JP6593668B2 - Fine particle dispersibility evaluation equipment - Google Patents

Description

The present invention relates to a fine particle dispersion evaluation equipment in a solution containing fine particles composed of aggregated fine primary particles or primary particles are aggregated.

  Printing by an ink jet printer recording apparatus that is widely used at present is a system in which ink is ejected from nozzles and adhered to a recording material as a medium. Since this printing method is a printing method that does not use a plate unlike a conventional printing method such as gravure printing, a wide range of fields of use is expected as an on-demand printing method that can cope with a small variety of products. In particular, in recent years, many studies have been made on printing using a non-absorbing substrate such as plastic from printing using a conventional absorbing substrate such as paper as a recording material.

  In printing using plastic as a recording material, white ink is often used for the purpose of improving visibility. For example, transparent plastic films are used for packaging materials used for food and beverage packaging, etc. so that the contents can be confirmed, and white ink is used for the purpose of concealing the base to improve the color of printed matter. in use. As such a printing ink for a plastic film, an inorganic pigment having high concealability as a pigment, for example, fine particles made of titanium oxide which is a metal oxide is often used.

  Conventionally, as a general method for evaluating the dispersion state of the fine particles contained in the solution, a method of measuring the particle size distribution of the fine particles in the solution and showing dispersibility by the particle size is used. The fact that the degree of dispersion is small means that the particle size distribution of the fine particles is narrow and the size of the particles is more uniform. Methods for measuring the particle size include known and commonly used centrifugal sedimentation methods, laser diffraction / scattering methods, dynamic light scattering methods, electroacoustic effect (ESA) methods, capillary methods, scanning electron microscopes (SEM), and other electron microscope methods. Etc. are used. Particularly versatile is measurement by a laser particle size distribution meter (Microtrac UPA) using a dynamic light scattering method.

  On the other hand, in recent years, as a method for evaluating the dispersion state of filler fine particles contained in a light-transmitting solid sample such as a resin film, a method using a confocal laser microscope apparatus has attracted attention (for example, see Patent Document 1). . The confocal laser microscope apparatus is a method that enables simple and quick structural analysis in the submicron unit in the depth direction of a sample in a device state that does not require multi-section fabrication.

  As a method for evaluating the dispersion state of the fine particles in the solution, the method using an electron microscope such as the scanning electron microscope (SEM) described above can know only one cross-section information observed. Therefore, in the case of a solution in which fine particles are dispersed non-uniformly, there is a problem that a large number of observation points must be secured by multiplying time and man-hours. The conventional method for measuring the particle size distribution also has a problem that only a local dispersion state can be grasped. In addition, when measuring with a laser particle size distribution meter using the dynamic light scattering method, it is necessary to measure a solution in which fine particles are dispersed in a sufficiently diluted state with distilled water or the like, and measure the solution in a high concentration state. I have problems such as being unable to do so.

  Furthermore, when an inorganic pigment having a high specific gravity such as titanium oxide is dispersed in a solution such as an inkjet recording ink having a low viscosity, suppression of sedimentation becomes a problem. Depending on the dispersion state of the fine particles, the color development characteristic (hiding property) of the ink changes remarkably, so that it is necessary to accurately evaluate the state of the added and dispersed fine particles in submicron units. As a general method for evaluating the sedimentation property of fine particles, a visual evaluation method for putting a solution containing fine particles into a glass bottle and visually evaluating the sedimentation state at the bottom after a predetermined time has been implemented. It is hard to be accurate. Although there is a method for improving the dispersibility of the fine particles themselves made of titanium oxide, it is not versatile.

  Therefore, the present inventor has found that by using the confocal laser microscope device, the evaluation of the dispersibility and sedimentation of fine particles in a solution can be easily and quickly performed in a high concentration solution state. .

  In the confocal laser microscope apparatus, laser light, which is monochromatic light, is applied to a solution in which fine particles are dispersed. At this time, the bottom surface of the solution container containing the solution in which the fine particles are dispersed or a minute region in the solution is used as a focal plane of the microscopic optical system. If there are fine particles in the solution that have a particle size that interacts with the incident light wavelength (particle size approximately 1/10 or less of the wavelength), the incident light is scattered before and after the particle according to the Rayleigh scattering mechanism. Weak so-called backscattered light having the same wavelength as the light can be observed. Note that light having the same wavelength as the incident light observed when the laser beam is irradiated is called Rayleigh light.

