JP7117966B2 - Photochromic pigment and method for producing the same - Google Patents

Description

The present invention relates to photochromic pigments and methods for producing the same.

Photochromic pigments are pigments that have the property of reversibly changing color upon irradiation with light (photochromic properties). Such photochromic pigments are widely used as materials constituting cosmetics, and various types of photochromic pigments have been proposed.

Patent Document 1 discloses an ultraviolet shielding agent comprising a photochromic powder containing anatase-type titanium oxide and iron oxide and having an average particle size of 0.3 to 1 μm.

Patent Literature 2 discloses a photochromic UV-shielding powder containing, as a main component, a powder having a specific surface area of 25 m ² /g or more and a given photochromic property.

JP 2014-169234 A JP-A-4-364117

Photochromic pigments containing titanium oxide and iron oxide, such as the photochromic powder described in Patent Document 1, are known to exhibit a light red color due to the inherent color of iron oxide.

When such colored photochromic pigments are used to produce lighter colors, it is possible to reduce the pigment content and/or the iron oxide content. will decrease. It is also conceivable to mix a white pigment to create a light color, but this has the problem of lowering the photochromic function.

The photochromic UV-shielding powder of Patent Document 2 is considered to be unable to obtain sufficient shielding properties due to the small primary particle size associated with its large specific surface area.

Therefore, there is a need to provide lighter colored photochromic pigments while maintaining similar hiding and photochromic properties as colored photochromic pigments.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and completed the present invention. That is, the present invention is as follows:
<<Aspect 1>> A photochromic pigment,
Based on the total weight of the photochromic pigment, 99.0 to 99.9% by weight of TiO ₂ and 0.1 to 1.0% by weight of Fe ₂ O ₃ are contained,
The average particle diameter of the photochromic pigment measured by a laser diffraction/scattering method is 1 to 20 μm, and the average primary particle diameter of the photochromic pigment measured by a field emission scanning electron microscope is 10 to 100 nm. or a specific surface area according to JIS Z 8830 of 1 to 20 m ² /g,
Photochromic pigment.
<<Aspect 2>> 0.3 parts by mass of the photochromic pigment, 0.25 parts by mass of the colorless transparent resin binder, and 1.75 parts by mass of the solvent component were mixed to prepare a composition, which was placed on a transparent film to a thickness of 18 g. /m ² and stored in a dark place for 24 hours, the lightness L ^* in the L ^* a ^* b ^* color system conforming to JIS Z 8781 of the composition is 80 or more. and |a ^* | is 5 or less, and |b ^* | is 10 or less.
<<Mode 3>> 0.3 parts by mass of the photochromic pigment, 0.25 parts by mass of the colorless transparent resin binder, and 1.75 parts by mass of the solvent component were mixed to prepare a composition, which was placed on a transparent film to a thickness of 18 g. / m ² and stored in a dark place for 24 hours, the color difference ΔE ^* before and after irradiation with ultraviolet rays with a wavelength of 302 nm for 1 minute using a 6 W ultraviolet lamp is 1 or more. A photochromic pigment according to aspect 1 or 2.
<<Aspect 4>> Mixing an aqueous titania sol solution and an aqueous iron nitrate solution to prepare a composite hydrate,
adding an alkali to the composite hydrate to prepare a pigment precursor; and drying the pigment precursor and pulverizing the obtained solid content in an organic solvent to an average particle size of 1 to 20 μm. and calcining to obtain a photochromic pigment,
The photochromic pigment contains 99.0-99.9% by weight TiO ₂ and 0.1-1.0% by weight Fe ₂ O ₃ ,
A method for producing a photochromic pigment.

According to the present invention, it is possible to provide lighter colored photochromic pigments while maintaining the same hiding and photochromic properties as colored photochromic pigments.

《Photochromic Pigments》
The photochromic pigment of the present invention is
Based on the total weight of the photochromic pigment, it contains 99.0 to 99.9% by weight of TiO ₂ and 0.1 to 1.0% by weight of Fe ₂ O ₃ ,
The average particle diameter of the photochromic pigment measured by a laser diffraction/scattering method is 1 to 20 μm, and the average primary particle diameter of the photochromic pigment measured by a field emission scanning electron microscope is 10 to 100 nm, Or the specific surface area according to JIS Z 8830 is 1 to 20 m ² /g.

The inventors have found that the photochromic pigment having the above composition can be a white photochromic pigment. While not wishing to be bound by theory, it is believed that pigment particles having a small average primary particle size form secondary particles that are moderately agglomerated to a relatively large average particle size, resulting in secondary It is considered that the iron oxide molecules are not exposed on the surface of the secondary particles, and as a result, the titanium dioxide has a unique white color.

