JPH0823008B2 - Microencapsulated photochromic material, its manufacturing method and aqueous ink composition using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a microencapsulated photochromic material and a method for producing the same, and more particularly to a microencapsulated photochromic material having excellent durability and a method for producing the same.

The present invention further relates to a water-based ink composition using the above microencapsulated photochromic material.

[Background Art] Inorganic silver halide as a photochromic compound,
These include sodalite, organic anils, spiropyrans, spirooxazines, metal cytizonates, phenothiazines, phenozines, and pianthrones. Among these, spirooxazine compounds are particularly well-suited for repeated coloring and decoloring. However, to maintain rapid coloring, decoloring reversibility, color tone, and color density over a long period of time, they require protection from atmospheric oxygen, harmful vapors, and harmful light. For this reason, photochromic materials have traditionally been produced and used using extremely complicated methods, such as dispersing spirooxazine compounds in a resin material and then laminating them with a thick plastic film for protection, or dispersing them in a resin material, hardening them, pulverizing them, and then coating them with an inorganic protective material.

As described above, conventional photochromic materials containing spirooxazine compounds have the problem that the production method is complicated, which inevitably leads to high costs, and furthermore, the durability is insufficient.

[Disclosure of the Invention] The present invention provides a method for producing a microcapsule comprising a crosslinked gelatin-based film agent, the method comprising: dissolving a spirooxazine compound having a boiling point of 40 to 160°C and a solubility in water (20°C) of 100% or less;
The present invention relates to a microencapsulated photochromic material characterized in that the material is encapsulated in a solution containing a solvent in which the content of the compound is 15 wt % or less.

The microencapsulated photochromic materials of the present invention will now be described in detail.

Examples of spirooxazine compounds include compounds of the following general formula [I]: (In the formula, ^R1 , ^R2 , and ^R3 represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a cycloalkyl group, or an aryl group, and ^R2 and ^R3 may be bonded to each other to form a ring. ^R4 represents a hydrogen atom or a cyclic group having 1 to 10 carbon atoms.)
R1 represents an alkyl group of 5, and ^R2 may have another spirooxazine ring connected via an alkylene or arylene group, forming a dimeric compound as a whole. Rings X and Y represent an optionally substituted hydrocarbon aromatic ring or heteroaromatic ring. Z represents an oxygen atom or a sulfur atom.) is used.

In the compound represented by the above formula [I], ^R1 , ^R2 and ^R3 are each an alkyl group such as an alkyl group having 1 to 28 carbon atoms, an alkoxyalkyl group such as a methoxyethyl group and an ethoxyethyl group, an alkoxyalkoxyalkyl group such as a methoxyethoxyethyl group and an n-butoxyethoxyethyl group, an alkoxyalkoxyalkoxyalkyl group such as a methoxyethoxyethoxyethyl group and an ethoxyethoxyethoxyethyl group, an aryloxyalkyl group which may be substituted such as a phenyloxyethyl group, a naphthyloxyethyl group and a p-chlorophenyloxyethyl group, an aryloxyalkyl group which may be substituted such as a benzyl group, a phenethyl group, a p-chlorobenzyl group and a p-nitrobenzyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclopentyl group, Examples of the cycloalkylalkyl group include methyl, optionally substituted alkenyloxyalkyl groups such as allyloxyethyl and 3-bromoallyloxyethyl; cyanoalkyl groups such as cyanoethyl and cyanomethyl; hydroxyalkyl groups such as hydroxyethyl and hydroxymethyl; tetrahydrofurfurylalkyl groups such as tetrahydrofurylethyl; substituted or unsubstituted alkyl groups such as allyl and 2-chloroallyl; substituted or unsubstituted aryl groups such as phenyl, p-methylphenyl, naphthyl, and m-methoxyphenyl; and cycloalkyl groups such as cyclohexyl and cyclopentyl. ^R and ^R may be linked together to form a cycloalkyl group such as cyclohexyl, cyclopentyl, or cycloheptyl. ^R may also be linked to another spirooxazine ring via an alkylene or arylene group to form a dimeric compound. ^R represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, such as methyl or ethyl.

