JPH01122926A - Reversible temperature indicating material - Google Patents

Abstract

PURPOSE:To contrive to form a reversible temperature indicating material having high heat resistance, capable of adjusting color tone for the purpose of application of wide uses, without damaging thermal change in color of thallium chromate, by subjecting thallium chromate and a vanadic acid compound to solid solution. CONSTITUTION:This reversible temperature indication material is obtained by subjecting thallium chromate and a vanadic acid compound to solid solution and is a compound shown by the composition formula: (1-z)Tl2CrO4-ZM<1>M<2>VO4. In the formula, M<1> is sodium or potassium; M<2> is calcium, strontium or barium; z is 0<z<1.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a reversible temperature indicating material, which is a type of temperature control material that utilizes the property of substances whose color tone changes with temperature.

[Problems with conventional technology]

Conventionally, reversible temperature indicating materials have been developed with emphasis on their ability to indicate temperature by rapidly changing color in response to temperature changes. Therefore, the materials that have been proposed and commercialized as reversible temperature indicating materials include metal iodides that change color due to phase transition, liquid crystals that change color due to changes in molecular orientation, and organic compounds that change color due to electron transfer. It is also a material that exhibits a dramatic change in color at certain temperatures. In addition, these reversible temperature-indicating materials have begun to be applied in a wide range of fields, ranging from semi-finished products such as conventional temperature-indicating paints and labenope crayons to thermometers, toys, and clothing. Active product development is currently underway.

However, if we look at the usage status of these materials and product groups,
- It is limited to applications that are mainly for occasional use, almost disposable, and use under relatively mild conditions of up to about 100'C.

This is because the heat resistance limit temperature of conventional products is low and decomposes in the temperature range of around 200°C.

This low heat resistance limit temperature of conventional materials imposes restrictions not only on the usage environment but also on processing methods and applicable products. Regarding processing methods, for example, baking, which is widely used as a coating method, cannot be used for painting, and in particular, baking cannot be used at all except at low temperatures. Furthermore, it is impossible to vitrify it using glazes used in the ceramic industry. Regarding applicable products, the thermal theory does not apply to those whose temperature may rise above the heat-resistant limit temperature, but there are other products with extremely long useful life, such as durable consumer goods, that are subject to temperature-indicating materials. It has been difficult to apply because it has low heat resistance and durability, and there is a risk that its commercial value will be significantly lowered due to fading.

There are many products for which temperature-indicating materials are desired.

However, in order to overcome the limitations of the usage environment, processing methods, and applicable products of conventional materials, it is necessary to increase the heat resistance temperature.
A heat-resistant temperature of However, this is not possible by simply improving conventional materials.

The present inventors, in order to obtain a thermochromic pigment having heat resistance,
We have investigated the thermochromic properties of various substances and improved the thermochromic properties. As a result, among the metal oxides investigated, ThCrO4 was found to be particularly excellent in thermochromic properties. However, T 12
If CrO4 is used as it is, the color tone will be fixed, so it is desirable to be able to adjust the color tone in order to use it for a wide range of applications.

In view of the above points, the present invention aims to adjust the ThCrO40 color tone.

[Purpose of the invention]

The present invention proposes a material that has a heat resistance temperature of at least 600° C. in order to obtain a reversible temperature indicating material whose color tone can be adjusted in order to be applied to a wide range of applications.

〔Example〕

Hereinafter, one embodiment of the reversible temperature indicating material according to the present invention will be described in detail.

The present inventors discovered ThCrO4 as a thermostatic material made of a metal oxide with excellent heat resistance, and investigated its thermostatic properties and thermal stability in detail. As a result, it was confirmed that ThCrO4 changed color from reddish yellow at room temperature to bright yellowish red at 150° C., and could be put to practical use as a thermostatic paint having heat resistance. However, ThCrO4
If left as is, the color tone will be fixed, and it is desirable to be able to adjust the color tone in order to use it for a wide range of purposes. The present invention was made for the purpose of adjusting the color tone of Tl2CrO4 without impairing its thermochromic properties.

The means used in the present invention are as follows. That is, for ThCrO4, M'M2VO<(M':N
The color tone was adjusted by solid solution of a or K, M2: Ca + Sr or Ba). At this time, a solid phase reaction was used as the reaction method for both. The reaction temperature was 50
The temperature range is from 0°C to 650°C.

Here, ThCrO4 used as a raw material is T I N
It is obtained by reacting O3 and KzCrO4 in an aqueous solution, and M'M2VO4 is obtained by reacting Cab, S
rO, BaO with KVO3 or NaVO3 at 500℃
The solid phase reaction was carried out in a temperature range of 650°C to 650°C.

Here, ThCrO4 and M'M2VO4 can be synthesized using conventionally known methods. The material according to the present invention is (1-z)ThCrO4-zM'
It is a compound having a composition of M2VO4. Here, M
is sodium or potassium and M2 is calcium, strontium or barium. Further, the range of Z is O<z<1.