Here, in the present invention, "white" means a composition prepared by mixing 0.3 parts by mass of a photochromic pigment, 0.25 parts by mass of a colorless transparent resin binder, and 1.75 parts by mass of a solvent component. was coated on a ^transparent film at a thickness of 18 g / m ² and stored in a ^{dark place} for 24 hours. It means that the lightness L ^* is 80 or more, |a ^* | is 5 or less, and |b ^* | is 10 or less.

In this specification, |a ^* | and |b ^* | mean the absolute values of a ^* and b ^* , respectively.

In this case, a polyester-vinyl chloride-vinyl acetate copolymer can be used as the colorless transparent resin binder. The mass of the colorless and transparent resin binder mentioned above means the mass of the solid content.

As the solvent component, a mixed solvent obtained by mixing methyl ethyl ketone and toluene in equal masses in addition to the solvent component contained in the colorless transparent resin binder as a solvent component can be used.

The lightness L ^* can be, for example, 80 or more, 81 or more, 82 or more, or 83 or more, and can be 100 or less, 95 or less, 93 or less, 90 or less, or 88 or less.

The above |a ^* | can be 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less, and can be 0 or more, or greater than 0.

|b ^* | above can be 10 or less, or 9 or less; It can be 8 or more.

In the present invention, the term “photochromic” means that the color difference ΔE ^* before and after irradiation with ultraviolet rays having a wavelength of 302 nm for 1 minute using a 6 W ultraviolet lamp is 1 or more in the above state. is. This color difference ΔE ^* can be, for example, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, or 6 or more, and 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 7 or less. can be.

As the 6 W UV lamp used for UV irradiation, for example, Handheld UV Lamp, 6 W, UVM-57 available from Analytik Jena can be used.

The content of _TiO2 is 99.0% by weight or more, more than 99.0% by weight, 99.1% by weight or more, 99.2% by weight or more, 99.3% by weight, based on the total weight of the photochromic pigment. or more, or 99.4% by mass or more, and may be 99.9% by mass or less, 99.8% by mass or less, 99.7% by mass or less, or 99.6% by mass or less.

The content of Fe ₂ O ₃ is 0.1% by mass or more, 0.2% by mass or more, 0.3% by mass or more, or 0.4% by mass or more, based on the total mass of the photochromic pigment. well, and may be 1.0% by weight or less, less than 1.0% by weight, 0.9% by weight or less, 0.8% by weight or less, 0.7% by weight or less, or 0.6% by weight or less.

The average particle size of the photochromic pigment measured by a laser diffraction/scattering method is 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, 9 μm or more, or 10 μm or more. well, and may be 20 μm or less, 17 μm or less, 15 μm or less, 14 μm or less, 13 μm or less, 12 μm or less, or 11 μm or less. As used herein, the average particle size means the median size (D50) calculated on a volume basis in the laser diffraction/scattering method.

The average primary particle size of the photochromic pigment measured by a field emission scanning electron microscope may be 10 nm or more, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, or 55 nm or more, and may be 100 nm or less, 90 nm or less, or 80 nm. Below, it may be 70 nm or less, or 60 nm or less.

The specific surface area of the photochromic pigment conforming to JIS Z 8830 is 1 m ² /g or more, 2 m ² /g or more, 3 m ² /g or more, 4 m ² /g or more, 5 m ² /g or more, 6 m ² /g or more, or 7 m ² /g or more, and 20 m ² /g or less, 17 m ² /g or less, 15 m ² /g or less, 12 m ² /g or less, 11 m ² /g or less, 10 m ² /g or less, 9 m ² /g or less, or 8 m ² /g or less. This specific surface area can be measured, for example, by the BET flow method.

《Mixed photochromic pigment》
A mixed photochromic pigment contains a white photochromic pigment and a colored photochromic pigment. As the white photochromic pigment, the above white photochromic pigment can be used.

<Colored photochromic pigment>
A colored photochromic pigment is prepared by mixing 0.3 parts by weight of a photochromic pigment, 0.25 parts by weight of a colorless and transparent resin binder, and 1.75 parts by weight of a solvent component to prepare a composition, which is applied to a thickness of a transparent film. After coating at 18 g/m ² and storing this in a ^dark place for 24 ^{hours , |a* |} or |b ^* | is greater than 10. As such colored photochromic pigments, known pigments can be used. For example, PHOTOLITE PK-S and PHOTOLITE LY-S commercially available from Yamaguchi Mica Co., Ltd. can be used.