The optionally substituted hydrocarbon aromatic ring or heteroaromatic ring of rings X and Y includes a benzene ring, a naphthalene ring,
Examples of substituents on these rings include halogen atoms such as chlorine atoms, bromine atoms, and iodine atoms, alkyl groups having 1 to 6 carbon atoms, alkoxy groups, alkoxycarbonyl groups, alkoxysulfonyl groups such as methoxysulfonyl groups and ethoxysulfonyl groups, cyano groups, amino groups, dimethylamino groups, and nitro groups.

In the present invention, among the spirooxazine compounds represented by the above formula [I], the spirooxazine compounds represented by the following general formula [II] (wherein ^R1 is an alkyl group or alkoxyalkyl group having 1 to 20 carbon atoms, ^R4 is a hydrogen atom or a methyl group, and X and Y are an optionally substituted hydrocarbon aromatic ring or a heteroaromatic ring) is preferably used.

The solvent used in the present invention has a boiling point of 40 to 160°C and a solubility in water (20°C) of 15 wt% or less. Solvents with lower boiling points are prone to volatilization and are therefore difficult to microencapsulate, while solvents with higher boiling points are undesirable because the spirooxazine compound does not dissolve in them and is prone to deterioration. Furthermore, the solvent has a high solubility in water (15 wt%).
The solvent dissolves in water, causing the spirooxazine compound to float, making it difficult to microencapsulate. Preferred solvents include ketone solvents such as cyclohexanone and methyl isobutyl ketone; hydrocarbon aromatic ring solvents such as toluene and benzene; tetrachloroethylene, tetrachloroethane, trichloroethylene;
Examples of the solvent include halogenated hydrocarbon solvents such as methylene chloride; and ester solvents such as butyl acetate, with methyl isobutyl ketone, cyclohexanone, toluene, benzene, and trichloroethylene being particularly preferred.

The method for producing the microencapsulated photochromic material of the present invention is to use a spirooxazine compound having a boiling point of 40 to 1000 .
The process involves dissolving the material in a solvent at 160°C that has a solubility in water (20°C) of 15 wt% or less, and then incorporating the resulting material into microcapsules made of a cross-linked gelatin-based film agent. During or after the process, most of the solvent is evaporated from the capsules, leaving only a trace amount of solvent.

Various methods are used for microencapsulation, such as phase separation, interfacial polymerization, and submerged drying. However, encapsulation using gelatin phase separation is the most suitable method because it involves the step of volatilizing the solvent.

The phase separation method uses a water-soluble polymer as the capsule wall material, and then phase separates (coacervates) the concentrated polymer solution from the aqueous solution to create the capsule wall. This method is commonly called the coacervation method, and uses coacervates as the capsule wall. There are two methods for forming coacervates: simple coacervation, in which hydrophilic polymers precipitate and undergo phase separation by adding salt, alcohol, acetone, etc.; and complex coacervation, in which two or more hydrophilic polymers with opposite charges undergo phase separation by adjusting pH and dilution with water. Complex coacervation is preferred for practical purposes.

The general manufacturing methods using complex coacervation are broadly divided into the following three types.

1) Emulsification or dispersion process 2) Coacervation process 3) Hardening process Known wall film insolubilizing (hardening) agents for hardening process 3) include aldehydes, diketones, epoxides, acid anhydrides, acid chlorides, carbodiimides, inorganic salts, etc. Among aldehydes, dialdehydes are known to have high hardening speed and
Glutaraldehyde is particularly preferred in terms of color density upon irradiation with light and its effect on the light resistance of printed matter.

As the microencapsulated film agent, a crosslinked gelatin film agent is used in view of the light resistance and color density of the photochromic material. Among gelatin-based film agents, preferred are gelatin-gum arabic film agents and gelatin-carboxymethyl cellulose film agents.

In the present invention, microencapsulation with a crosslinked gelatin membrane can be carried out, for example, as follows.

In the coacervation method, a solution of a spirooxazine compound, which is the core substance of the photochromic material, is first mixed with an aqueous gelatin solution to emulsify it, and then aqueous solutions of carboxymethyl cellulose, gum arabic, etc. are mixed to cause complex coacervation. Next, 5 to 20 wt % of a hardener is added to the gelatin, and the mixture is stirred for a predetermined period of time. For example, when an aldehyde is used as the hardener, the mixture is usually stirred at a temperature of 5 to 20°C for 1 hour.
Stirring can be carried out for up to 20 hours.

