JPS6052189B2 - Reversible thermochromic coloring material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a colored material that changes color sensitively and reversibly in response to temperature changes.

In the present invention, discoloration refers to a concept that broadly includes changes in color, such as alcoholic color, color development, color density, and color change. Conventionally, regarding thermochromic materials using electron-donating color-forming organic compounds, Japanese Patent Publication No. 51-48085 and Japanese Patent Application Laid-Open No. 51-3108
Inventions such as the following are known.

The former has three essential components: (1) an electron-donating color-forming organic compound, (2) a compound having a phenolic hydroxyl group, and (3) a non-volatile compound that detracts from the color-forming reaction of the above two compounds. Examples of nonvolatile compounds that have the detracting effect include higher alcohols, polyethylene glycols, alkanolamines, various ethers, various esters, and quaternary ammonium salts. While the main purpose of conventional writing instruments was to leave records, this invention uses elements that can change the color of handwriting, such as alcoholic color and coloring, to Muro bamboo.
L thick A 藺Li あ I, ru. However, the coloring agent obtained by this invention has a wide discoloration temperature range and shows gradual discoloration, so it has the disadvantage that it is not sensitive to subtle temperature changes. The latter is (1) an electron-donating color-forming organic compound, (2) one or more compounds selected from compounds having a phenolic hydroxyl group, metal salts thereof, and metal salts of compounds having a carboxyl group, and (3) Heat containing as essential components an acid amide compound or the above Ξ type compound and (4) one or more compounds selected from alcohols, esters, ketones, ethers, thioethers, and aromatic hydrocarbon compounds. It is a color-changing material. This invention relates to an improvement of the above invention, and by using an acid amide compound, the discoloration temperature range is moved to the high temperature side, so that it can also be used for temperature distribution measurement of equipment that gets hot, such as electrical equipment and reactors. It is characterized by the following points. However, even this composition has the disadvantage that it has a wide discoloration temperature range and lacks the ability to sensitively detect subtle temperature changes. The present invention provides that, by using a fatty acid that is not disclosed in both of the above inventions as the Ξ component, a reversible thermochromic material having a narrow discoloration temperature range, that is, extremely sensitive to temperature changes, can be obtained. This was done based on this knowledge.

That is, the present invention provides (1) an electron-donating color-forming organic compound;
The present invention relates to a reversible thermochromic coloring material containing (2) an aromatic compound having a phenolic hydroxyl group and/or a carboxyl group directly bonded to a benzene ring, and (3) a fatty acid having 8 or more carbon atoms as essential components.

Electron-donating color-forming organic compounds (color formers) used in the present invention, i.e., organic compounds that develop or change color by reacting with the color developer described below, include triphenylmethane phthalides, fluorans, phenothiazines, Indole phthalides, leuco auramines, spiropyrans, rhodamine,
Any lactam or the like used as a coloring body for pressure-sensitive copying paper may be used. Several hundred types of these colored bodies have already been developed, and they come in a wide variety of colors, allowing for arbitrary color schemes. Typical color formers include triphenylmethane, pthalads, indoles, pthalads, leuco-auramines, spiropyrans, fluorans, phenothiazines, rhodamine lactams, etc.