  When the Rayleigh light as the backscattered light is extracted, and its intensity is detected and analyzed, information on the dispersion state of the fine particles in a minute region in the solution can be acquired. Backscattering three-dimensionally by shaking the X and Y scanners in the X-axis and Y-axis directions while moving the laser focal plane in the submicron order from the bottom of the solution container in the solution depth direction (Z direction). Rayleigh light that becomes light can be analyzed. By obtaining the depth position information of the dispersed state of the fine particles, it is considered that the dispersed state in the XY and Z directions of the fine particles in the depth direction in the solution can be evaluated in submicron units.

  Here, as described above, a general confocal laser microscope apparatus includes a scanning mechanism that scans in the XYZ direction including the depth direction, and scans the solution sample in the depth direction and the planar direction. However, by obtaining the above information, the solution sample can be evaluated three-dimensionally.

  However, when the concentration of fine particles in the solution is high, light attenuation due to absorption in fine particles (pigments) and solutions (conforms to Lambert-Beer law) and scattering in fine particles (scattering is also considered together with absorption in a broad sense). The measurement light is exponentially weakened in the depth direction. Therefore, until now, it has been the theory to evaluate the dispersibility by diluting the solution. In addition, fine particles made of an inorganic pigment such as a metal oxide having a large specific gravity immediately start to settle in the solution. For this reason, it is difficult to accurately evaluate dispersibility and sedimentation in an apparatus that takes time to measure one frame region (XY image) and an apparatus that takes time to set a solution sample.

The present invention has been made in view of the above problems. The purpose is to obtain accurate dispersion and sedimentation in a three-dimensional sub-micron unit easily and rapidly even in the case of fine particles having a large specific gravity and high sedimentation in a solution. to provide a fine particle dispersion evaluation equipment that can.

In order to solve the above problems, the invention of claim 1 is characterized in that a gripping member for gripping a solution container containing a solution sample in which fine particles are dispersed in a solution, a laser light source, and irradiating the solution sample with laser light. , A separation optical element that receives Rayleigh light including weak fine particle scattered light from the solution sample, a water immersion objective lens, and a confocal microscopic optical system including a pinhole conjugate with a focal plane, and the separation optical A filter optical element that transmits Rayleigh light in the light that has passed through the element, a spectroscopic means that splits light transmitted through the filter optical element, a light detection means that detects the intensity of light dispersed by the spectroscopic means, and A fine particle dispersion comprising a scanning mechanism capable of scanning laser light relative to the solution sample in the depth direction and the plane direction of the solution sample, and evaluating the dispersibility of the fine particles in the solution sample In the evaluation apparatus, a two-dimensional image data relating to the depth direction and the plane direction is constructed based on the shaking mechanism for shaking the solution container held by the holding member, and the intensity of the light detected by the light detection unit, An image processing unit that performs image processing for quantitative evaluation of fine particle dispersibility from the data , and irradiates the solution sample with linearly polarized laser light .

  According to the present invention, even in the case of fine particles having a large specific gravity and high sedimentation in a solution, an accurate dispersion state and sedimentation property can be obtained easily and rapidly in a three-dimensional submicron unit in a highly concentrated solution state. There is an excellent effect of being able to.

The block diagram which shows the structure of the fine particle dispersibility evaluation apparatus which concerns on this embodiment. Sectional drawing which shows the structure of the solution container used for the fine particle dispersibility evaluation apparatus. The block diagram which shows the principal part structure of the fine particle dispersibility evaluation apparatus. The flowchart which shows an example of the quantification method of the image process part of the same fine particle dispersibility evaluation apparatus. FIG. 4 is a diagram showing an example of a fine particle scattering image (XY cross section) acquired in Example 1. The figure which shows an example which specified arbitrary pixel areas among the fine particle scattering images acquired in FIG. It is an example of the histogram produced for the quantitative evaluation of a dispersion state by the image processing part, (a) shows a state with good dispersibility and (b) shows a state with poor dispersibility. FIG. 6 is a diagram showing an example of a fine particle scattering image (XY cross section) acquired in Example 2. The figure which shows an example of the fine particle scattering image (XY cross section) acquired in the comparative example 1. FIG.