The characteristics of this temperature-indicating material will be explained below. The sample used was obtained by finely pulverizing the sample obtained by performing the above-mentioned solid phase reaction.

The particle size at this time is approximately 1 μm.

First, substances of each compound corresponding to z=0.25, 0.50, and 0.75 were identified by powder X-ray diffraction.

The obtained X-ray diffraction peak showed a shift in d value depending on the component ratio. From this, these compounds are
It is thought that it is in solid solution throughout the entire area.

Regarding the color tone of these solid solutions at room temperature, T 12 Cr
When comparing samples in which O+ and M1M2VO4 are dissolved in solid solution, the color tone of the solid solution becomes a --like yellowish color compared to the color tone of ThCr0<. M1M in solid solution with ThCrO4
Among 2VO4, when M2 is strontium, the yellowish tendency is stronger, followed by calcium,
This was followed by Valium. To demonstrate this tendency, T 1
2Cro<and 0.5ThCrO4-0,5NaM2V
The diffuse reflection spectrum of O4 at room temperature was measured, and the resulting chromaticity coordinate values are shown in FIG. Furthermore, in Ml, a tendency to become yellowish was observed in the order of sodium and potassium. Moreover, this tendency increases as the solid solution ratio, that is, the binary value in the composition formula increases. Also, similar to Figure 1,
The change in color at room temperature depending on the solid solution ratio of (1-z)ThCr04-zNasrVo4 is shown in FIG. 2 using chromaticity coordinates.

As can be seen from this figure, the color tone at room temperature can be adjusted in the range from slightly reddish-yellow ThCrO4 to yellowish-greenish yellow by changing the solid solution ratio.

Next, the thermochromic properties will be described. In each solid solution,
Even if the solid solution ratio of M'M 2VO4 is increased, T
The thermochromic properties of 12Cr 04 do not deteriorate much. When each sample was heated to 150° C. and visually confirmed, sufficient thermal discoloration characteristics were confirmed even when the solid solution ratio Z was increased to about 0.9. Shigashi, MIM 2VO<
Since the color itself is white, extremely increasing the solid solution ratio 2 has the effect of diluting the color, which is not very preferable in practice. The range of Z that is considered to cause no practical problems is approximately 0.75 or less. The colors of several representative samples at room temperature, 75°C, and 150°C are expressed by three attribute values and are shown in Table 1. In addition, in order to show the difference between the room temperature color and the color at 75° C. and 150° C., the results of calculating the UV color difference are also shown in Table 1.

In the table, it can be seen that in the example in which NaCaVO< is dissolved in solid solution, the color difference is not significantly deteriorated even though the solid solution ratio is quite large at 0.5.

Table 1 Color and magnitude of discoloration at various temperatures For the solid solutions shown in the present invention, neither melting nor mass change due to decomposition was observed in the temperature range from room temperature to 600°C. In other words, these solid solutions can be heated from room temperature to 6
It can be said that it is thermally stable in a temperature range up to 00°C. In order to actually confirm this thermal stability, a test was conducted in which glaze was baked onto heat-resistant glass. This test is a test to confirm the suitability of the temperature-indicating material to a wide range of uses including processing methods. The glaze used contained lead oxide and boron oxide and had a relatively low melting point, with an internal melting point of 580°C. For 1 part of each solid solution sample having a solid solution ratio of 0.5, 1 part of the glaze was placed in a mortar, mixed well to form ink, and then screen printed on crystallized glass.

After drying the coated surface, baking was performed at 580° C. for 10 minutes. As a result of baking, no particular deterioration in color tone was observed, and the discoloration of the coated sample was similar to that in the powder state. It should be noted that with temperature-indicating paints such as metal iodides that have been commercialized in the past, it has not been possible to perform baking at high temperatures using glazes.

〔Effect of the invention〕

The advantages of the reversible temperature indicating material of the present invention are shown below.

(1) The color tone of T1zCrO4, which has much higher heat resistance than conventionally proposed reversible temperature indicating materials, can be adjusted without substantially impairing its thermochromic properties and heat resistance. This makes it possible to add reversible temperature indicating materials to areas that reach high temperatures, and by adjusting the color tone,
The scope of application can be further expanded.

Since coating methods using glazes and thermosetting resins, which were previously unavailable, can be used, there are fewer restrictions in terms of processing methods.

As it is a thermally stable metal oxide, it does not easily fade due to heat and has stable properties over a long period of time, making it possible to apply it to durable consumer goods. , the range of applicability can be widened because it can also respond to requests for color tone adjustment in design.

(2) As for the thermochromic properties of the material itself, there is no hysteresis in discoloration when the temperature rises or falls, and the reproducibility of temperature display is good.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 show graphs of color states of the reversible temperature indicating material according to the present invention.

Claims (1)

[Claims] 1. Obtained by solid solution of thallium chromate and vanadate compound, having the composition formula (1-z) Tl_2CrO_
4-zM^1M^2VO_4, M^1 is sodium or potassium, M^2 is calcium, strontium or barium, and z is in the range of 0<z<1. Material.