Low-temperature temperature indicator

Abstract

Temperature indicators using capsules containing a heat-melting substance can detect temperatures at much lower temperatures than conventional temperature indicators. However, the manufacturing of this type of temperature indicator is labor-intensive, difficult to mechanize, and therefore expensive. 【means】 A temperature-sensitive piece, on one side of a PET synthetic paper having an arbitrary planar shape, is printed with ink-like microcapsules containing a heat-melting substance that melts at a predetermined temperature and changes from solid to liquid. This piece is then placed on a sheet-like substrate surface with the microcapsule-printed side facing upwards. On top of this, a piece of colored paper having the same planar shape as the temperature-sensitive piece is placed with its colored side facing downwards. The entire surface of the substrate on which these temperature-sensitive piece and colored paper are superimposed is then covered with a transparent film to constitute a low-temperature indicator.

Description

Technical Field

[0001] The present invention relates to a thermosensitive device that utilizes the melting action of a chemical substance by heat, and more particularly to an irreversible type thermosensitive device for low temperatures that can sense temperature even in a low temperature region.

Background Art

[0002] Thermosensitive devices that irreversibly display the fact of exceeding the set temperature in terms of color by making the colored surface of a colored paper visible through the heat melting action of a heat-melting substance such as petroleum-based wax have high sensing accuracy at a relatively low cost, have little risk of malfunction, do not require auxiliary equipment such as a power source, and require only a small installation space. Therefore, they are widely used in many industrial fields that require heat management.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] General thermosensitive devices as shown in Patent Document 1 are usually assumed to be used in a temperature range of about 40°C to 280°C. However, in the food industry and other fields, there has also been a demand for thermosensitive devices that can sense temperature in a relatively low temperature range of 20°C or less, and in particular, in an extremely low temperature range of -40°C.

[0006] Conventional temperature indicators, such as those shown in Patent Document 1, utilize the melting action of thermally fused substances such as petroleum-based waxes. Therefore, if a thermally fused substance that melts even in a relatively low temperature range of 20°C or below is used, this thermally fused substance will naturally melt and liquefy in a higher temperature range. Consequently, with conventional temperature indicators, the thermally fused substance melts during storage or transport before it can be used for temperature detection, causing the colored surface of the colored paper to become transparent, making temperature sensing in low-temperature ranges impossible.

[0007] Therefore, as shown in Patent Document 2, an irreversible type of low-temperature color-sensitive thermometer has been proposed that can adequately detect temperature not only in relatively low temperature ranges of 20°C or below, but also in extremely low temperature ranges of -40°C.

[0008] The thermometer shown in Patent Document 2 comprises a container consisting of a bottom plate and a short peripheral wall rising upward from the periphery of the bottom plate. Inside this container are spherical capsules approximately 3 to 7 millimeters in diameter, each containing a thermally soluble substance that melts and changes from a solid to a liquid at an arbitrary set temperature. Above the container, a piece of colored paper, with one side being colored, is positioned with the colored side facing downwards via a spacer installed inside the container. Furthermore, a transparent resin plate is fitted onto the top surface of the colored paper so as to close the upper opening of the container.

[0009] In the irreversible type of low-temperature temperature indicator described in Patent Document 2, even if left at room temperature until put into service, the thermally fused substance is sealed in a capsule, so this thermally fused substance does not seep into the colored paper. Therefore, the colored surface of the colored paper does not become transparent before put into service, and it can be stored at room temperature until put into service. It can also perform irreversible temperature detection of an object in a relatively low temperature range of 20°C or below, which was impossible with conventional temperature indicators. Functionally, it is very superior, but it has drawbacks in terms of cost.

[0010] In other words, the capsule containing a thermally fused substance, which is the most important component of the irreversible type of low-temperature indicator described in Patent Document 2, has a diameter of about 3 to 7 millimeters. However, the manufacture of this capsule containing the thermally fused substance requires a lot of manual labor, making mechanization difficult and resulting in high production costs. Consequently, the indicator itself inevitably becomes expensive, greatly diminishing the value of color-changing type indicators, which have low cost as a major advantage.

[0011] As a result of diligent research, this invention successfully reduces the cost of an irreversible type low-temperature temperature indicator that can reliably detect temperature not only in relatively low temperature ranges of 20°C or below, but also at extremely low temperatures of -40°C, and is hereby proposed as the present invention. [Means for solving the problem]

[0012] The above problem was solved by constructing a low-temperature indicator by placing a temperature-sensitive piece, on one side of a PET synthetic paper having an arbitrary planar shape, printed with ink-like microcapsules containing a heat-melting substance that melts at a predetermined temperature and changes from solid to liquid, on a sheet-like substrate surface with the microcapsule-printed side facing upwards, and then placing a colored paper having the same planar shape as the temperature-sensitive piece on top of that with its colored side facing downwards, and finally covering the entire surface side of the substrate on which these temperature-sensitive piece and colored paper are superimposed with a transparent film. [Effects of the Invention]

[0013] If the low-temperature temperature-sensing device according to this invention is left at a temperature above the melting point of the thermally soluble substance enclosed in the microcapsule, the thermally soluble substance that provides temperature sensing will naturally melt. However, since the thermally soluble substance is enclosed in the microcapsule, it will not leak out to the outside at all, and the situation where the thermally soluble substance seeps into the colored paper and the colored surface becomes visible before use will not occur.