Furthermore, in order to improve light resistance, the microencapsulated photochromic material of the present invention may contain an ultraviolet absorber, an antioxidant, and a hindered amine stabilizer at the time of dissolving the spirooxazine compound in a solvent, in amounts that do not affect color development. The ultraviolet absorber may also be incorporated into the capsule wall.

Particularly suitable ultraviolet absorbers have an effective absorption wavelength of 300 nm or less, and are, for example, of the chemical structure These include, among others, is preferred.

On the other hand, antioxidants include those with the following chemical structure: In addition, phosphorus-based antioxidants include those represented by the following structural formula:

Particularly suitable hindered amine stabilizers include, for example: The various additives are added to the solution in the microcapsules, and the amount of the additives used is usually 20% or more and about the same amount as the photochromic material.

The ultraviolet absorber having an effective absorption wavelength of 300 nm or less may be mixed into the microcapsule wall in the form of fine particles or fine oil droplets dissolved in a solvent.

The present invention also provides an aqueous ink composition comprising an aqueous medium, a colorant, and a vehicle as main components, wherein the colorant is a spirooxazine compound having a boiling point of 40 to 160°C, contained in a microcapsule comprising a crosslinked gelatin film agent.
The present invention relates to an aqueous ink composition characterized in that the ink composition is a solution containing a solvent having a temperature of 0.1°C and a solubility in water (20°C) of 15 wt% or less, and that the ink composition uses an aqueous emulsion resin as a vehicle and has a pH of 5 or higher.

In the ink composition of the present invention, a spirooxazine compound is used as the photochromic compound, which is an excellent photochromic compound in terms of coloring/decoloring speed and durability against repeated use.

Furthermore, spirooxazine compounds represented by the above structural formula are more preferred.

When preparing a water-based ink composition, a water-based emulsion resin is used as the vehicle so that the pH of the ink composition after preparation is 5 or higher, and examples thereof include acrylic or urethane homopolymers or copolymers.

Specifically, various acrylic copolymer resins are used, including Yodosol A-4100, MR96, LD1009,
A-4540, A-7000, AA-11 (all manufactured by Kanebo NSC Co., Ltd.), Seika Plain 100, 120, 200 (all manufactured by Dainichi Seika Chemicals Co., Ltd.), HD-3 (manufactured by Toa Gosei Chemical Industry Co., Ltd.), Jurimer SEK-30
Commercially available products such as 1 and FC-30 (both manufactured by Wako Pure Chemical Industries, Ltd.) can be used.

As the urethane resin, various types can be used, but commercially available products such as Superflex E-2000 and 200 (both manufactured by Daiichi Kogyo Co., Ltd.) can be used.

Of the above, acrylic copolymer resins are particularly preferred.

The pH of the ink composition of the present invention is 5 or higher by using the aqueous emulsion resin described above, but the pH of the ink composition is preferably near neutral, from 5 to 9.
Here, the pH value is a value measured by mixing 10 g of the ink composition with 100 ml of water and stirring at 25°C.) [Best Mode for Carrying Out the Invention] Next, the present invention will be described with reference to examples and test examples, but the present invention is not limited to these.

The light resistance test was conducted by exposing the product to sunlight for an average of 9 hours a day from June to September.
The exposure time was 10 hours. The parts are by weight.

Example 1: Production of Microencapsulated Photochromic Material As a core material, 34 g of methyl isobutyl ketone (boiling point 115.9°C, solubility in water (20°C) 1.8 wt%) and 3 g of a spironaphthoxazine compound represented by the following structural formula were mixed together to prepare a mixture.

The core material was heated to 50°C and the pH was adjusted to 4.75.
The particles were emulsified in 76 ml of gelatin solution to a particle size of 20 μm.
Add 176 ml of 2% gum arabic solution heated to 50°C.
The temperature of this mixture was kept at 50°C, the pH was adjusted to 4.75, and then it was slowly cooled. When the temperature reached 28°C, it was rapidly cooled to 10°C, 2 ml of 25% aqueous glutaraldehyde solution was added, and the mixture was stirred at 10°C for 4 hours. The temperature was then raised to 40°C and the mixture was stirred overnight.

