JP2022122678A - Toner, manufacturing method of toner and image reading method - Google Patents

Abstract

To provide toner with which an invisible image that may have excellent invisibility in a visible light region and may have excellent readability in a near-infrared region can be obtained.SOLUTION: There is provided toner which has a toner particle. The toner contains a gold nanorod. The gold nanorod contains: a gold nanorod A which has a peak in a range of 6.0-13.0 in an aspect ratio in measurement of an aspect ratio distribution; and a gold nanorod B which has a peak in a range of 1.6-2.6 in an aspect ratio in measurement of the aspect ratio distribution. When measuring a light absorption wavelength of the gold nanorod B, the toner has a peak in a range of 580-650 nm.SELECTED DRAWING: None

Description

The present disclosure relates to toners, methods of manufacturing toners, and methods of reading images.

2. Description of the Related Art In recent years, "invisible printing," which embeds invisible information in printed matter, has attracted attention for the purpose of strengthening security such as copyright protection and counterfeit prevention. Invisible printing does not degrade the appearance even if it overlaps with visible images, so it is possible to use embedded information while maintaining the quality of ordinary printed matter.It is expected to be applied in various fields such as security. .

For example, Patent Literature 1 discloses that an invisible image can be formed without impairing the image quality of a visible image by including a specific metal nanorod in a toner.

Japanese Unexamined Patent Application Publication No. 2007-219103 JP 2006-118036 A JP 2006-169544 A

Y. Yuhoka, J.; Phys. Chem. B, 101, 6661 (1997) N. R. Janahoka, J.; Phys. Chem. B, 105, 4065 (2001) Chem. Commun. (2003), pp. 2376-2377. Li. S et al., Nano Res. 4, 723-728 (2011)

As a result of examining the toner described in Patent Document 1, the inventors of the present invention have recognized that further improvement is necessary for the invisibility of images in the visible light region.

One aspect of the present disclosure is directed to providing a toner that can provide an image that can have excellent readability in the near-infrared region and excellent invisibility in the visible light region.

Another aspect of the present disclosure is directed to providing a method for manufacturing the toner according to the present disclosure.

Another aspect of the present disclosure is directed to providing a method of reading an image formed using the toner of the present disclosure.

According to one aspect of the present disclosure, a toner having toner particles, the toner containing gold nanorods,
The gold nanorods are
Gold nanorods A having a peak in the aspect ratio range of 6.0 to 13.0 in the aspect ratio distribution measurement, and gold having a peak in the aspect ratio range of 1.6 to 2.6 in the aspect ratio distribution measurement Provided is a toner characterized by containing nanorods B and having a peak in the range of 580 to 650 nm when the light absorption wavelength of the gold nanorods B is measured.

Also, according to another aspect of the present disclosure, a toner having toner particles comprising:
the toner contains gold nanorods and an additive,
When the aspect ratio distribution of the gold nanorods contained in the toner is measured, the aspect ratio has a peak in the range of 6.0 to 13.0,
Provided is a toner characterized by having a peak in the range of 580 to 650 nm when the light absorption wavelength of the additive is measured.

According to another aspect of the present disclosure, there is provided a method of manufacturing a toner having toner particles, comprising:
obtaining toner particles containing gold nanorods A and gold nanorods B;
When the aspect ratio distribution of the gold nanorods A is measured, the aspect ratio has a peak in the range of 6.0 to 13.0,
When the aspect ratio distribution of the gold nanorods B is measured, the aspect ratio has a peak in the range of 1.6 to 2.6,
A method for producing a toner is provided, wherein the gold nanorods B have a peak in the range of 580 to 650 nm when the light absorption wavelength is measured.

According to another aspect of the present disclosure, there is provided a method of manufacturing a toner having toner particles, comprising:
obtaining toner particles containing gold nanorods and additives;
When the aspect ratio distribution of the gold nanorods is measured, the aspect ratio has a peak in the range of 6.0 to 13.0,
There is provided a method for producing a toner, wherein the light absorption wavelength of the additive has a peak in the range of 580 to 650 nm.

Further, according to another aspect of the present disclosure, there is provided an image reading method comprising:
Provided is an image reading method comprising reading an image formed using the toner of the present disclosure using a device equipped with a near-infrared sensor.

According to one aspect of the present disclosure, it is possible to provide a toner capable of obtaining an image that can have excellent readability in the near-infrared region and excellent invisibility in the visible light region.

Further, according to another aspect of the present disclosure, it is possible to provide a method for manufacturing the toner according to the present disclosure.

Another aspect of the present disclosure can provide a method of reading an image formed using the toner of the present disclosure.

FIG. 4 is an explanatory diagram of an image reading method;

Unless otherwise specified, the descriptions of "○○ or more and XX or less" or "○○ to XX" that represent a numerical range mean a numerical range including the lower and upper limits that are endpoints. When numerical ranges are stated stepwise, the upper and lower limits of each numerical range can be combined arbitrarily.

The toner according to the present disclosure is preferably an invisible image forming toner.

<Circumstances leading to the invention>
When an image is formed using a toner containing gold nanorods, it is easy to obtain an image that can be read in the near-infrared region. As a result of further studies on this toner by the present inventors, it was found that when a toner containing gold nanorods with an aspect ratio distribution peak controlled to 6.0 to 13.0 is used, the amount of light absorption in the near-infrared region is It has been found that excellent image readability can be obtained because of the increase in the

On the other hand, the present inventors have found that when a fixed image formed using a toner containing gold nanorods whose aspect ratio is controlled as described above is visually observed, it may exhibit a faint color. has discovered. When the light absorption spectrum of the fixed image was measured, it was found that although the above image showed the maximum absorption in the near infrared region, there was also a small light absorption peak around 530 nm. The inventors thought that a fixed image having the following characteristics could be obtained in some cases. A toner used for forming an invisible image is naturally required to be capable of forming an image that is difficult to see. Therefore, the present inventors have recognized that it is necessary to improve the coloration due to the absorption of light around 530 nm as described above to make it difficult to see.