The lightness L ^* in the L ^* a ^* b ^* color system is, for example, 0 or more, 10 or more, 20 or more, 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, 75 or more, 80 or more, 81 or more. , 82 or greater, or 83 or greater, and may be 100 or less, 95 or less, 93 or less, 90 or less, or 88 or less.

The above |a ^* | can be greater than 5, or 6 or greater, and can be 30 or less, 25 or less, 20 or less, 18 or less, or 15 or less.

The above |b ^* | can be greater than 10, or 12 or greater, and can be 30 or less, 25 or less, 20 or less, 18 or less, or 15 or less.

Further, the colored photochromic pigment may have a color difference ΔE ^* of 1 or more before and after being irradiated with ultraviolet rays having a wavelength of 302 nm for 1 minute using a 6 W ultraviolet lamp. This color difference ΔE ^* can be, for example, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, or 6 or more, and 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 7 or less. can be

<<Method for producing photochromic pigment>>
The method of the present invention for producing photochromic pigments comprises:
mixing an aqueous titania sol solution and an aqueous iron nitrate solution to produce a composite hydrate;
adding an alkali to the composite hydrate to prepare a pigment precursor; and drying the pigment precursor, pulverizing the obtained solid content in an organic solvent, and calcining to produce a photochromic pigment. Including getting.

By the above method, the photochromic pigment has a small average primary particle size, more specifically an average primary particle size of 10 to 100 nm, and a large average particle size, more specifically an average particle size of 1 to 20 μm. can bring.

The method of the present invention preferably includes drying the pigment precursor to remove the organic solvent before firing, from the viewpoint of suppressing the thermal energy required for firing.

<Preparation of composite hydrate>
The composite hydrate is prepared by mixing an aqueous titania sol solution and an aqueous iron nitrate solution.

<Preparation of pigment precursor>
Preparation of the pigment precursor is carried out by adding an alkali to the composite hydrate. From the viewpoint of uniformity, it is preferable to add the alkali in the form of an aqueous alkali solution.

Alkali means salts of alkali metals or alkaline earth metals that exhibit basic properties when dissolved in water. Examples of such alkali include hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide and barium hydroxide, carbonates such as calcium carbonate and sodium carbonate, and the like.

<Pulverization>
Pulverization is carried out by drying the pigment precursor and pulverizing the obtained solid content in an organic solvent to an average particle size of 1 to 20 μm.

As the organic solvent, for example, ethyl acetate, methyl ethyl ketone, toluene, isopropyl alcohol, ethanol, methanol and the like can be used singly or in combination.

A specific mode of pulverization includes, for example, pulverizing the pigment precursor dispersed in an organic solvent with a ball mill so that the average particle size of the pigment precursor becomes 1 to 20 μm. As the ball used in the ball mill, for example, a zirconia ceramic ball having a diameter of 10 mm can be used.

<Baking of pigment precursor>
Firing can be performed at 800° C. or higher, 850° C. or higher, 900° C. or higher, 910° C. or higher, 920° C. or higher, or 930° C. or higher. It can be carried out at 960° C. or lower, or 950° C. or lower.

<<Method for producing mixed photochromic pigment>>
The method of the present invention for making photochromic pigments can include mixing a white photochromic pigment with a colored photochromic pigment to make a mixed photochromic pigment.

EXAMPLES The present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these.

<<Preparation of photochromic pigment>>
<Example 1-1>
125 g of water was added to 200 g of acidic titania sol (content of titanium oxide: 65 g), heated to 80° C. with stirring, and 1.5 g of iron nitrate dissolved in 100 g of water was added.

11.5 g of sodium carbonate dissolved in 700 g of water was gradually added dropwise thereto and stirred for 30 minutes. The pH at that time was 6.5. Then, the precipitated solid was repeatedly washed with water to remove the water-soluble component to obtain a pigment precursor. Next, this was dried at 140° C. to remove moisture, and 100 g of the obtained solid content and 100 g of ethanol were mixed in a 500 ml polypropylene cylindrical container, and a 10 mm diameter zirconia ceramic ball was added thereto, The powder was pulverized and sized with a ball mill until the average particle size was 10 μm. Then, it was dried at 100° C. to remove ethanol and calcined at 940° C. for 3 hours to obtain a photochromic pigment of Example 1-1.

<Comparative Examples 1-1 to 1-2>
PHOTOLITE LY-S and PHOTOLITE PK-S (Yamaguchi Mica Co., Ltd.) were used as photochromic pigments in Comparative Examples 1-1 and 1-2, respectively.