The result was a solution containing microencapsulated photochromic material.

Preparation and Test Examples of Water-Based Ink Compositions The microcapsule-containing liquid obtained above was diluted to 40% by weight.
The liquid phase was removed until the pH reached 5. One part of the resulting microcapsule-containing liquid was mixed with one part of an acrylic copolymer binder (trade name Yodozole A-4100, manufactured by Kanebo NSC Co., Ltd.) to obtain an ink composition. The pH of the ink composition was 5.
The score was 97.

This ink composition was used for screen printing on cotton fabric.
It was dried at 0°C for 5 minutes.

In addition to this encapsulated ink composition, for comparison, a non-encapsulated ink composition and an ink composition which was dissolved in a high boiling point solvent and then encapsulated were also tested for light resistance. The results showed that: - Encapsulated ink composition: Deteriorated after 24 days; - Non-encapsulated ink composition: Deteriorated after 5 hours; - Ink composition which was dissolved in a high boiling point solvent and then encapsulated: Deteriorated after 14 hours (SAS-296, manufactured by Nippon Petrochemicals, was used as the high boiling point solvent).

The light resistance test was conducted in June to September, with the product exposed to sunlight for an average of 9 hours per day.
The same results as above were also obtained in tests using a Shimadzu XF-15D xenon fade tester.

In addition, the color density upon light irradiation was measured using a densitometer TR-92
7 (Macbeth Co.) showed a high OD value of 1.30 and gave a deep blue color.

Regarding the color development and decolorization times of printed matter using this encapsulated ink composition, when exposed to sunlight, the color developed within 3 seconds, and when returned to a dark place, the color also faded within 3 seconds.

Example 2 Toluene (boiling point 110.6°C, solubility in water (20°C) 0.05w) was used as the core material.
t%] 39 g of the same spiro-naphthoxazine compound as in Example 1, 4 g of the same compound as in Example 1, were mixed and adjusted, and encapsulated in the same manner as in Example 1.
The pH of the ink was 5.97. The same lightfastness test as in Example 1 was carried out, and the results were as follows: Encapsulated ink: Deterioration occurred after 25 days Non-encapsulated ink: Deterioration occurred after 5 hours

The color of the encapsulated ink developed within 30 seconds when exposed to sunlight, and faded within 30 seconds when placed in a dark place.

Example 3: Core substance: 34 g of methyl isobutyl ketone (boiling point 115.9°C, solubility in water (20°C) 1.8 wt%); 3 g of the same spiro-naphthoxazine compound as in Example 1; 0.5 g of an ultraviolet absorber (Viosorb 80; Kyodo Pharmaceutical Co., Ltd.) (effective absorption wavelength 240-290 nm); and 0.5 g of a secondary antioxidant (Sumilizer P-16; Sumitomo Chemical Co., Ltd.).
0.7 g of the solution was prepared, encapsulated, and made into ink in the same manner as in Example 1. The pH of the ink was 5.97.

A lightfastness test similar to that in Example 1 was conducted, and the results showed that: Encapsulated ink...after 57 days Non-encapsulated ink...after 10 hours

The coloring and decoloring times of the encapsulated ink were similar to those of Example 1.

Example 4: Example of production of microencapsulated photochromic material. 4.3 g of methyl isobutyl ketone (boiling point 115.9°C, solubility in water (20°C) 1.8 wt%) as wall impurities, 0.1 g of ultraviolet absorber (trade name: Viosorb 80, manufactured by Kyodo Pharmaceuticals) [effective absorption wavelength 240-290 nm], and 0.03 g of ultraviolet absorber (trade name: Sumisorb 400, manufactured by Sumitomo Chemical Co., Ltd.) [effective absorption wavelength 240-290 nm] were prepared, heated to 40°C, the pH was adjusted to 4.75, and emulsified in 10 g of a 5% gelatin aqueous solution to produce emulsion droplets in the gelatin aqueous solution with a particle size of 0.5 μm or less.