Hereinafter, a fine particle dispersibility evaluation apparatus and a fine particle dispersibility evaluation method of the present invention will be described in detail with reference to the drawings.
First, the evaluation object in the present invention is not particularly limited, and examples thereof include a solution sample such as a white ink for aqueous inkjet recording in which an inorganic white pigment is dispersed as fine particles. Generally, a white ink contains an inorganic white pigment, a pigment dispersant, a binder, and water as a dispersant.

  Examples of the inorganic white pigment include silicas such as alkaline earth metal sulfates, carbonates, finely divided silicic acid, and synthetic silicates, calcium silicate, alumina, alumina hydrate, titanium oxide, zinc oxide, Examples include talc and clay. The inorganic white pigment may be surface-treated by various surface treatment methods.

  Among these, surface-treated titanium oxide is preferable because it exhibits relatively good dispersibility in an aqueous medium. For example, in order to avoid the influence of photocatalytic properties, titanium oxide surface-treated with an inorganic substance is preferable, and titanium oxide surface-treated with silica and alumina is more preferable. Furthermore, it is still possible to use titanium oxide that has been surface-treated with the silica and alumina and then surface-treated with a silane coupling agent. As the titanium oxide surface-treated with silica and alumina, known rutile type / anatase type titanium dioxide can be used, and rutile type titanium dioxide is more preferable.

  Moreover, as an average particle diameter of the said titanium oxide, it is preferable to use a 100-500 nm thing, and it is more preferable to use a 150-400 nm thing. When the average particle size is 100 nm or less, non-sedimentation and dispersion stability in an aqueous medium are more easily realized, but the whiteness and hiding properties are inferior, and the practicality as an original white ink may be reduced. is there. On the other hand, when the average particle size is 500 nm or more, there is no problem in terms of whiteness and concealment, but the discharge stability tends to be insufficient. A practically preferable particle diameter is 200 to 300 nm. In addition, the average particle diameter of the titanium oxide as a raw material uses what measured the particle size of 20 pieces with the electron micrograph, and took the average.

  The binder for white ink to be used can be used without any problem as long as it is a resin that can be mixed with water and exist in a uniform state. For example, it is preferable to use a water-based urethane resin or an olefin resin from the viewpoint of adhesion to a plastic film and adhesiveness.

  Specifically, a water-soluble or water-dispersible water-based urethane resin can be used as the water-based urethane resin used as a binder in the solution. The aqueous urethane resin used in the present embodiment is preferably an aqueous polyurethane resin, an aqueous urethane resin, or a solid content with respect to the total amount of the aqueous urethane resin ink, preferably 1 to 20 mass%, particularly preferably 2 to 10 mass%. .

  The olefin resin used as a binder in the solution can be used without particular limitation as long as it is an olefin resin that can be mixed with water and exist in a uniform state. A resin that can exist in a uniform state when mixed with water is dispersed in the form of fine particles in water (this includes a state in which dispersed particles are extremely small and dispersed in a single molecule), so-called water dispersibility. These resins may be used, and so-called water-soluble and water-soluble resins are also included. Specifically, for example, an olefin resin or a rubber-like material made of a copolymer or a homopolymer of olefin monomers such as ethylene, propylene, isobutylene, 1-butene, 1-pentene, 1-hexene and the like is used as a surfactant. And water-dispersible resins composed of a polyolefin component and a hydrophilic component such as an acid. The content of the solid content of the olefin resin used as the binder with respect to the total amount of the ink is generally used in the range of 0.5% by mass to 30% by mass. Among these, 1% by mass to 10% by mass is preferable.

  The water used in the solution may be water alone or a mixed solvent composed of a water-soluble organic solvent having compatibility between water and water. Examples of the water-soluble organic solvent include ketones such as acetone, 2-butanone, methyl butyl ketone, and methyl isobutyl ketone; methanol, ethanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, 2- Alcohols such as methoxyethanol; ethers such as tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane; amides such as dimethylformamide, N-methylpyrrolidone, etc. It is preferable to use a compound selected from the group consisting of 6 ketones and alcohols having 1 to 5 carbon atoms.

  Next, the configuration of the fine particle dispersibility evaluation apparatus according to this embodiment will be described. FIG. 1 is a configuration diagram showing the configuration of the fine particle dispersibility evaluation apparatus according to the present embodiment. FIG. 2 is a cross-sectional view showing the configuration of the solution container. FIG. 3 is a configuration diagram showing a main configuration of the fine particle dispersibility evaluation apparatus.