[0014] On the other hand, when preparing to use this low-temperature thermometer, immediately before use, the microcapsules printed on the temperature-sensing piece are destroyed by some means in the operating temperature atmosphere, for example, at a temperature of 20 degrees Celsius or lower. This exposes the thermally fused material contained within the microcapsules onto the temperature-sensing piece. Furthermore, the microcapsules can be destroyed by applying strong pressure to them, such as by passing the low-temperature indicator between a pair of rollers pressed together, as in a roller-type tube wringer or a roller-type manual laundry spin dryer, or by striking them with a hammer; the method is not limited.

[0015] In this state, since the low-temperature indicator is placed in a service temperature atmosphere, for example, in a temperature range of 20°C or below, even if the microcapsules rupture and the thermally molten material is exposed from within, this thermally molten material remains solid and does not soak into the colored paper, nor does it cause the colored surface of the colored paper to become visible through it.

[0016] In this state, the low-temperature indicator is attached to the object whose temperature needs to be detected and put into use. When the object reaches a preset temperature, the heat-melting substance melts and changes from solid to liquid, soaking into the colored paper. The previously opaque main body of the colored paper becomes semi-transparent, and the colored surface, which was previously invisible from above, becomes visible through the transparent film, thereby irreversibly indicating that the set temperature has been exceeded.

[0017] Thus, in the low-temperature temperature indicator according to this invention, even if left at room temperature until put into service, the heat-melting substance will not seep into the colored paper, the colored surface of the colored paper will not be visible through it, it can be stored at room temperature until put into service, no special temperature control is required during transport, and it fully utilizes the advantages of color-emitting temperature indicators such as ease of installation, no power supply required, high accuracy, and high durability, while irreversibly detecting the temperature of an object in the low-temperature range that is impossible to measure with general temperature indicators.

[0018] Moreover, the microcapsules encapsulating the heat-melting substance are made into ink, and the attachment of the microcapsules to the temperature-sensitive piece is performed by printing, so a series of manufacturing operations can be mechanized, which is suitable for mass production and can be produced at a much lower cost compared with the conventional ones.

Brief Description of the Drawings

[0019] [Figure 1] An enlarged cross-sectional view of Example 1 of the low-temperature temperature indicator according to this invention. [Figure 2] Similarly, an enlarged perspective view drawn with a part thereof cut away. [Figure 3] Similarly, an enlarged cross-sectional view drawn in an even more enlarged manner to explain the relationship between the temperature-sensitive piece, which is the most important component in this invention, and the colored paper. [Figure 4] Similarly, an enlarged cross-sectional view of the microcapsules showing the encapsulation state of the heat-melting substance. [Figure 5] Similarly, an enlarged perspective view drawn by separating these to explain the mutual positional relationship among the base material, the temperature-sensitive piece, and the colored paper. [Figure 6] Similarly, a side view showing an example of the method for destroying the microcapsules.

Modes for Carrying Out the Invention

[0020] In the low-temperature temperature indicator using microcapsules encapsulating a heat-melting substance that melts at a preset arbitrary set temperature and changes from a solid to a liquid inside, the greatest feature lies in the fact that the fixing of the microcapsules to the temperature-sensitive piece is performed by printing.

Examples

[0021] Referring to FIGS. 1 to 6, Example 1 of the low-temperature temperature indicator according to this invention will be described.

[0022] In the figure, 1 is a sheet-like substrate, and 2 is a temperature-sensitive piece made of PET synthetic paper having any planar shape such as a circle or a square. One side of this temperature-sensitive piece 2 has fine, ink-like microcapsules 3 printed on it, which contain a thermally soluble substance 8 that melts at a set temperature and changes from a solid to a liquid.

[0023] The thermally fused substance 8 is a chemical substance that melts at a predetermined temperature and undergoes a phase change from solid to liquid. Examples include petroleum waxes mainly composed of linear hydrocarbons, trilaurin, myristic acid, behenic acid, and stearic acid amide. The thermally fused substance 8 used in this invention is basically the same as the thermally fused substances used in conventional temperature-sensitive labels.

[0024] The microcapsules 3 containing the thermally fused substance 8 are very fine, with a particle size of approximately 100 to 300 μm, and use gelatin or melamine as the membrane material. The technical methods for forming microcapsules of this size and encapsulating chemical substances within them are already established in fields such as so-called "liquid crystal capsule printing," and are the same as those already used in many industrial fields.

[0025] In this embodiment, the particle size of the microcapsules 3 was set to 100 μm to 300 μm. However, if the diameter is smaller than 100 μm, it is difficult to break the microcapsules 3 immediately before use, and conversely, if the diameter is larger than 300 μm, it is difficult to form the ink. Therefore, the particle size of the microcapsules 3 is preferably 100 μm to 300 μm.