As a result of intensive studies by the present inventors, a toner containing a gold nanorod A whose aspect ratio distribution peak is controlled to 6.0 to 13.0 and a material B having a light absorption peak at 580 to 650 nm has been found. , was found to be effective in forming an image having the properties as described above. Inference mechanisms and their respective constituents are described in detail below.

<Assumed mechanism for manifesting the effects of the present disclosure>
Since gold nanorods A, which have a distribution peak in the range of aspect ratio 6.0 to 13.0, are contained in the toner, they absorb light in the near infrared region (1000 to 1600 nm). It becomes easy to obtain an image having excellent readability in .

In addition, the above gold nanorods A also partially absorb light around 530 nm, but by containing the material B having a light absorption peak at 580 to 650 nm, the light absorption characteristics in the visible light region are more flat. That is, it becomes easier to obtain an image that has lower saturation and is difficult to visually recognize.

In the present disclosure, as a specific example of the above material B,
(i) Gold nanorods B having a light absorption peak at 580 to 650 nm and a distribution peak with an aspect ratio of 1.6 to 2.6
(ii) Additive B having a light absorption peak at 580 to 650 nm
is mentioned.

<Gold nanorods>
The toner according to the present disclosure contains gold nanorods. A gold nanorod is treated as a nanorod having a gold content of 80% or more.

The arrangement of the gold element and the metal element other than gold in the gold nanorod may be in the form of an alloy compounded at the atomic level, or in the form of a core-shell structure in which the gold nanorod is coated with a metal element other than gold. . Also, the gold nanorods may be coated with a shell made of silica, polystyrene, or the like, for example. Furthermore, the surfaces of the gold nanorods may be modified with suitable molecules such as surfactants, depending on the purpose, such as dispersing the gold nanorods in the medium.

A gold nanorod refers to a gold nanomaterial having a major axis diameter and a minor axis diameter in a TEM image. That is, the gold nanorods in the TEM image are observed as substantially rectangular. Generally, the minor axis length is 1 nm to 60 nm and the major axis length is 20 nm to 500 nm. A value obtained by dividing the length of the long axis of the gold nanorod by the length of the short axis is called an aspect ratio. In the present disclosure, those with an aspect ratio of 1.5 or more are treated as gold nanorods.

<Gold nanorod A>
The toner contains gold nanorods, and the gold nanorods have gold nanorods A having a peak in the aspect ratio range of 6.0 to 13.0 in the measurement of the aspect ratio distribution.

Here, in the aspect ratio distribution, the peak wavelength at which the light absorption of the gold nanorods having the peak in the range of 6.0 to 13.0 is likely to exist in the range of 1000 to 1600 nm. It exhibits excellent absorption for wavelengths in the outer region. That is, when the light absorption wavelength of the gold nanorods A is measured, it preferably has a peak in the range of 1000 to 1600 nm. For this reason, the toner having the gold nanorods described above facilitates obtaining an invisible image that can have excellent readability in the near-infrared region.

The above aspect ratio is more preferably 9.0 or more, and preferably 11.0 or less.

In addition, the standard deviation of the aspect ratio distribution of the gold nanorods A contained in the toner is preferably 4.5 or less, more preferably 3.5 or less, and 2.0 or less. is more preferred. The lower limit is not particularly limited, and is preferably 0.5 or more.

<Content ratio of gold nanorods A>
The content of the gold nanorods A in the toner is preferably 0.001 to 0.200% by mass. If it is 0.001% by mass or more, an invisible image is likely to be visualized when irradiated with infrared rays, and an image having excellent readability is likely to be obtained. Therefore, it is preferably 0.001% by mass or more, more preferably 0.005% by mass or more. Further, when the content is 0.200% by mass or less, the volume resistivity of the toner is less likely to decrease, a high-quality invisible image is likely to be obtained, and readability in the near-infrared region is likely to be excellent. Therefore, it is preferably 0.200% by mass or less, more preferably 0.100% by mass or less, and even more preferably 0.050% by mass or less.

<Material B>
As described above, the present inventors have found that by including not only the gold nanorods A but also the material B, which has a light absorption peak at 580 to 650 nm, in the toner, an image that is difficult to see can be easily obtained. Specific examples of material B in the present disclosure include gold nanorods B and additive B below.

<Gold nanorod B>
The following gold nanorods B are listed as one of the embodiments of the material B described above. That is, the toner according to one aspect of the present disclosure contains gold nanorods B having a peak in the aspect ratio range of 1.6 to 2.6 in the aspect ratio distribution measurement, and the light absorption wavelength of the gold nanorods B is measured. , it has a peak in the range of 580 to 650 nm. The above aspect ratio range is preferably from 2.0 to 2.2.

Gold nanorods whose aspect ratio is controlled as described above tend to have a light absorption peak wavelength in the range of 580 to 650 nm. easy to get

The standard deviation of the aspect ratio distribution of the gold nanorods B contained in the toner is preferably 4.5 or less, more preferably 3.5 or less, and 2.0 or less. is more preferred. The lower limit is not particularly limited, and is preferably 0.5 or more.

From the viewpoint of invisibility in the visible light region and readability in the near-infrared region, the mass ratio of the gold nanorods A and gold nanorods B contained in the toner is (0.99/0.01) to (0.85/ 0.15).

<Additive B>
Another aspect of the material B is an additive (hereinafter also referred to as additive B) having a light absorption wavelength peak in the range of 580 to 650 nm. That is, the toner according to one aspect of the present disclosure contains an additive, and has a peak in the range of 580 to 650 nm when the light absorption wavelength of the additive is measured.

In addition, from the viewpoint of invisibility in the visible light region and readability in the near infrared region, the mass ratio of the gold nanorod A and the additive B is from (0.99/0.01) to (0.95/0 .05).