<Measurement of physical properties>
(composition analysis)
A composition analysis of each photochromic pigment was performed using ZSX Primus III+ (Rigaku). Specifically, 5 g of each photochromic pigment was sampled, filled in a dedicated resin holder, and covered with a film to obtain pellets for compositional analysis. A composition analysis was performed using this composition analysis pellet.

(Measurement of average particle size)
Each photochromic pigment was put into a 0.2% solution of sodium hexametaphosphate and dispersed with ultrasonic waves (300 W) for 3 minutes to obtain a dispersion. The average particle size of this dispersion liquid was measured with a refractive index of 2.40 using MICROTRAC MT3000 (manufactured by Microtrac Bell).

(Measurement of average primary particle size)
Each photochromic pigment was placed on the carbon paste, Pt sputtered (E-1045 type ion spatter manufactured by Hitachi), and processed with ZoneSEM (manufactured by Hitachi High-Technologies Corporation).

Then, the average primary particle size of each treated photochromic pigment was measured using an FE-SEM (manufactured by Hitachi High-Technologies Corporation: model number SU8020) under the conditions of an acceleration voltage of 1 Kev and a magnification of 200 k.

(Measurement of specific surface area)
The specific surface area of the photochromic pigment of Example 1-1 was measured by the BET flow method according to JIS Z8830 using HM model-1208 (manufactured by Mountec).

"evaluation"
<Measurement of L ^* a ^* b ^* values>
0.3 parts by mass of each photochromic pigment, 1 part by mass of polyester-vinyl chloride-vinyl acetate copolymer (solid content: 25%) as a colorless transparent resin binder, and methyl ethyl ketone and toluene as solvent components are mixed in equal mass. 1 part by mass of the mixed solvent obtained above was mixed to prepare an ink composition. The parts by mass of the photochromic pigment, the colorless transparent resin binder, and the solvent component in the ink composition were 0.3 parts by mass, 0.25 parts by mass, and 1.75 parts by mass, respectively.

Each prepared ink composition was applied onto a polyethylene terephthalate film (125 μm) using a #34 wire bar (thickness: about 18 g/m ² ) and stored in the dark for 24 hours. After storage, the L ^* a ^* b ^* value of the coating film was measured with a colorimeter (SpectroEye manufactured by x-rite) with a white backing.

Next, the coating film was irradiated with ultraviolet rays having a wavelength of 302 nm for 1 minute using a 6 W ultraviolet lamp (Handheld UV Lamp, 6 W, UVM-57, Analytik Jena), and then the L ^* a ^* b ^* value of the coating film was measured. It was measured. Using the difference in the L ^* a ^* b ^* values obtained, the color difference ΔE ^* before and after one minute of UV irradiation was calculated.

Table 1 shows the configurations and evaluation results of Examples and Comparative Examples.

From Table 1, it can be seen that the ink containing the photochromic pigment of Example 1-1 having an average particle size in the range of 1 to 20 μm and an average primary particle size in the range of 10 to 100 nm was used before irradiation with ultraviolet rays. , lightness L ^* is 80 or more, |a ^* | is 5 or less, and |b ^* | On the other hand, the inks containing the photochromic pigments of Comparative Examples 1-1 and 1-2 are colored because |a ^* | is greater than 5 and |b ^* | is greater than 10. is recognized. In addition, the ink containing the photochromic pigment of Example 1-1 has the same color difference ΔE ^* value as the ink containing the photochromic pigment of Comparative Example 1-1. It had photochromic properties equivalent to those of inks containing organic pigments.

<<Evaluation of mixed photochromic pigment>>
As pigments A to C, the following pigments were prepared.
Pigment A: Photochromic pigment of Comparative Example 1-2 Pigment B: Titanium oxide (Tipaque CR-50, Ishihara Sangyo Co., Ltd.)
Pigment C: Photochromic pigment of Example 1-1

<Reference example>
0.2 parts by mass of the photochromic pigment of Comparative Example 1-2 was mixed with 1 part by mass of a polyester-vinyl chloride-vinyl acetate copolymer (solid content: 25%) as a colorless transparent resin binder, and methyl ethyl ketone and toluene as solvent components. was mixed with 1 part by mass of a mixed solvent obtained by mixing equal masses of the above to prepare an ink composition. The parts by mass of the photochromic pigment, the colorless transparent resin binder, and the solvent component in the ink composition were 0.2 parts by mass, 0.25 parts by mass, and 1.75 parts by mass, respectively.