In the above formula, the numbers in parentheses indicate the color at the time of coloration. In the present invention, an aromatic compound having a phenolic hydroxyl group and/or a carboxyl group directly bonded to a benzene ring is used as a color developer for coloring or changing the color of the color developer. In the present invention, the color developer refers to these compounds below. Conventionally, clay materials such as silton and clay have been used to color the above-mentioned coloring bodies, but it is not possible to obtain a practical reversible thermochromic material by using these materials. Preferred color developers with excellent color development properties include 4-tert-butylphenol, 4-oxydiphenyl ether, α-naphthol, β-naphthol, methyl p-oxybenzoate, p-oxyacetophenone, and 2,2″- Methylenebis(4-methyl-6-tertiaryisobutylphenol), p-phenylphenol, 4,4-isopropylidenediphenol (bisphenol A), 2,
2″-methylenebis(4-chlorophenol), hydroquinone, 2-oxy-1-naphthoic acid, 2-oxy-p-toluic acid, salicylic acid, m-oxybenzoic acid, 4
-Oxyphthalic acid, phloroglucincarboxylic acid, gallic acid, propyl gallate, phthalic acid, etc. are exemplified. These color developers can be used alone or in a mixture of two or more, and thereby the color change temperature can be adjusted. The mixing ratio of color developer to color former is usually about 1:1 by weight.
1 to 1:15. The fatty acids used in the present invention have the effect of enhancing color erasing and coloring effects, as well as erasing and coloring effects.
Gives color sensitivity. Preferable fatty acids in terms of availability are listed below, and the numbers in brackets are the melting points of pure fatty acids, and the discoloration temperature roughly approximates the melting point. Frilic acid (16.5℃), pelargonic acid (
13C), purinic acid (31.3℃), lauric acid (43.6C), myristic acid (58.00C), palmitic acid (62.9CC), stearic acid (69.9C)
°C), arachic acid (75.7C), behenic acid (80.7C),
C), lignoceric acid (84.2°C), and xerotic acid (87.7°C). The above fatty acids can be used alone. Alternatively, two or more types may be mixed and used. The amount of fatty acid blended is usually 1 to 10 parts per 1 part by weight of the color developer.
At 0% by weight and below 1% by weight, thermal discoloration becomes slow;
If the amount is 0% or more, the color itself becomes pale. The reversible thermosensitive (color-erasing) component consisting of the above three components can be used alone as a reversible thermochromic coloring material, but if desired, appropriate additives may be added to form a reversible thermochromic coloring material. . For example, by blending a non-decolorable dye or pigment, a thermochromic material whose color changes depending on the decolorization or color development of the thermosensitive decolorizable component can be obtained. The thermochromic coloring material may further contain other additives depending on its use. For example, when this coloring material is used in ink, paint, etc., thickeners, flow control agents, resins, solvents, etc. may be added. When using the material processed above, the necessary materials are used for each.These additives may be those that do not adversely affect coloring and decoloring.Reversible thermochromic coloring material according to the present invention Depending on the type of coloring material, the preparation method itself may be a conventional method adopted in each field.The coloring material according to the present invention can be used for printing ink, crayon, colored pencil, thermo paint,
Paints, felt-tip pens, carbon paper, etc.

Since the coloring material according to the present invention has a narrow discoloration temperature range, it can be used in fields that require high heat sensitivity, such as sensing inflamed areas and measuring body temperature in the medical field, accurate temperature distribution measurement in reaction vessels in the chemical field, and food products. It is particularly suitable for use in labeling of frozen foods in the field.

The present invention will be explained below with reference to Examples.

In the examples, parts are by weight unless otherwise specified.
Examples 1 to 11 Predetermined amounts of an electron-donating color-forming organic compound, a color developer, a fatty acid, and an additive were mixed, heated, and melted, and the decoloring temperature and color were observed.

The formulation and test results are shown in Table-1. Example 13 (
Example of decolorization point depression) When Example 1 and Example 3 are mixed in a ratio of 1:2, 33
It exhibits a dark blue color below 33.5°C, but turns colorless above 33.5°C.

Example 14 (stick paint) Approximately 50% calcium carbonate was added to the colorant raw material obtained in Example 5.
In addition, the mixture was kneaded, melted, and poured into a mold to obtain a rod-shaped (crayon type) writing instrument.

The image drawn with this writing instrument loses its color at 65°C and becomes dark blue below 65°C. Example 15 (color-changing coloring material) One portion of Oil Green 201 was added to the coloring material raw material obtained in Example 2.
Department and oil yellow? The colored material which is sufficiently dispersed by adding 0.5 part of the coloring material is brown at temperatures below 5rC, but exhibits a bright green color at temperatures above 57.5°C.

Example 16 (Ink for felt-tip pens) Five parts of the coloring material raw material obtained in Example 10 was dissolved in xylene 5-part and IPAW part to obtain a coloring material for felt-tip pens.

Images drawn with this colored material are vermilion at temperatures below 70°C, but completely disappear at 71°C. Reference Example 1 (Cold-set printed matter) The coloring material raw material of Example 12 was heated and melted, and an image was printed on high-quality paper using a heated gravure printing machine (MU type carbon printing machine manufactured by Ukita Kogyo Co., Ltd.). .

When he breathed on the image, it disappeared, and when he released his breath, the image reappeared. The raw materials in the above examples are as follows.