Next, 34 g of methyl isobutyl ketone (boiling point 115.9°C, solubility in water (20°C) 1.8 wt%) was mixed to prepare a core material. 3 g of the same spiro-naphthoxazine compound as in Example 1, 0.5 g of an ultraviolet absorber (trade name: Viosorb 80; Kyodo Pharmaceutical Co., Ltd.) (effective absorption wavelength 240-290 nm), and 0.7 g of a secondary antioxidant (Sumilizer P-16; Sumitomo Chemical Co., Ltd.) were mixed together. Using this core material, encapsulation was carried out in the same manner as in Example 1. However, the mixture was heated to 33°C when the temperature reached 28°C, and the gelatin aqueous solution was added. The mixture was then slowly cooled to incorporate the impurities into the gelatin wall. After the mixture reached 28°C, it was rapidly cooled to 10°C, and 2 ml of a 25% glutaraldehyde aqueous solution was added.
After stirring at 40° C. for 4 hours, the temperature of the mixture was raised to 40° C. and stirred for 24 hours. The resulting aqueous solution of microcapsules was filtered to obtain microcapsules.

An ink composition was prepared in the same manner as in Example 1, except that the microcapsules obtained as described above were used. The pH of the ink was 5.97. A print was obtained on cotton fabric using this ink.

This print develops color within 3 seconds of exposure to sunlight.
When the sample was returned to the dark, the color disappeared within 3 seconds.

When a lightfastness test was conducted on printed matter using this ink composition, it took 69 days (1,656 hours) for the ink to deteriorate, demonstrating excellent lightfastness.

The color density upon irradiation was measured using a densitometer TR-927, and the OD value was a high value of 1.52, giving a deep blue color tone.

Example 5 Toluene (boiling point 110.6°C, solubility in water (20°C) 0.05w) was used as the core material.
t%] 39g and a spiro naphthoxazine compound represented by the following structural formula
4g The above ingredients were mixed and prepared, and encapsulated in the same manner as in Example 1.
The liquid phase was removed until it reached 40% of the total weight, thereby obtaining a microcapsule-containing liquid.

Next, an ink composition was prepared in the same manner as in Example 1, except that the above microcapsule-containing liquid was used. The pH of the ink was 5.97. Screen printing was carried out using this ink.

When the screen print of this ink composition is exposed to sunlight, the color develops within 3 seconds. When it is returned to the dark, the color develops in the same way.
The color disappeared within 30 seconds.

When a lightfastness test was conducted on printed matter using this ink composition, it took 42 days (1008 hours) for the ink to deteriorate, demonstrating excellent lightfastness.

Example 6 Core substance: 34 g of methyl isobutyl ketone (boiling point 115.9°C, solubility in water (20°C) 1.8 wt%); 3 g of a spiro-naphthoxazine compound represented by the following structural formula; 0.5 g of an ultraviolet absorber (trade name: Viosorb 80; manufactured by Kyodo Pharmaceuticals) (effective absorption wavelength 240-290 nm); 0.7 g of an antioxidant (Sumilizer P-16; manufactured by Sumitomo Chemical Co., Ltd.) The above ingredients were mixed and prepared, and encapsulated in the same manner as in Example 1.
Microcapsules were obtained.

Next, an ink composition was prepared in the same manner as in Example 1, except that the above microcapsules were used.
The ink was screen printed on cotton fabric.

When the ink composition was screen printed on cotton fabric, it developed color within 3 seconds when exposed to sunlight, and when it was returned to a dark place, it also faded within 3 seconds.

When a lightfastness test was conducted on printed matter using this ink composition, it took 57 days (1,368 hours) for the ink to deteriorate, demonstrating excellent lightfastness.

Example 7 Toluene (boiling point 110.6°C, solubility in water (20°C) 0.05w) was used as the core material.
t%] 39g Spirooxazine compound represented by the following structural formula 4g The ink composition was prepared by encapsulating the ink in the same manner as in Example 1. The pH of the ink was 5.97.

This ink composition was screen printed on cotton fabric and heated at 120°C.
It was dried for 5 minutes.

When the screen print of this ink composition is exposed to sunlight, the color develops within 40 seconds. When it is returned to the dark, the color develops in the same way.
The color disappeared within 40 seconds.

When a lightfastness test was conducted on printed matter using this ink composition, it took 30 days (720 hours) for the ink to deteriorate, demonstrating excellent lightfastness.