Each prepared ink composition was applied onto a polyethylene terephthalate film (125 μm) using a #34 wire bar (thickness: about 18 g/m ² ) and stored in the dark for 24 hours. After storage, the L ^* a ^* b ^* value of the coating film was measured with a colorimeter (SpectroEye manufactured by x-rite) with a white backing and a black backing.

Next, the coating film was irradiated with ultraviolet rays having a wavelength of 302 nm for 1 minute using a 6 W ultraviolet lamp (Handheld UV Lamp, 6 W, UVM-57, Analytik Jena), and then the L ^* a ^* b ^* value of the coating film was measured. It was measured. Using the difference in the L ^* a ^* b ^* values obtained, the color difference ΔE ^* before and after one minute of UV irradiation was calculated.

<Comparative Examples 2-1 to 2-2 and Example 2-1>
Inks containing the mixed photochromic pigments of Comparative Examples 2-1 to 2-2 and Example 2-1 in the same manner as in Reference Example, except that the parts by mass of each pigment were changed as shown in Table 1. was made. These samples were also evaluated in the same manner as in the reference example.

Table 2 shows the configurations and evaluation results of Examples, Comparative Examples, and Reference Examples.

From the L ^* a ^* b ^* values in Table 2, the inks containing the mixed photochromic pigments of Example 2-1 and Comparative Examples 2-1 and 2-2 are all higher than the inks containing the pigments of Reference Examples. It can be seen that the color is light.

Further, when comparing Comparative Example 2-1 and Reference Example, in Comparative Example 2-1 in which the content of the colored photochromic pigment was simply reduced, the color was lighter, but the color difference ΔE ^* was significantly reduced. Therefore, it can be understood that the photochromic property is significantly lowered. In addition, when the content of the colored photochromic pigment is simply reduced, the lightness L ^* is significantly reduced when evaluated on a black mount, suggesting that the hiding power of the photochromic pigment is also reduced. can be understood.

Further, when comparing Comparative Example 2-2 with Reference Example, in Comparative Example 2-2 in which part of the colored photochromic pigment was replaced with a white pigment, the lightness L ^* increased when evaluated on a black mount. However, since the color difference ΔE ^* is significantly reduced, it can be understood that although the hiding property is better than that of the reference example, the photochromic property is still significantly reduced.

On the other hand, when Example 2-1 is compared with Reference Example, the ink containing the mixed photochromic pigment of Example 2-1, which is a combination of a white photochromic pigment and a colored photochromic pigment, has good hiding properties. and good photochromic properties can be maintained.

Claims (5)

A photochromic pigment,
Based on the total weight of the photochromic pigment, 99.0 to 99.9% by weight of TiO ₂ and 0.1 to 1.0% by weight of Fe ₂ O ₃ are contained,
The average particle diameter of the photochromic pigment measured by a laser diffraction/scattering method is 1 to 20 μm, and the average primary particle diameter of the photochromic pigment measured by a field emission scanning electron microscope is 10 to 100 nm. ,
Photochromic pigment. 2. The photochromic pigment according to claim 1, having a specific surface area according to JIS Z 8830 of 1 to 20 m ² /g. 0.3 parts by mass of the photochromic pigment, 0.25 parts by mass of the colorless and transparent resin binder, and 1.75 parts by mass of the solvent component were mixed to prepare a composition, which was coated on a transparent film to a thickness of 18 g/m ² . After being coated and stored in a dark place for 24 hours, the composition has a lightness L ^* of 80 or more in the L ^* a ^* b ^* color system according to JIS Z 8781, | 3. The photochromic pigment according to claim 1, wherein a ^* | is 5 or less and |b ^* | is 10 or less. 0.3 parts by mass of the photochromic pigment, 0.25 parts by mass of the colorless and transparent resin binder, and 1.75 parts by mass of the solvent component were mixed to prepare a composition, which was coated on a transparent film to a thickness of 18 g/m ² . After being coated and stored in a dark place for 24 hours, the color difference ΔE ^* before and after irradiation with ultraviolet rays having a wavelength of 302 nm for 1 minute using a 6 W ultraviolet lamp is 1 or more. 4. The photochromic pigment according to any one of 3 . mixing an aqueous titania sol solution and an aqueous iron nitrate solution to produce a composite hydrate;
adding an alkali to the composite hydrate to prepare a pigment precursor; and drying the pigment precursor and pulverizing the obtained solid content in an organic solvent to an average particle size of 1 to 20 μm. and calcining to obtain a photochromic pigment,
The photochromic pigment contains 99.0-99.9% by weight TiO ₂ and 0.1-1.0% by weight Fe ₂ O ₃ ,
A method for producing the photochromic pigment according to any one of claims 1 to 4 .