[0026] The PET synthetic paper that constitutes the temperature-sensitive piece 2 is a film-like material made from polyethylene terephthalate, which is water-resistant and printable, making it particularly suitable for printing and attaching the microcapsules 3. Therefore, it is used in this invention.

[0027] The temperature-sensitive piece 2, on which the microcapsules 3 are attached by printing, is placed on the substrate 1 with the printed side of the microcapsules 3 facing upwards. A colored piece of paper 4, having the same planar shape as the temperature-sensitive piece 2, is placed on top of the temperature-sensitive piece 2 with its colored side 5 facing downwards. The entire surface side of the substrate 1 on which these temperature-sensitive piece 2 and colored piece of paper 4 are superimposed is covered with a transparent film 6, forming the low-temperature temperature indicator 9 according to this invention.

[0028] This embodiment has the configuration described above. If it is left at a temperature above the melting point of the thermally fused substance 8 enclosed in the microcapsule 3, the thermally fused substance 8 that performs the temperature-sensitive function will naturally melt. However, since the thermally fused substance 8 is enclosed in the microcapsule 3, it will not leak out to the outside at all. This prevents the thermally fused substance 8 from seeping into the colored paper 4 before use, which would cause the colored surface 5 to become visible.

[0029] On the other hand, when preparing to use this low-temperature indicator device 9, immediately before use, in a service temperature atmosphere, for example at a temperature of 20°C or lower, the low-temperature indicator device 9 is passed between a pair of rollers 7.7 that are pressed against each other, as shown in Figure 6, to break the microcapsules 3 printed on the temperature-sensing piece 2 by the pressure of the pair of rollers 7.7, thereby exposing the heat-melting substance 8 enclosed in the microcapsules 3 onto the temperature-sensing piece 2. The structure of this pair of rollers 7.7 is the same as that of roller-type tube wringers and roller-type manual laundry wringers used in daily life. By passing the material between these rollers 7.7, the microcapsules 3 can be broken continuously and quickly. However, the method of destroying the microcapsules 3 is not limited to this pair of rollers 7.7; the microcapsules 3 can also be broken by striking them with a hammer or other means.

[0030] When the microcapsule 3 is destroyed, the low-temperature indicator 9 is placed in a service temperature atmosphere, for example, in a temperature range of 20°C or lower. Therefore, even if the microcapsule 3 breaks and the thermally molten material 8 is exposed, the thermally molten material 8 remains solid and does not seep into the colored paper 4, even if it comes into contact with it, and the colored surface 5 of the colored paper 4 does not become visible through it.

[0031] In this state, the irreversible type of low-temperature indicator 9 is attached to the object whose temperature needs to be detected and put into use. When the object reaches a preset temperature, the heat-melting substance 8 melts and changes from solid to liquid, seeping into the colored paper 4. The main body of the colored paper 4, which was previously opaque, becomes semi-transparent, and the colored surface 5, which was previously invisible from above, becomes visible through the transparent film 6. Thus, the fact that the set temperature has been exceeded can be irreversibly detected.

[0032] Thus, in the irreversible type of low-temperature indicator according to this invention, even if left at room temperature until put into service, the thermally molten substance 8 will not seep into the colored paper 4, and it can be stored as is until put into service. No special temperature control is required during transportation, and it fully utilizes the advantages of color-emitting temperature indicators, such as ease of installation, no power supply required, high accuracy, and high durability, while irreversibly detecting the temperature of an object in the low-temperature range that is impossible to measure with general temperature indicators.

[0033] Furthermore, the microcapsules 3 containing the heat-melting substance 8 are in ink form, and the attachment of the microcapsules 3 to the temperature-sensitive piece 2 is done by printing. This allows for the mechanization of the entire manufacturing process, making it suitable for mass production and enabling production at a much lower cost compared to conventional methods. [Industrial applicability]

[0034] While it can be used in any industrial sector requiring temperature detection, it is particularly valuable in fields such as the food industry, where products are frequently stored at low temperatures. [Explanation of Symbols]

[0035] 1 circuit board 2 temperature sensitive piece 3 Microcapsules 4. Colored paper 5. Colored surface 6 Transparent film 7 Rollers 8. Thermally fused materials 9. Low-temperature temperature indicator

Claims

1. A low-temperature indicator is characterized by the following: a temperature-sensitive piece, on one side of a PET synthetic paper having an arbitrary planar shape, is printed with ink-like microcapsules containing a heat-melting substance that melts at a predetermined temperature and changes from solid to liquid; this piece is placed on the surface of a sheet-like substrate with the microcapsule-printed side facing upwards; a colored paper having the same planar shape as the temperature-sensitive piece is then placed on top of the temperature-sensitive piece with its colored side facing downwards; and the entire surface side of the substrate on which these temperature-sensitive piece and colored paper are superimposed is covered with a transparent film.

2. The low-temperature thermometer according to claim 1, characterized in that the thermally fused substance is a petroleum-based wax.

3. The low-temperature thermometer according to claim 1, characterized in that the particle size of the microcapsules is 100 μm to 300 μm.

Images