  As shown in FIG. 1, the fine particle dispersibility evaluation apparatus can guide Rayleigh light including fine particle scattered light, which is observed when a solution sample 1 is irradiated with laser light from a laser light source 10, to the detection unit 6. It has a configuration. That is, the fine particle dispersibility evaluation apparatus is a detection unit including a mounting table on which a solution container in which the solution sample 1 is placed, a laser light source 10, a confocal microscopic optical system, a filter optical element 7, a spectroscopic unit, and a light detecting unit. 6. An image processing unit 8 is provided. A condensing lens 11 that condenses the laser beam emitted from the laser light source 10 and a first pinhole 12 disposed on the focal point of the condensing lens 11 are provided on the exit side of the laser light source 10. It has been. As will be described later, the confocal microscopic optical system includes a beam splitter 3 that is a separation optical element, a water immersion objective lens 4, and a second pinhole 5 that is conjugated with the focal plane. Although FIG. 1 shows an inverted microscope, an upright microscope may be used.

  The solution sample 1 is accommodated in a solution container 2 generally called a glass bottom dish. As shown in FIG. 2, the solution container 2 has a hole portion (cover glass 2b) having a diameter of 14 mm at the bottom of a dish portion 2a having a diameter of 35 mm, so that the solution sample 1 can be filled in the dish portion 2a. ing. The thickness of the cover glass 2b in the figure is about 160 to 190 μm, and the aberration is corrected by the immersion lens whose cover glass is corrected.

  The volume of the solution sample 1 required for measurement does not need to be poured into the solution container 2 and is generally in the range of 50 to 500 ml, more preferably in the range of 50 to 250 ml. When the solution sample 1 is less than 50 ml, a sufficient solution depth cannot be obtained at the bottom of the solution container 2 (on the cover glass 2b). If the solution sample 1 exceeds 250 ml, the depth of the solution in the solution container 2 is in millimeters, and light cannot be transmitted according to the Lambert-Beer rule, so that it becomes impossible to acquire fine particle scattered light.

  As shown in FIG. 3, the mounting table 13 is accompanied by a drive unit that scans and moves the mounting table 13 in the XY axis direction as a plane direction as a scanning mechanism. Axial movement is possible. Furthermore, the objective lens holder 14 that holds the water immersion objective lens 4 is accompanied by a drive unit that scans and moves in the Z-axis direction, which is the depth direction, as a scanning mechanism. When it is desired to move in the Z direction while acquiring XY cross-section information by the XY scanning system, the Z-axis direction driving unit provided on the objective lens holder 14 side of the water immersion objective lens 4 is driven. Then, a three-dimensional distribution map of fine particles is created by condensing Rayleigh light including weak fine particle scattered light with the water immersion objective lens 4 while moving the objective lens holder 14 in the Z-axis direction. A scanning mechanism using a piezo element or a stepping motor moving mechanism is generally used as the XY axis direction drive unit 13 and the Z axis direction drive unit of the objective lens holder 14. For the XY axis direction drive unit, it is preferable to use an optical scanning mechanism such as a galvano scanner from the viewpoint of accuracy and measurement time.

  In the above-described state, the fine particle dispersibility evaluation apparatus scans the focal position of the laser beam from the laser light source 10 in the XY direction including the depth (Z) direction of the solution container, thereby including a solution sample containing fine particles. A clear and accurate Rayleigh light profile can be obtained from 1. The spatial resolution in the depth (Z) direction greatly depends on the NA of the water immersion objective lens 4 as will be described later.

  Furthermore, the mounting table 13 of the fine particle dispersibility evaluation apparatus includes a holder 15 as a gripping member for gripping the solution container 2 as shown in FIG. The holder 15 is provided with a shaking mechanism for vibrating the holder 15 and a tilt adjusting mechanism for adjusting the tilt of the solution container 2. The shaking mechanism can be realized by incorporating a piezo mechanism in the holder 15. The tilt adjustment mechanism is such that the bottom surface (cover glass 2b) of the solution container 2 is perpendicular to the laser optical axis (indicated by the alternate long and short dash line in the figure), that is, the XY scanning plane of the laser light and the solution container 2 The inclination of the solution container 2 is adjusted so that the bottom surface of the solution container is kept parallel.

  The laser light emitted from the laser light source 10 is not strongly absorbed by the solution sample 1 and the fine particles to be detected, and the wavelength that is scattered by the fine particles in the solution sample 1 is selected by the Rayleigh scattering mechanism. In addition, the laser beam is generally in a dimmed state using a combination of several ND filters (not shown).