As the additive B having a light absorption peak wavelength in the range of 580 nm to 650 nm, a coloring agent for cyan toner or a coloring agent for magenta toner that satisfies the above conditions can be used. is more preferred.

Examples of cyan toner pigments include the following. C. I. Pigment Blue 2, 3, 15:2, 15:3, 15:4, 16, 17; C.I. I. Bat Blue 6; C.I. I. Acid Blue 45, a copper phthalocyanine pigment having a phthalocyanine skeleton substituted with 1 to 5 phthalimidomethyl groups.

As dyes for cyan toners, C.I. I. Solvent Blue 70 can be mentioned.

Examples of magenta toner pigments include the following. C. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48:2, 48:3, 48:4, 49, 50, 51, 52, 53, 54, 55, 57:1, 58, 60, 63, 64, 68, 81: 1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 146, 147, 150, 163, 184, 202, 206, 207, 209, 238, 269, 282; I. Pigment Violet 19; C.I. I. Bat Red 1, 2, 10, 13, 15, 23, 29, 35.

Dyes for magenta toner include the following. C. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121; C.I. I. disperse thread 9;C. I. Solvent Violet 8, 13, 14, 21, 27; C.I. I. Oil-soluble dyes such as Disper Violet 1, C.I. I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; C.I. I. Basic dyes such as Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

Further, a coloring agent for yellow toner may be contained for chromaticity adjustment.

Examples of yellow toner pigments include the following. C. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185; I. Bat Yellow 1, 3, 20.

As a yellow toner dye, C.I. I. Solvent Yellow 162 is mentioned.

A pigment may be used alone, but it is more preferable to use a dye and a pigment in combination to improve the clarity from the viewpoint of chromaticity adjustment.

<Gold nanoparticles>
It is preferable that the toner does not contain gold nanoparticles or contains gold nanoparticles at a rate of 30% by number or less with respect to the number of gold nanorods. In the present disclosure, gold nanoparticles are treated as metal nanoparticles containing gold as a main component. In addition, metal nanoparticles are treated as nanoparticles having an aspect ratio of less than 1.5. Gold nanoparticles may be produced during the preparation of gold nanorods. In addition, gold nanoparticles show absorption in the visible light region according to their particle size. For example, when the particle size is 20 nm, light absorption occurs around 520 nm. When the amount of gold nanoparticles in the toner is small, the light absorptance in the visible light region corresponding to the absorption wavelength of the gold nanoparticles is low, and an image with excellent invisibility can be easily obtained.

The number ratio of gold nanoparticles can be controlled by the reaction conditions and purification conditions described later.

<Method for preparing gold nanorods>
Examples of methods for preparing gold nanorods include electrolytic methods (Non-Patent Document 1) and chemical synthesis methods (Non-Patent Document 2).

For example, a method of synthesizing gold nanorod particles by reducing gold ions in an aqueous solution containing an excess amount of cetyltrimethylammonium bromide (CTAB), which is a quaternary ammonium salt, can be used. For details of the method, for example, Patent Document 2, Patent Document 3, Non-Patent Document 3, etc. can be referred to. In this method, first, a solution containing seed particles is prepared by adding an aqueous CTAB solution to an aqueous solution of chloroauric acid tetrahydrate and then adding sodium borohydride. To the solution, a mixed solution of silver nitrate, chloroauric acid tetrahydrate, L-ascorbic acid and CTAB is added and held for a certain period of time, or by adding the solution little by little, seed particles as nuclei can be grown anisotropically, and gold nanorods can be obtained.

Also, gold nanorods with a large aspect ratio can be obtained by adding benzyldimethylhexadecylammonium chloride when growing the seed particles. Gold nanorods with a large aspect ratio can also be obtained by performing reduction with sodium borohydride, which is a strong reducing agent, in the first step, followed by reduction with triethylamine, which is a weak reducing agent.

Also, if necessary, the gold nanorods can be refined to adjust the aspect ratio distribution and used. Any generally known method can be used for purification, and for example, density gradient ultracentrifugation can be used. For details of the method, for example, Non-Patent Document 4 can be referred to. Specifically, first, mixed solutions of sucrose and CTAB with different concentrations are prepared and layered in order of concentration gradient in a centrifugation tube. A sample of gold nanorods is layered on top of it and centrifuged to perform separation based on density and size. By separating and purifying in this way, the standard deviation σ is reduced, and gold nanorods with a narrower aspect ratio distribution can be obtained.

<Toner and Toner Particles>
The toner particles preferably contain a binder resin. The binder resin is not particularly limited, and specific examples include vinyl-based resins, polyester resins, epoxy resins, and the like, and these can be used alone or in combination. The binder resin may be a resin having a linear molecular structure, a branched resin, a crosslinked resin, or a mixture thereof.

<Light absorption rate in the near-infrared region>
Further, in a spectroscopic analysis of a fixed image formed with a toner lay-on amount of 0.30 mg/cm ² , it is preferable that the maximum value of light absorptance in the wavelength range of 900 nm or more and 1800 nm or less is 3% or more. This wavelength range corresponds to the near-infrared region, and if the light absorption rate is 3% or more, it is easy to read an invisible image using a near-infrared camera or the like. More preferably, it is 10% or more, and still more preferably 15% or more.

The above absorptivity can be controlled by adjusting the aspect ratio distribution of the gold nanorods.

<Weight Average Particle Diameter of Toner Particles (D4)>
The weight average particle size (D4) of the toner particles is preferably 4.0 μm or more and 9.0 μm or less, more preferably 5.0 μm or more and 7.0 μm or less. This range is advantageous for high-definition image formation.

<Toner manufacturing method>
The method for producing the toner is not particularly limited, but preferably includes a step of obtaining toner particles containing the gold nanorods A and the gold nanorods B as one aspect. Further, as another aspect, it is preferable to include a step of obtaining toner particles containing the gold nanorods A and the additive B.