Example 8 Microencapsulation was carried out in the same manner as in Example 1, except that the spirooxazine compounds and solvents shown in Table 1 below were used, and then the microencapsulated ink compositions were prepared.
The print was screen printed on cotton cloth, and the results of the lightfastness test of the print are shown in Table 1, which showed excellent lightfastness.

These prints developed color in a short time when exposed to sunlight, and faded in a short time when returned to a dark place, and this change could be repeated.

Example 9: Preparation of Microencapsulated Photochromic Material The same core material as in Example 5 was heated to 50°C and emulsified in 80 ml of a 5% aqueous gelatin solution adjusted to pH 4.75 to a particle size of 20 μm. Then, the emulsion was dissolved in 185 ml of a 2% aqueous gum arabic solution heated to 50°C.
The water temperature was kept at 50°C, the pH was adjusted to 4.75, and then the mixture was slowly cooled. When the water temperature reached 28°C, it was cooled to 10°C, and 5 ml of 37% aqueous formalin solution was added. The mixture was stirred at 10°C for 4 hours. The temperature was then raised to 40°C and the mixture was stirred overnight.

The result was a solution containing microencapsulated photochromic material.

Preparation and Test Examples of Water-Based Ink Compositions The liquid phase was removed from the microcapsule-containing liquid prepared as described above until the weight of the remaining liquid was 40%. One part of the resulting microcapsule-containing liquid was mixed with one part of an acrylic copolymer binder emulsion (trade name Yodosol A-4100, manufactured by Kanebo NSC Co., Ltd.) to obtain an ink composition. The pH of the ink was 5.97. This ink composition was used for screen printing on cotton fabric and dried at 120°C for 5 minutes.

When the screen print of this ink composition is exposed to sunlight, the color develops within 30 seconds. When it is returned to the dark, the color develops in the same way.
The color disappeared within 30 seconds.

When a lightfastness test was conducted on printed matter using this ink composition, it took 42 days (1008 hours) for the ink to deteriorate, demonstrating excellent lightfastness.

The color density upon irradiation was measured using a densitometer TR-927 (Macbeth Co.), and the OD value was a high value of 1.50, giving a deep blue color tone.

Example 10: Preparation of Microencapsulated Photochromic Material The same core material as in Example 6 was heated to 60°C and emulsified in 25 g of acid-treated gelatin dissolved in 440 g of water. 50 g of a 5% aqueous solution of carboxymethylcellulose (etherification degree, average polymerization degree 150) was then added, and the pH was adjusted to 5.5 to form a coacervation. This was cooled to 10°C, and 10 g of 25% glutaraldehyde was added, followed by 10% caustic soda.
H was adjusted to 7.0.

The result was a solution containing microencapsulated photochromic material.

Preparation and Test Examples of Water-Based Ink Compositions The liquid phase was removed from the microcapsule-containing liquid obtained as described above until the weight of the aqueous solution was 40%. One part of the obtained microcapsule-containing liquid was used to prepare an ink in the same manner as in Example 1. The pH of the ink was 5.97. A lightfastness test was conducted, and it took 69 days for the printed matter printed using this ink composition to deteriorate. The color development and decolorization times of the ink composition were as good as those of Example 1.

The color density upon irradiation was measured using a densitometer TR-927 (Macbeth Co.), and the OD value was 1.25, with a deep blue color tone.

Example 11 Microencapsulated ink compositions were obtained in the same manner as in Example 1, except that the spirooxazine compounds of the present invention shown in Table 2 below were used. These were screen printed on cotton cloth and the results of the lightfastness test are shown in Table 2, which showed excellent lightfastness.

These printed materials developed color when exposed to sunlight and faded when returned to a dark place; this change could be repeated, and the color density when exposed to light was also high.

Example 12: The same core material as in Example 5 was used, and encapsulated in the same manner as in Example 1. An ink composition was obtained in the same manner as in Example 1, except that 1 part of Yodozole MR96 (aqueous emulsion of acrylic copolymer resin, manufactured by Kanebo-NSC Co., Ltd.) was used as the vehicle. The pH of this ink composition was 6.15. This ink composition was used to screen print on cotton fabric and dried at 120°C for 5 minutes.

