JPH0517867B2 - - Google Patents

Description

[Detailed description of the invention]

OBJECTS OF THE INVENTION This invention relates to thermochromic compositions. In particular, the present invention relates to a reversible thermochromic composition that changes color from orange to blackish brown when heated to any specific temperature in the range of 50 to 100°C, and quickly changes to orange again when cooled. As a reversible thermochromic composition for this purpose, a composition consisting of a leuco dye, a phenolic resin, and a desensitizer is widely used, but it has a problem of low light resistance and the toxicity of the phenolic resin. Compositions containing complex salts of mercury tetraiodide have been used as having high light resistance, but they have problems with the toxicity of heavy metals, and have the disadvantage that the discoloration is not sharp and it is difficult to measure the temperature accurately. Structure of the Invention The present invention overcomes the drawbacks of the prior art described above, and is characterized in that a ferric salt of an aliphatic monocarboxylic acid, and monooxybenzoic acid and/or monooxybenzoic acid ester are dissolved or dispersed in a vehicle. The present invention relates to a thermochromic composition. The ferric salt of aliphatic monocarboxylic acid (hereinafter referred to as coloring agent) used in this invention has a carbon number of 8 to
22 ferric carboxylates, i.e. ferric caprylate,
Ferric caprylate, ferric laurate, ferric myristate, ferric palmitate, ferric stearate, ferric arachinate, ferric behenate,
Examples include ferric erucate, and preferably ferric myristate, ferric palmitate, ferric stearate, and ferric behenate. The monooxybenzoic acid and monooxybenzoic acid ester (hereinafter referred to as color developer) used in this invention are ortho,
Any compound having a carboxylic acid group or carboxylic acid ester group bonded to any of the meta and para positions can be used. Examples of the group bonded to the carboxylic acid group constituting the monooxybenzoate ester include an alkyl group having 1 to 22 carbon atoms, a phenyl group, a benzyl group, and a cyclohexyl group. In this invention, the developer also includes monooxybenzoic acid derivatives and monooxybenzoic acid ester derivatives in which the benzene ring is substituted with an amino group, a nitro group, an alkyl group, or a halogen group. Specifically, salicylic acid, 3-oxybenzoic acid,
4-oxybenzoic acid, 2-oxy-4-aminobenzoic acid, 5-ethyl-3-oxybenzoic acid, 4-
Monooxybenzoic acid and its derivatives of nitro-3-oxybenzoic acid; ethyl salicylate, methyl 3-oxybenzoate, N-propyl 4-oxybenzoate, 5-amino-2-oxybenzoic acid, 5-
Phenyl methyl-3-oxybenzoate, 4-nitro-3-oxybenzoic acid, N-dodecyl 3-methyl-4-oxybenzoate, 3,5-dibromo-4
Examples include monooxybenzoic acid esters such as methyl -oxybenzoate and N-nonyl 2,3,5,6-tetrachloro-4-oxybenzoate, and derivatives thereof. Among these, N-propyl 4-oxybenzoate, benzyl 4-oxybenzoate, phenyl salicylate, and methyl 3-oxybenzoate are preferred because they have almost the same melting point as the ferric salt of aliphatic monocarboxylic acid, and cause sharp discoloration. Can be used. Vehicles used in this invention can be those commonly used in printing inks or writing instrument inks, but all other resins and high Molecules dissolved in water or organic solvents can be used. Resins and polymers that can be used include cellulose derivatives such as ethyl cellulose, hydroxyethyl cellulose, and acetyl cellulose, polyvinyl chloride, polyvinyl complex, polyacrylic acid ester, polyvinyl alcohol, polyvinyl butyral, polyamide, ketone resin, terpene resin, and rosin. or its derivatives, gelatin, gum arabic, etc., and usable solvents include:
Examples include water, alcohols, ketones, esters, aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. In addition, in this invention, additives such as a dispersant to improve the dispersion of pigments, a plasticizer to improve printability, and titanium oxide, zinc white, etc. to increase the hiding power of the coating film are added as necessary. White pigments etc. can be added. To prepare the composition of the present invention, per 100 parts by weight of the composition (hereinafter "parts by weight" is simply referred to as "parts"), 5 to 25 parts of a color former, preferably 10 to 20 parts, and 5 to 25 parts of a color developer.
parts, preferably 10 to 20 parts, resin or polymer 2 to 80 parts
parts, preferably 5 to 20 parts, and 40 to 85 parts, preferably 50 to 75 parts of solvent are mixed. If the color former and color developer are each in excess of 25 parts, the adhesion of the composition to the painted surface will be reduced, and if each is less than 5 parts, the discoloration will become unclear. If the amount of the resin or polymer is more than 80 parts, the viscosity will increase, resulting in poor printability or writability, and if it is less than 2 parts, the adhesiveness of the composition to the coated surface will be reduced. If the amount of solvent is in excess of 85 parts, the adhesion to the coated surface will decrease, and if it is less than 40 parts, the viscosity will increase and the suitability for printing or writing will decrease. To prepare a composition from these components, first heat, melt, and mix the color former and color developer to form a uniform melt, then cool and pulverize to a size of 10 μm or less using a mortar, ball mill, or other means. Use as a color change agent. On the other hand, the resin or polymer is dropped into a solvent, or an additive is added thereto, and if necessary, the mixture is heated and stirred to form a uniform solution, which is then used as a vehicle. Next, a color change agent and, if necessary, a white pigment are added to the vehicle and kneaded by means such as a roll or ball mill to obtain a uniform composition. Next, examples will be described to further clarify this invention. Example 1 7 parts of ferric stearate and 7 parts of phenyl salicylate were placed in a glass container and melted by heating at 100°C on an oil bath.
After cooling, it was crushed in a mortar to obtain a uniform color change agent. To 72 parts of toluene, 8 parts of ethyl cellulose (manufactured by Dow Chemical, trade name: Ethocel 45 cps.) and 2 parts of castor oil were added and stirred at room temperature to form a homogeneous solution to obtain a vehicle. To 82 parts of the vehicle, 14 parts of the color change agent, and 4 parts of titanium oxide were added and thoroughly kneaded using three rolls to obtain an orange thermochromic composition for silk screen printing. The print obtained by silk screen printing this composition on Kent paper was orange in color, but when heated to 65-70°C, the color clearly changed to black-red. When heating was stopped after the color changed, the color quickly returned to its original orange color. Examples 2 to 9 Examples 2 to 9 shown in the attached table were prepared according to Example 1.

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Claims (1)

[Scope of Claims] 1. A thermochromic composition characterized in that a ferric salt of an aliphatic monocarboxylic acid, and monooxybenzoic acid and/or monooxybenzoic acid ester are dissolved or dispersed in a vehicle.