Examples of the toner production method include the following toner production methods (1) to (3).

(1) Pulverization Method When producing a toner by the pulverization method, first, gold nanorods are thoroughly mixed with a binder resin as a dispersion medium and other additives using a mixer such as a Henschel mixer or a ball mill. The mixture is melt-kneaded using a kneader, extruder, or other thermal kneader using heat and mechanical shearing force to make the resins compatible with each other. After the melt-kneaded product is solidified by cooling, the solidified product is pulverized and the pulverized product is classified to obtain toner particles having a desired particle size.

(2) Polymerization method In the polymerization method, for example, gold nanorods, a polymerizable monomer capable of forming a binder resin, and, if necessary, a polymerization initiator, a cross-linking agent, a charge control agent, and other additives are uniformly added. Disperse to obtain a polymerizable monomer composition. Thereafter, the resulting polymerizable monomer composition is dispersed and granulated in a continuous layer (e.g., aqueous phase) containing a dispersion stabilizer using a suitable stirrer, and polymerized using a polymerization initiator. A reaction is carried out to obtain toner particles having the desired particle size.

(3) Emulsion Aggregation Method When producing a toner by the emulsion aggregation method, first, materials such as gold nanorods, a binder resin, and other additives are dispersed and mixed in an aqueous medium containing a dispersion stabilizer. A surfactant may be added to the aqueous medium. After that, by adding a flocculating agent, the toner particles are aggregated to a desired particle size, and then, or at the same time as the aggregation, the fine resin particles are fused. Further, if necessary, toner particles are formed by shape control by heat. After that, toner particles are obtained through a filtration washing process and a drying process.

Further, if necessary, a step of dispersing the gold nanorods in the binder resin may be provided in the series of toner manufacturing steps.

As a method for dispersing the gold nanorods in the binder resin, for example, a method using a masterbatch during the toner manufacturing process can be exemplified. That is, the gold nanorods are mixed with a part of the binder resin so as to have a high concentration, and melt-kneaded while applying a high shear to produce a masterbatch in which the gold nanorods are finely dispersed. After that, the masterbatch is melt-kneaded while being diluted with the remaining binder resin. A kneader, a Banbury mixer, a two-roll mill, a three-roll mill, etc. can be exemplified as a melt-kneading device suitably used when producing the masterbatch, and these can be used alone or in combination. A twin-screw kneader or the like can be exemplified as a melt kneading device used for dilution kneading.

Further, if necessary, a step of suppressing aggregation of the gold nanorod particles may be provided during a series of toner production steps.

As a method for suppressing aggregation of the gold nanorod particles during toner production, for example, a method of rapidly cooling after the melt-kneading step can be exemplified. For example, the melt-kneaded material can be rapidly cooled by spreading the melt-kneaded material on a water-cooled metal belt in the form of a sheet. Aggregation of gold nanorods that occurs during cooling can be suppressed by rapid cooling. Suitable cooling devices for rapid cooling include "NR double belt cooler for high viscosity (manufactured by Nippon Belting Co., Ltd.)", "cooling and solidifying machine belt drum flaker (manufactured by Nippon Coke Kogyo Co., Ltd.)", "cooling and solidifying Equipment drum flaker (manufactured by Katsuragi Industry Co., Ltd.)” and the like can be exemplified.

The step of dispersing the gold nanorod particles in the binder resin and the method of suppressing aggregation of the gold nanorod particles may be used in combination.

<Image reading method>
A method for reading an image formed using the toner according to the present disclosure is not particularly limited. Since an image formed using the toner according to the present disclosure tends to absorb wavelengths in the near-infrared region, an image reading method using light with a wavelength of 900 to 2500 nm is preferable. More preferably 900 to 1800 nm.

Further, since it is easy to read light of this wavelength, it is preferable to use an image reading method using a device equipped with a near-infrared sensor, and more preferably an image reading method using a device equipped with an InGaAs sensor. An InGaAs camera is more preferable.

As an example of the image reading method, the operations performed by the inventors are shown below.

After forming an evaluation image using the toner according to the present disclosure, the evaluation image 201 was observed by installing a light source 202 and a camera 203 as shown in FIG. That is, an evaluation image was placed on a desk, and infrared rays were irradiated using the light source 202 from a position about 1 m away from the evaluation image at an angle of 15°. Also, the camera 203 was installed 15 cm above the evaluation image and photographed. As the light source 202, a halogen lamp light source (trade name: PCS-UHX-150, manufactured by Nihon P.I. Co., Ltd.) equipped with a visible light cut filter unit was used. As the camera 203, a near-infrared camera (trade name: NVU3VD, manufactured by IR Spec Co., Ltd., InGaAs camera) having a lens portion equipped with a filter for cutting wavelength components of 800 nm or less was used. The near-infrared camera had a spectral sensitivity wavelength range of 970 to 1650 nm.

<Various additives>
If necessary, the toner may contain one or more additives selected from waxes, charge control agents, external additives, and the like.

<Wax>
Although the wax is not particularly limited, colorless or light-colored waxes are preferred, and examples thereof include the following.

Hydrocarbon waxes, ester waxes, amide waxes, higher fatty alcohols, higher fatty acids, etc. One type of wax may be used alone, or a plurality of types may be used in combination.

<Charge control agent>
Although the charge control agent is not particularly limited, a colorless or light-colored charge control agent is preferable, and examples thereof include the following.

Aromatic oxycarboxylic acids, metal compounds of aromatic oxycarboxylic acids, boron compounds, quaternary ammonium salts, calixarene, resins having sulfonic acid (salt) groups, resins having sulfonic acid ester groups, and the like. One type of charge control agent may be used alone, or a plurality of types may be used in combination.

<External Additives>
Although the external additive is not particularly limited, it is preferably colorless or light-colored, and examples thereof include the following.