When the screen print of this ink composition is exposed to sunlight, the color develops within 30 seconds. When it is returned to the dark, the color develops in the same way.
The color disappeared within 30 seconds.

When a lightfastness test was conducted on printed matter using this ink composition, it took 42 days (1008 hours) for the ink to deteriorate, demonstrating excellent lightfastness.

Example 13 An ink composition was prepared in the same manner as in Example 1, except that 1 part of Superflex E-2000 (urethane resin emulsion, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as the vehicle. The p value of this ink composition was 5.16. The ink composition was then screen-printed onto cotton fabric and dried at 120°C for 5 minutes.

When the ink composition was screen printed on cotton fabric, it developed color within 3 seconds when exposed to sunlight, and when it was returned to a dark place, it also faded within 3 seconds.

When lightfastness tests were conducted on printed matter using this ink composition, it took 25 days (600 hours) for the ink to deteriorate, demonstrating excellent lightfastness.

Example 14 In Example 1, Julimer SEK-3 was used as a vehicle.
An ink composition was obtained in the same manner as above, except that 1 part of 01 (acrylic resin emulsion, manufactured by Wako Pure Chemical Industries, Ltd.) was used. The pH of this ink composition was 8.00. The ink composition was then screen-printed onto cotton fabric and dried at 120°C for 5 minutes.

When the screen print of this ink composition is exposed to sunlight, the color develops within 10 seconds. When it is returned to the dark, the color develops in the same way.
The color disappeared within 10 seconds.

When lightfastness tests were conducted on printed materials using this ink composition, it took 24 days (576 hours) for the ink to deteriorate, demonstrating excellent lightfastness.

Example 15 In Example 1, Julimer FC-30 was used as a vehicle.
An ink composition was obtained in the same manner as above, except that 1 part of acrylic copolymer resin (manufactured by Wako Pure Chemical Industries, Ltd.) was used.
The pH was 8.69. Next, the resulting solution was screen printed onto a cotton cloth and dried at 120°C for 5 minutes to obtain a printed matter.

When the ink composition was screen printed on cotton fabric, it developed color within 3 seconds when exposed to sunlight, and when it was returned to a dark place, it also faded within 3 seconds.

When lightfastness tests were conducted on printed materials using this ink composition, it took 24 days (576 hours) for the ink to deteriorate, demonstrating excellent lightfastness.

Example 16: Ink compositions were prepared by microencapsulation in the same manner as in Example 1, except that the spirooxazine compounds shown in Table 3 below and aqueous emulsion resins were used as the vehicle. These were screen-printed onto cotton fabric, and the results of the lightfastness test showed excellent lightfastness, as shown in Table 3.

These prints developed color when exposed to sunlight and faded when returned to a dark place, and this change could be repeated.

Example 17 In Example 6, Yoshinox (trade name) was used as the core material of the microcapsules instead of Sumilizer P-16 as an antioxidant.
An ink composition was prepared in the same manner except that 0.7 g of BHT (Yoshitomi Pharmaceutical Co., Ltd.) was used. The pH of the ink was 5.97.

This ink composition was used to screen print on cotton fabric in the same manner as in Example 6, and a lightfastness test was carried out. As a result, it took 59 days (=1416 hours) for the ink to deteriorate.

Example 18 In Example 6, a hindered amine-based light stabilizer [trade name: Sanol LS-26
An ink composition was prepared in the same manner except that 0.5 g of [26; manufactured by Sankyo Co., Ltd.] was added. The pH of the ink was 5.97.

Furthermore, this ink composition was used for screen printing in the same manner as in Example 6, and a lightfastness test was carried out. As a result, it took 68 days (=1632 hours) for the ink composition to deteriorate, demonstrating excellent lightfastness.

Examples 19-20: Preparation of Microencapsulated Photochromic Material As the core material, 34 g of the same solvent, methyl isobutyl ketone, as used in Example 6, and 3 g of spironaphthoxazine were used, and the additives shown in Table 4 below were mixed and adjusted.

Heat the above core material to 60°C, add 25g of acid-processed gelatin and 4g of water.
The solution was emulsified in 40g of 5% carboxymethyl cellulose solution (50g of etherification degree, average polymerization degree 15
The pH was adjusted to 5.5 by adding 25% glutaraldehyde.
10 g was added, and the pH was adjusted to 7.0 with 10% caustic soda.