CVL: Crystal ● Violet ● Lactone PS: Vermilionni manufactured by Shin Nisso Kako Co., Ltd., a fluoran color-forming organic compound PS - Pinckini manufactured by Shin Nisso Kako Co., Ltd., a fluoran color forming organic compound Epolene E: Eastman●
Emulsified polyethylene oil green 201 manufactured by Chemical Co., Ltd.
: Anthoraquinone dye Oil Yellow 3G, manufactured by Chuo Gosei Co., Ltd.: Azo dye, manufactured by Chuo Gosei Co., Ltd. The coloring material of the present invention can be provided in various shapes and has various uses in a wide range of fields. is possible.

As printing ink, in addition to cold set ink, gravure ink containing a solvent or resin is also possible. It is also possible to encapsulate each of the coloring material raw materials of Examples 1 to 13 in microcapsules, and by mixing the respective microcapsules, it is possible to sense the temperature in stages. Comparative Example 1 This example uses the coloring material raw material of Example 12 of the present invention and the
This is a comparison between the technology of No. 1-48085 and Japanese Unexamined Patent Publication No. 51-3168.

The present invention uses stearic acid as the fatty acid, and
-48085 as the desensitizing nonvolatile compound and stearic acid amide as the acid amide compound in JP-A No. 51-31682 except that the same coloring agent and developer were used to observe the decoloring temperature range. .

The prescription is shown in Table-2. The above A, B and C were each blended, heated and melted, stirred and mixed uniformly and then applied onto high quality paper using a doctor blade in a coating amount of 3y/i. did.

These test papers were attached tightly to the outer wall of a thin aluminum container filled with water and equipped with a heater, a stirrer, and a thermometer. The aluminum container with the test paper attached is gradually heated (1°C/min) or naturally cooled, and the L value (whiteness) at a predetermined temperature is measured using a color difference meter (ND-K5 manufactured by Nippon Denshoku Industries Co., Ltd.). (The L value is a measure of whiteness, with black being 0 and white being 100.)

The L value of the white high-quality paper used is 84, and the basis weight is 64y/d.
It was hot. The results obtained are shown in FIG.

In the figure, A is the present invention, B is Japanese Patent Publication No. 51-48085, and C is
shows the change in L value when the temperature rises or falls of the thermochromic coloring material based on JP-A-51-3168 (
The horizontal axis represents temperature and the vertical axis represents L value). A↑ is related to A”
A↓ represents the change in the L value when the temperature rises (when discoloring), and A↓ represents the change when the temperature falls (when color develops) regarding A (the same applies to B and C). Note that the color change response to temperature changes is almost instantaneous, and the faster the temperature change, the faster the color change will occur. Furthermore, depending on the formulation, there may be a slight deviation in the color change temperature between decoloring and coloring, as shown in FIG. 1, but this deviation is much smaller than in conventional formulations. From FIG. 1, the maximum slope of the graph (Tan θ (↑) Max. and Tan θ (↓) Max) during decolorization and color development was determined.

The slope of this graph is the most important factor when identifying discoloration or color development with the naked eye, and the larger this value is, the narrower the discoloration temperature range is, indicating that the discoloration is more sensitive to temperature. The calculated values are shown in Table 3. As is clear from Table 3, the reversible thermosensitive color changing component according to the present invention is Tanθ (↑)
Both Max and TanO(↓)Max are large, and the decoloring sensitivity and coloring sensitivity to temperature changes are high. Therefore, the thermochromic coloring material blended with the same has excellent color change sensitivity.

Comparative Example 2 This is a comparison between Example 4 and the technology disclosed in Japanese Patent Publication No. 51-48085.

In the present invention, using trifurilic acid as a fatty acid,
The decoloring temperature range was observed using the same coloring agent and developer except that octyl alcohol was used as the desensitizing nonvolatile compound of No. 48085.

The prescription is shown in Table 4, and the color change due to temperature change is shown in Figure 2. Then, using the calculation method in Comparative Example 1, Tanθ(↑)
Max. ．． Table 5 shows the calculated values of tanθ(↓)Max.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a decolorization sensitivity curve showing the test results of Comparative Example 1.

Claims (1)

[Claims] 1. A reversible thermochromic coloring material containing as essential components an electron-donating color-forming organic compound, an aromatic compound having a phenolic hydroxyl group and/or a carboxyl group directly bonded to a benzene ring, and a fatty acid having 8 or more carbon atoms.