Silica, alumina, titanium oxide, strontium titanate, silicon nitride, polytetrafluoroethylene, zinc stearate, etc. Moreover, the surface of the external additive may be hydrophobized.

Further, the average particle size of the primary particles of the external additive is preferably 1/10 or less of the weight average particle size (D4) of the toner particles.

<Developer>
The toner can be used as a one-component developer, but may be mixed with a carrier and used as a two-component developer. As the carrier, magnetic particles made of known materials such as metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. Also, a coated carrier in which the surface of the carrier is coated with a coating agent such as a resin, or a resin-dispersed carrier in which magnetic particles are dispersed in a binder resin may be used. The volume average particle size of the carrier is preferably 15 μm or more and 100 μm or less, more preferably 25 μm or more and 80 μm or less.

<Various measurement methods, etc.>
Various measurement methods and the like are described below.

<Method for Measuring Weight Average Particle Diameter (D4) of Toner Particles>
The weight average particle diameter (D4) of toner particles is calculated as follows.

As a measuring device, a precision particle size distribution measuring device "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.) using a pore electrical resistance method equipped with a 100 μm aperture tube is used. The attached dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.) is used for setting the measurement conditions and analyzing the measurement data. The measurement is performed with 25,000 effective measurement channels.

The electrolytic aqueous solution used for the measurement can be prepared by dissolving special-grade sodium chloride in ion-exchanged water to a concentration of about 1% by mass, such as "ISOTON II" (manufactured by Beckman Coulter, Inc.). .

Before performing measurement and analysis, set the dedicated software as follows.

On the "Change standard measurement method (SOM)" screen of the above dedicated software, set the total count number in control mode to 50,000 particles, set the number of measurements to 1, and set the Kd value to "standard particle 10.0 μm" (Beckman・Set the value obtained using Coulter Coulter). By pressing the "threshold/noise level measurement button", the threshold and noise level are automatically set. Also, set the current to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and put a check in the “Flush aperture tube after measurement” box. On the "pulse-to-particle size conversion setting" screen of the dedicated software, set the bin interval to logarithmic particle size, the particle size bin to 256 particle size bins, and the particle size range from 2 μm to 60 μm.

A specific measuring method is as follows.

(1) About 200 mL of the electrolytic aqueous solution is placed in a 250 mL round-bottomed glass beaker exclusively for Multisizer 3, set on a sample stand, and stirred with a stirrer rod counterclockwise at 24 revolutions/second. Then, remove dirt and air bubbles inside the aperture tube using the dedicated software's "Flush Aperture" function.

(2) Put about 30 mL of the electrolytic aqueous solution into a 100 mL flat-bottom glass beaker. As a dispersant, "Contaminon N" (a 10% by mass aqueous solution of a neutral detergent for cleaning precision measuring instruments at pH 7 consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, made by Fujifilm Wako Pure Chemical Industries, Ltd. ) is diluted with ion-exchanged water to about 3 times the mass, and about 0.3 mL of the solution is added.

(3) Prepare an ultrasonic disperser "Ultrasonic Dispersion System Tetora 150" (manufactured by Nikkaki Bios Co., Ltd.) having an electric output of 120 W and incorporating two oscillators with an oscillation frequency of 50 kHz with a phase shift of 180 degrees. About 3.3 liters of deionized water is placed in the water tank of the ultrasonic disperser, and about 2 mL of Contaminon N is added to this water tank.

(4) The beaker of (2) above is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. Then, the height position of the beaker is adjusted so that the resonance state of the liquid level of the electrolytic aqueous solution in the beaker is maximized.

(5) While the electrolytic aqueous solution in the beaker of (4) above is being irradiated with ultrasonic waves, about 10 mg of toner particles are added little by little to the electrolytic aqueous solution and dispersed. Then, the ultrasonic dispersion treatment is continued for another 60 seconds. In the ultrasonic dispersion, the temperature of the water in the water tank is appropriately adjusted to 10°C or higher and 40°C or lower.

(6) Into the round-bottomed beaker of (1) set up in the sample stand, the electrolytic aqueous solution of (5) above in which toner particles are dispersed is dropped using a pipette, and the measured concentration is adjusted to about 5%. do. The measurement is continued until the number of measured particles reaches 50,000.

(7) Analyze the measurement data using the dedicated software attached to the apparatus, and calculate the weight average particle size (D4). The "average diameter" on the "analysis/volume statistical value (arithmetic mean)" screen when graph/vol% is set in the dedicated software is the weight average particle diameter (D4).

<Measurement method of peak aspect ratio and standard deviation in aspect ratio distribution of gold nanorods>
A measurement sample in which gold nanorods are dispersed in a solvent is dropped onto the support film, dried, and then subjected to TEM observation using a transmission electron microscope “Technai F30 (manufactured by FEI)” or the like. The peak aspect ratio and standard deviation in the aspect ratio distribution can be determined by determining the lengths of the major and minor axes of the observed gold nanorods using image processing software such as Photoshop.

When measuring the aspect ratio distribution of the gold nanorods contained in the toner, the above measurement is performed after the gold nanorods contained in the toner are separated and collected.

The procedure first dissolves the toner using a solvent capable of dissolving the binder resin. Next, the gold nanorods are sedimented by centrifugation, and the supernatant is separated. A new solvent is added, centrifugation is performed again, and the supernatant is separated. By repeating this operation several times for washing and finally removing the solvent by drying, the gold nanorods can be separated and recovered from the toner. It can also be weighed before being redispersed in the solvent.

EXAMPLES The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited by these examples.

<Production Example of Dispersion A Containing Gold Nanorods A According to the Present Disclosure>
[Preparation of seed particle solution]
500 mL of a 0.0005 mol/L chloroauric acid tetrahydrate (Kishida Chemical Co., Ltd.) aqueous solution and 500 mL of a 0.2 mol/L cetyltrimethylammonium bromide (Kishida Chemical Co., Ltd.) aqueous solution were mixed. A seed particle solution (solution A) was obtained by adding 60 mL of 0.01 mol/L sodium borohydride (Tokyo Chemical Industry Co., Ltd.) to this aqueous solution.