The result was a solution containing microencapsulated photochromic material.

Preparation and Test Examples of Water-Based Ink Compositions The liquid phase was removed from the microcapsule-containing solution obtained as described above until the weight of the solution was 40% of the total weight. One part of the resulting microcapsule-containing solution was used to prepare ink in the same manner as in Example 1. The pH of each ink was 5.97. The lightfastness test and color density upon light irradiation were performed in the same manner as in Example 1, and the results are shown in Table 4.

Example 22: The same procedure as in Example 1 was repeated except that the spirooxazine compounds and additives shown in Table 5 below were used, and then microencapsulation was carried out in the same manner as in Example 1 to prepare ink compositions, which were then screen-printed onto cotton fabric. The results of the lightfastness test of the prints are shown in Table 5, and the prints showed excellent lightfastness.

These prints developed color in a short time when exposed to sunlight, and faded in a short time when returned to a dark place, and this change could be repeated.

[Industrial Applicability] The microencapsulated photochromic material of the present invention is easy to manufacture and reduces costs due to its simple manufacturing method. Furthermore, the photochromic material obtained by the present invention has dramatically improved light resistance, coloring/fading speed, and storage stability. By adding an ultraviolet absorber and an antioxidant in amounts that do not affect coloring, or by incorporating an ultraviolet absorber into the capsule wall, it is possible to achieve even greater improvement in durability. This has the effect of enabling the material to be widely used in paints, clothing, toys, stationery, sporting goods, cosmetics, sunglasses, window lighting adjustment, optical recording materials, color displays, product monitors where light resistance is an issue, etc.

──────────────────────────────────────────────────── Continued from the front page (31) Priority Number: Patent Application No. 63-263306 (32) Priority Date: October 19, 1988 (33) Priority Country: Japan (JP) (56) References: Patent Application No. 51-87177 (JP, A) Patent Application No. 62-289684 (JP, A) Science Progress Report Coverte, 99 (3430), pp. 14-23, 1971 Solar Energy Materials Als, 14 (3-5), pp. 215-221, 1986

Claims (8)

[Claims] Claim 1: A microcapsule comprising a crosslinked gelatin film agent, in which a spirooxazine compound having a boiling point of 40 to 160°C and a solubility in water (20°C) is incorporated.
2. A microencapsulated photochromic material comprising a photochromic material encapsulated in a solution containing a solvent having a molecular weight of 15 wt % or less. 2. A microencapsulated photochromic material according to claim 1, wherein the solution contains an ultraviolet absorber having an effective absorption wavelength of 300 nm or less. 3. A microencapsulated photochromic material according to claim 1 or 2, wherein the solution contains an antioxidant. 4. A microencapsulated photochromic material according to any one of claims (1) to (3), wherein the solution contains a hindered amine light stabilizer. Claim 5: A spirooxazine compound having a boiling point of 40 to 16
A method for producing a microencapsulated photochromic material, comprising the steps of dissolving the material in a solvent at 0°C and having a solubility in water (20°C) of 15 wt% or less, and incorporating the resulting material into microcapsules made of a crosslinked gelatin-based film agent, and then volatilizing most of the solvent from the microcapsules during or after the process, leaving only a trace amount of solvent. [Claim 6] A method for producing a microencapsulated photochromic material according to claim (5), wherein an ultraviolet absorber having an effective absorption wavelength of 300 nm or less, an antioxidant, or both are added when the spirooxazine compound is dissolved in a solvent. [Claim 7] A method for producing a microencapsulated photochromic material according to claim (5) or (6), wherein fine particles of an ultraviolet absorber or minute oil droplets of an ultraviolet absorber dissolved in a solvent and having an effective absorption wavelength of 300 nm or less are mixed into the microcapsule walls. [Claim 8] An aqueous ink composition whose main components are an aqueous medium, a colorant, and a vehicle, wherein the colorant is contained in microcapsules composed of a crosslinked gelatin-based film agent as a solution containing a spirooxazine-based compound in a solvent having a boiling point of 40 to 160°C and a solubility in water (20°C) of 15 wt% or less, and wherein an aqueous emulsion resin is used as the vehicle, and the pH of the ink composition is 5 or higher.