity to obtain a thermal diffusivity in the thickness direction of the measured sample. Measuring method of thermal diffusivity of measurement sample. 2. The method for measuring thermal diffusivity by alternating current heating according to claim 1, wherein the sample to be measured is made of a hardly conductive substance which is fixed or selected from a liquid. 3. The method of measuring thermal diffusivity by alternating current heating according to claim 2, wherein the liquid sample to be measured is a hardly conductive substance selected from a polymer compound and an organic dye. 4. The method for measuring thermal diffusivity by AC heating according to claim 2, wherein the solid sample to be measured is a hardly conductive substance selected from polymer compounds, organic pigments, ores, glass and ceramics. 5. The method for measuring a thermal diffusivity by AC heating according to claim 1, wherein the conductive thin film serving as an AC heat source is made of a conductive substance that generates heat by Joule heat. 6. The method for measuring a thermal diffusivity by alternating current heating according to claim 1, wherein the conductive thin film to be the resistance type thermometer is made of a conductive substance whose resistance changes with temperature. 7. The heat by AC heating according to claim 1, wherein the conductive thin film to be an AC heat source and a resistance type thermometer is formed by a method selected from sputtering, vapor deposition, coating, adhesion and pressure bonding. How to measure diffusivity. 8. The heat by AC heating according to claim 1, wherein the temperature dependency of the thermal diffusivity is measured by heating or cooling the sample to be measured, thereby changing the measurement atmosphere temperature of the sample to be measured to a desired temperature. How to measure diffusivity. 9. From the thermal diffusivity of the sample to be measured obtained by the method for measuring thermal diffusivity by alternating current heating according to claim 1, and the measured values of the specific heat and density of the sample to be measured,
A method for measuring the thermal conductivity of a sample to be measured for obtaining the thermal conductivity. 10. The thermal diffusivity in the thickness direction of a thin sample to be measured, which is made of a solid or a liquid and has conductive thin films on both sides, is 1
An apparatus for carrying out the method according to claim 1, wherein the measuring is performed at a modulation frequency of a point, the alternating current generating means supplying an alternating current having a constant amplitude modulation to one conductive thin film, and the other. Power source means for applying a predetermined DC voltage to the conductive thin film, and a lock-in amplifier for amplifying the voltage that changes due to the temperature dependence of the resistance value of the other conductive thin film. Thermal diffusivity measuring device by AC heating. 11. The thermal diffusivity measuring apparatus by AC heating according to claim 10, further comprising means for adhering a conductive thin film to a liquid sample to be measured. 12. The thermal diffusivity measurement apparatus according to claim 10, further comprising a cell for accommodating a sample to be measured. 13. The temperature dependency of thermal diffusivity can be measured by further comprising means for heating or cooling the sample portion to be measured in the cell containing the sample to be measured, by changing the measurement atmosphere temperature to a desired temperature. The thermal diffusivity measuring device according to claim 10, wherein the thermal diffusivity is measured by alternating current heating.