[Step a]
10 g of cetyltrimethylammonium bromide was dissolved in 500 mL of an aqueous solution of 0.15 mol/L benzyldimethylhexadecylammonium chloride (Tokyo Chemical Industry Co., Ltd.). 20 mL of a 0.004 mol/L silver nitrate aqueous solution was added to the aqueous solution containing the two kinds of surfactants. After adding 500 mL of 0.001 mol/L chloroauric acid tetrahydrate aqueous solution to this aqueous solution, 7 mL of 0.078 mol/L L-ascorbic acid aqueous solution (Kishida Chemical Co., Ltd.) was further added. This solution was designated as Solution B.

Subsequently, 10 g of cetyltrimethylammonium bromide was dissolved in 500 mL of a 0.15 mol/L aqueous solution of benzyldimethylhexadecylammonium chloride (Tokyo Chemical Industry Co., Ltd.). 20 mL of a 0.004 mol/L silver nitrate aqueous solution was added to the aqueous solution containing the two kinds of surfactants. After adding 500 mL of 0.0005 mol/L chloroauric acid tetrahydrate aqueous solution to this aqueous solution, 3.6 mL of 0.078 mol/L L-ascorbic acid aqueous solution (Kishida Chemical Co., Ltd.) was further added. This solution was designated as Solution C.

1.2 mL of solution A was added dropwise to solution B, and then 2.0 mL of solution C was added at a rate of 1.0 mL/20 minutes to anisotropically grow seed particles as nuclei. After centrifugation at 10,000×g for 5 minutes, 99.98 parts by mass of THF and 0.02 parts by mass of gold nanorods were redispersed in THF to obtain a particle dispersion.

[Purification process]
6 mL of the resulting particle dispersion was centrifuged at 10,000×g for 5 minutes and the resulting pellet was resuspended in 0.05 mL of 0.01 M CTAB aqueous solution.

Further, solutions were prepared by adding sucrose to 0.01 M CTAB solution at concentrations of 10% by weight, 15% by weight, 20% by weight, and 25% by weight. These liquids were placed in a 15 mL polyallomer tube in 3 mL portions in descending order of sucrose concentration, and finally the resuspended particle dispersion was overlaid. Centrifugation was performed at 25° C. and 10,750×g for 15 minutes using a high-speed refrigerated centrifuge Avanti JXN-30. After centrifugation, the mixture was divided into 300 μL fractions. TEM images of the gold nanorods in each fraction were measured. After confirming the aspect ratio and standard deviation calculated from the TEM image of each fraction, the desired fractions were collected and the combined solution was centrifuged at 10,000×g for 5 minutes. The precipitated gold nanorods were re-dispersed in a dispersion medium (THF) so as to be 0.02 parts by mass, and the final concentration was 99.98 parts by mass of THF and 0.02 parts by mass of gold nanorods. Dispersion A was thus prepared. Table 1 shows the physical properties of the gold nanorods contained in the dispersion A.

<Production Examples of Dispersions B to F Containing Gold Nanorods A According to the Present Disclosure>
Production of dispersion liquid A except that the peak aspect ratio and standard deviation were changed as shown in Table 1 by adjusting the amount of solution C in step a, the presence or absence of the purification step, and which fraction was collected in the purification step. Dispersions B to F were obtained in the same manner as in Examples. Table 1 shows the physical properties of the gold nanorods contained in the dispersion.

However, in Dispersion D, styrene was used as the final dispersion medium instead of THF, and the final concentration was 99.9 parts by mass of styrene and 0.1 part by mass of gold nanorods.

<Production Example of Dispersion G Containing Gold Nanorods B According to the Present Disclosure>
[Preparation of seed particle solution]
First, a seed particle solution (solution A) similar to that described above was prepared.

[Step b]
3.8 mL of 0.004 mol/L silver nitrate (Kishida Chemical Co., Ltd.) aqueous solution was added to 500 mL of 0.2 mol/L cetyltrimethylammonium bromide aqueous solution. After adding 500 mL of 0.001 mol/L chloroauric acid tetrahydrate aqueous solution to this aqueous solution, 7 mL of 0.078 mol/L L-ascorbic acid aqueous solution (Kishida Chemical Co., Ltd.) was further added. This solution was designated as Solution B.

Then, 1.2 mL of Solution A was added dropwise to Solution B. This solution was held at 30° C. for 20 minutes to anisotropically grow seed particles as nuclei to obtain a particle dispersion.

[Purification process]
Dispersion G was prepared by performing the same operation as the purification step in Production Example of Dispersion A using the particle dispersion obtained in Step b. Table 1 shows the physical properties of the gold nanorods contained in the dispersion G.

<Production Examples of Dispersions H to O Containing Gold Nanorods B According to the Present Disclosure>
Same as Production Example of Dispersion G, except that the peak aspect ratio and standard deviation were changed as shown in Table 1 by adjusting the amount of silver nitrate aqueous solution added in step b and which fraction was collected in the purification step. were carried out to obtain Dispersions H to O. Table 1 shows the physical properties of the gold nanorods contained in each dispersion.

However, in dispersion O, styrene was used as the final dispersion medium instead of THF, and the final concentration was 99.9 parts by mass of styrene and 0.1 part by mass of gold nanorods.

<Production Example of Dispersion P Containing Additive B According to the Present Disclosure>
・Pigment (C.I. Pigment Blue 15:3) 1000 parts by mass ・Anionic surfactant 150 parts by mass ・Ion-exchanged water 9000 parts by mass After mixing and dissolving the above materials, disperse using a high-pressure impact disperser. Dispersion liquid P was obtained. Table 1 shows the physical properties of the pigment contained in the dispersion.