  The conditions under which Rayleigh scattering causes a backscattering mechanism (scattered light returns to the light receiving side of the apparatus) are, in a known technique, a particle size parameter satisfying Rayleigh scattering: Α = πD / λ (D: particle size, λ: The range of (wavelength) is Α <0.4. The wavelength condition of the laser light source 10 satisfying the backscattering can be described by several times the particle diameter. In the present embodiment, when the relationship between the wavelength of the laser light source and the particle size of the fine particles does not satisfy such a condition, a suitable signal cannot be obtained. However, this is not necessary if the particle shape is not a perfect sphere.

  The most efficient generation mechanism of Rayleigh scattering (including back scattering) is as follows. When light with a linearly polarized electric field interacts with particles (molecules), the linearly polarized electric field and an electric field with exactly 180 degrees out of phase (same frequency) that cancels it are placed on a spherical surface. In the case where it appears as a wave of scattered light by interfering with the spherical wave of incident light or other particles. Rayleigh scattering occurs even when general light that is not linearly polarized light is used (for example, natural light), but it has been confirmed that the scattering efficiency is lower than when linearly polarized light is used. In this case, it is preferable that the target particle is theoretically a dielectric, but the target particle in the present embodiment, such as titanium oxide, is a dielectric.

  In the present embodiment, it has been confirmed that this mechanism is particularly effective by using a gas laser having a high extinction ratio as the laser light source 10. However, regardless of the size of the fine particles, the length of the wavelength, and the polarization characteristics, if the difference in refractive index between the fine particles and the aqueous solution (N≈1.33) is small, it is optically transparent and no scattering occurs.

  Furthermore, in general, the higher the laser light intensity of the laser light source 10 is, the stronger the detected intensity of the fine particle scattered light is and the S / N ratio is improved. It is also necessary to decide in consideration of response to light (light emission). Further, if the wavelength of the laser beam is short, in the Rayleigh scattering region, the fine particle scattering intensity increases in inverse proportion to the fourth power of the wavelength.

  The confocal microscopic optical system includes the beam splitter 3, the water immersion objective lens 4, and the pinhole 5 as described above. The beam splitter 3 is a mirror that separates a light beam into two by a dielectric multilayer film. The beam splitter 3 reflects the transmission wavelength range of the laser light emitted from the laser light source 10, irradiates the solution sample 1 on the mounting table 13 with the laser light, and emits fine particle scattered light from the solution sample 1. It has the property of transmitting Rayleigh light including it.

  The water immersion objective lens 4 is a second condenser lens after the condenser lens 11. That is, the water immersion objective lens 4 is configured such that the focus of the laser light coincides with the focus of the water immersion objective lens 4 so that the laser light becomes one point in the solution sample 1. The second pinhole 5 is placed at the back focal point of the water immersion objective lens 4 to efficiently cut off the fine particle scattered light other than the focal point. In order to achieve both high optical system throughput and a small focused beam spot, the irradiation laser diameter to the water immersion objective lens 4 is set to a diameter equal to the incident diameter of the water immersion objective lens 4.

  The spatial resolution in the microscopic optical system greatly depends on the NA of the water immersion objective lens 4 and the confocal pinhole diameter. In the present embodiment, a water immersion objective lens 4 with NA of 1.2 or more is used to achieve high spatial resolution. Further, between the water immersion objective lens 4 and the cover glass 2b of the solution container 2, the emulsion water (not shown) is filled, and the structure is the water immersion objective lens 4 + emulsion water.

  In the fine particle dispersibility evaluation apparatus using an inverted microscope as shown in FIG. 1, laser irradiation and detection are performed by the same water immersion objective lens 4. Since the fine particle scattered light from the depth direction in the solution sample 1 other than the focal point is not focused at the position of the second pinhole 5, the interference light is efficiently cut. As shown in FIG. 1, most of the reflected light in the broken line portion indicating the path of reflected light (scattered light) from the non-focus is shielded by the second pinhole 5. However, since the beam diameter expands in the aqueous solution due to the influence of aberration, it is necessary for measurement to suppress the expansion using the water immersion objective lens 4 or emulsion water.