<Production Examples of Comparative Dispersions Q to T>
Same as Production Example of Dispersion G, except that the peak aspect ratio and standard deviation were changed as shown in Table 1 by adjusting the amount of silver nitrate aqueous solution added in step b and which fraction was collected in the purification step. were performed to obtain dispersions Q to T. Table 1 shows the physical properties of the gold nanorods contained in each dispersion.

The peak aspect ratio and standard deviation in the aspect ratio distribution in Table 1 were measured by the above-described measurement method.

In addition, those with a light absorption peak wavelength in the range of 400 to 800 nm were measured using an ultraviolet-visible-near-infrared spectrophotometer (trade name: UV-3600, manufactured by Shimadzu Corporation). In addition, those with a light absorption peak wavelength in the range of 900 to 1800 nm were measured using an ultraviolet-visible-near-infrared spectrophotometer (trade name: MV-3300, manufactured by JASCO Corporation).

<Example 1>
<Production example of toner 1 (melt-kneading method)>
[Production Example of Saturated Polyester 1 Dispersion]
・ Saturated polyester 1 (polycondensation product of ethylene oxide-modified bisphenol A and terephthalic acid, glass transition temperature 60 ° C., weight average molecular weight 29000, number average molecular weight 6000) 20.0 parts by mass THF 80.0 parts by mass Mix well to obtain a saturated polyester 1 dispersion.

[Production Example of Toner Particle 1]
・Dispersion I 2.0 parts by mass ・Dispersion B 31.0 parts by mass ・Saturated polyester 1 dispersion 67.0 parts by mass It was made to reprecipitate by dripping. A mixture of gold nanorods and saturated polyester was obtained in a powder state by collecting the precipitates by suction filtration. 5.0 parts by mass of ester wax (melting point 73° C.) was added to 100 parts by mass of this mixture, and the above materials were sufficiently mixed using an FM mixer (manufactured by Nippon Coke Kogyo Co., Ltd.). Melt-kneading was carried out using Model -30 (manufactured by Ikegai Co., Ltd.) to obtain a kneaded product. The resulting kneaded product was spread on a water-cooled metal belt in the form of a sheet, rapidly cooled, and then coarsely pulverized to 1 mm or less by a hammer mill to obtain a coarsely pulverized product. The coarsely ground material obtained was pulverized with T-250 (manufactured by Freund Turbo Co.). Further, classification was performed using 200TSP (manufactured by Hosokawa Micron Corporation) to obtain toner particles 1 having a weight average particle diameter (D4) of 5.9 μm.

[External addition process]
100.0 parts by mass of the obtained toner particles 1 and 1.0 parts by mass of hydrophobic silica fine powder (number average particle size of primary particles: 7 nm) surface-treated with hexamethyldisilazane were mixed in an FM mixer (Nippon Coke (manufactured by Kogyo Co., Ltd.) to obtain Toner 1.

[evaluation]
Next, using Toner 1 obtained, the following evaluations were performed.

<Evaluation of invisibility in the visible light region>
<Method for measuring light absorptance in the wavelength range of 400 nm or more and 800 nm or less>
As an image forming apparatus, a color printer (trade name: LBP652C, manufactured by Canon Inc.) modified so that the development contrast can be freely changed was used, and the toner in the black developing device was replaced with toner 1. A4 paper (trade name: GF-C081, Canon Marketing Japan Inc.) was used as the paper, and the amount of toner 1 applied was 0.30 mg/cm ² under the environment of 25°C temperature and 60% relative humidity. A sample image was obtained by forming a rectangular image of 1 cm x 10 cm as described above.

The image output above was visually confirmed and the invisibility was evaluated.

Evaluation criteria are as follows.
A: Difficult to distinguish rectangular images B: Somewhat difficult to distinguish rectangular images C: Neither easy nor difficult to distinguish rectangular images D: Somewhat easy to distinguish rectangular images E: Easy to distinguish rectangular images Evaluation above Those that were A or B in the criteria were judged to have excellent invisibility.

<Evaluation of readability in the near-infrared region>
<Method for measuring light absorptance in the wavelength range of 900 nm or more and 1800 nm or less>
For the sample image used in the above invisibility evaluation, an ultraviolet-visible near-infrared spectrophotometer (trade name: MV-3300, manufactured by JASCO Corporation) was used to spectroscopically measure the wavelength range of 900 nm or more and 1800 nm or less. did The maximum absorbance obtained from the measurement was taken as the measured value of the sample image. A sheet of paper itself was also measured as a blank, and the infrared absorption rate (%) was obtained by subtracting the measured value of the blank from the measured value of the sample image. Table 3 shows the results. It was judged that the effect of the present disclosure was obtained when the infrared absorption rate (%) was 3% or more. When an image with an infrared absorption rate of 3% was confirmed using a near-infrared camera (trade name: NVU3VD, manufactured by IR Spec), it was found that it could be read as an invisible image. On the other hand, when an image with an infrared absorptivity of 2% was confirmed using the above-described near-infrared camera, it was determined that the image exceeded the degree that could be read as an invisible image.

<Examples 2 to 10, 12 to 14>
Toners 2 to 10 and 12 to 14 were produced and evaluated in the same manner as in Example 1 except that the type and amount of the dispersion liquid were changed as shown in Table 2. Table 3 shows the evaluation results.

<Example 11>
<Production Example of Toner 11 (Polymerization Method)>
[Step of preparing aqueous medium]
1000.0 parts by mass of ion-exchanged water and 14.0 parts by mass of sodium phosphate 12-hydrate were charged into a reaction vessel and kept at 65° C. for 1 hour while purging with nitrogen.

The mixture was stirred at 12,000 rpm using a high-speed stirrer "TK Homomixer" (manufactured by Primix). A calcium chloride aqueous solution prepared by dissolving 9.2 parts by mass of calcium chloride dihydrate in 20.0 parts by mass of ion-exchanged water was added all at once to prepare an aqueous medium containing a fine dispersion stabilizer.

[Preparation step of polymerizable monomer composition]
A mixture was obtained by mixing the following materials.
・Dispersion O 2.8 parts by mass ・Dispersion D 42.0 parts by mass ・Styrene 128.9 parts by mass ・n-Butyl acrylate 34.0 parts by mass ・Aluminum salicylate compound (Bontron E-88 manufactured by Orient Chemical Industry Co., Ltd.) 1.0 parts by mass Saturated polyester 2 (polycondensate of propylene oxide-modified bisphenol A and isophthalic acid, glass transition temperature 65°C, weight average molecular weight 10000, number average molecular weight 6000) 5.0 parts by mass Ester wax (DSC Peak temperature of maximum endothermic peak in measurement = 70°C, Mn = 704) 10.0 parts by mass Divinylbenzene 0.1 part by mass K. A homomixer was used to uniformly dissolve and disperse at 500 rpm to prepare a polymerizable monomer composition.

[Granulation process]
The temperature of the aqueous medium containing the above dispersion stabilizer was set at 70°C, and T.I. K. While maintaining the rotation speed of the homomixer at 12000 rpm, the above polymerizable monomer composition was put into the aqueous medium, and 10.0 parts by mass of t-butyl peroxypivalate as a polymerization initiator was added. After that, granulation was performed for 10 minutes while maintaining the number of revolutions at 12000 rpm.

[Polymerization step]
After the granulation step, the stirrer was changed to a propeller stirring blade, and the mixture was stirred at 150 rpm while maintaining the temperature at 70° C. for 5 hours to carry out polymerization.

[Washing and drying process]
After completion of the polymerization step, the liquid temperature was cooled to room temperature, diluted hydrochloric acid was added to adjust the pH to 1.5, and the mixture was stirred for 3 hours. Thereafter, filtration and washing were repeated to obtain a toner cake.

After pulverizing the obtained toner cake, it is dried with a flash dryer, and fine and coarse powder is cut with a multi-division classifier utilizing the Coanda effect, and the weight average particle diameter (D4) is 6.0. Toner particles 11 of 3 μm were obtained.

[External addition process]
100.0 parts by mass of the obtained toner particles 11 and 1.0 parts by mass of hydrophobic silica fine powder (number average particle size of primary particles: 7 nm) surface-treated with hexamethyldisilazane were mixed in a high-speed mixer "FM Mixer" (manufactured by Nippon Coke Kogyo Co., Ltd.) was used to obtain Toner 11.

[evaluation]
Using the obtained toner 11, the same evaluation as in Example 1 was performed. Table 3 shows the evaluation results.

<Comparative Examples 1 to 4>
Toners 15 to 18 were produced and evaluated in the same manner as in Example 1 except that the type and amount of the dispersion liquid were changed as shown in Table 2. Table 3 shows the evaluation results.

Claims (13)

A toner having toner particles, the toner containing gold nanorods,
The gold nanorods are
Gold nanorods A having a peak in the aspect ratio range of 6.0 to 13.0 in the aspect ratio distribution measurement, and gold having a peak in the aspect ratio range of 1.6 to 2.6 in the aspect ratio distribution measurement A toner containing nanorods B, wherein the light absorption wavelength of the gold nanorods B has a peak in the range of 580 to 650 nm. 2. The toner according to claim 1, wherein the gold nanorods A have a peak in the range of 1000 to 1600 nm when the light absorption wavelength of the gold nanorods A is measured. 3. The toner according to claim 1, wherein the gold nanorods B are gold nanorods having a peak in an aspect ratio range of 2.0 to 2.2 in the measurement of aspect ratio distribution. 4. The mass ratio of said gold nanorods A and said gold nanorods B contained in said toner is from (0.99/0.01) to (0.85/0.15). 1. The toner according to claim 1. The toner according to any one of claims 1 to 4, wherein the content of the gold nanorods A in the toner is 0.001 to 0.200% by mass. A toner having toner particles,
the toner contains gold nanorods and an additive,
When the aspect ratio distribution of the gold nanorods contained in the toner is measured, the aspect ratio has a peak in the range of 6.0 to 13.0,
A toner characterized by having a peak in the range of 580 to 650 nm when the light absorption wavelength of the additive is measured. 7. The toner according to claim 6, wherein the mass ratio of said gold nanorods and said additive contained in said toner is from (0.99/0.01) to (0.95/0.05). 8. The toner according to claim 6, wherein the content of the gold nanorods in the toner is 0.001 to 0.200 mass %. The toner according to any one of claims 1 to 8, which is a toner for forming an invisible image. Spectroscopic analysis of a fixed image formed using the toner with a toner loading of 0.30 mg/cm ² , wherein the maximum value of light absorptance in a wavelength range of 900 nm or more and 1800 nm or less is 3% or more. 10. The toner according to any one of 1 to 9. An image reading method comprising:
An image reading method, comprising the step of reading an image formed using the toner according to any one of claims 1 to 10, using a device equipped with a near-infrared sensor. A method for producing a toner having toner particles, comprising:
obtaining toner particles containing gold nanorods A and gold nanorods B;
When the aspect ratio distribution of the gold nanorods A is measured, the aspect ratio has a peak in the range of 6.0 to 13.0,
When the aspect ratio distribution of the gold nanorods B is measured, the aspect ratio has a peak in the range of 1.6 to 2.6,
A method for producing a toner, wherein the gold nanorods B have a peak in the range of 580 to 650 nm when the light absorption wavelength is measured. A method for producing a toner having toner particles, comprising:
obtaining toner particles containing gold nanorods and additives;
When the aspect ratio distribution of the gold nanorods is measured, the aspect ratio has a peak in the range of 6.0 to 13.0,
A method for producing a toner, wherein the additive has a peak in the range of 580 to 650 nm when measured for light absorption wavelength.

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