  The structure of the immersion objective lens + emulsion water is generally filled with distilled water having a refractive index comparable to that of pure water between the immersion objective lens 4 and the solution container 2 to eliminate the influence of air and lens refraction. Ingenuity has been made. In other words, in a dry lens, the medium through which light passes from the lens to the air, the solution container 2 (cover glass 2b), and the solution sample 1 changes, and refraction occurs. On the other hand, when the emulsion water used in combination with the water immersion objective lens 4 is used, the influence (aberration) of light refraction can be eliminated. This is an effective means for increasing the spatial resolution in the solution sample 1 when the immersion objective lens 4 having a large NA is used.

  In the present embodiment, a combination of the immersion objective lens 4 having an NA (numerical aperture) of 1.2 or more and emulsion water is used. If the NA of the water immersion objective lens 4 is not 1.2 or more, the spatial resolution at the time of depth direction analysis cannot be secured. Especially when the particle diameter in the solution is 0.5 μm or less, the fine particle dispersibility evaluation is clear. Becomes impossible.

NA is an important value that determines the performance of the water immersion objective lens, and is a value related to the depth of focus (spatial resolution) and brightness. As NA increases, spatial resolution improves. It is also called NA (= Numerical Aperture) and is represented by the following equation. However, in general, a single objective NA is described for a commercially available objective lens.
NA = n · sinθ
(Here, n is the refractive index of the medium (here, emulsion water) between the solution sample 1 and the objective lens 4, and θ is the angle formed by the optical axis and the light beam entering the outermost side of the immersion objective lens.) In addition, about 1.33 can be used about the refractive index of an emulsion eater.

  Further, as shown in FIG. 1, the confocal microscopic optical system includes a common pinhole (first pinhole 12 and second pinhole 5) having a conjugate relationship with the focal plane of the solution sample 1. It is a focus microscope optical system. That is, the first pinhole 12 is provided between the condenser lens 11 and the beam splitter 3, and the second pinhole 5 is provided in front of the beam splitter 3 and the detection unit 6, so that two pinholes are provided. Are in confocal positions, each having a focal point. As a result, in the confocal microscopic optical system, fine particle scattered light from other than the focal point is blocked by the pinholes 12 and 5. As a result, unnecessary light and fine particle scattered light from the solution sample 1 other than the focal point can be almost completely removed, and excellent spatial resolution in the depth direction can be achieved.

  In the fine particle dispersibility evaluation apparatus of the present embodiment, the laser light intensity is detected from the Rayleigh light component from the solution sample 1 by the ND filter function (not shown) while the laser optical axis is aligned with the solution sample 1. 6 is weak enough to be detected. Next, the Rayleigh light component is detected by the detection unit 6 so that fine particle scattering image information in the XY direction including the depth (Z) direction of the solution sample 1 can be acquired as will be described later.

  The detection unit 6 includes a spectroscopic unit and a light detection unit. Among these, as the spectroscopic means, a spectroscope that separates fine particle scattered light by a prism or a diffraction grating can be cited. The main function is to remove components such as weak fluorescence and Raman light from the solution sample 1 and fine particles as wavelength components. When there is a point (area) conjugate with the focal plane on the optical path immediately before entering the spectroscope, two orthogonal slits (cross slits) are placed in the XY plane of that portion. Thereby, it is possible to make the set of slits play the role of a confocal pinhole (second pinhole 5) in the confocal optical system, and spatial resolution in the X, Y, and Z axis directions is generated.

  Examples of the light detection means include a single channel detector (for example, photomultiplier or APD: Avalanche Photodiode). The fine particle scattered light for evaluating the dispersibility of the fine particles dispersed in the solution sample 1 is very weak. For this reason, it is particularly preferable to use a high-sensitivity detector such as a photomultiplier or APD having a photocathode with high quantum efficiency and having a detection wavelength range including a laser wavelength range. As a result, it is possible to detect weak fine particle scattered light in the solution sample 1 and to evaluate the dispersibility of the fine particles in the deep part of the solution sample 1. The fine particle scattered light that has passed through the second pinhole 5 enters the spectroscope configured in the detection unit 6 and is dispersed, and then is detected by this light detection means.

  Next, the measurement regarding the fine particle dispersibility in the solution sample 1 in the solution container 2 by the fine particle dispersibility evaluation apparatus having the above configuration will be described in detail.

1. Installation of Solution Sample A φ35 mm glass bottom dish used as the solution container 2 is installed, the solution sample 1 in which fine particles are dispersed in the dish portion 2 a is dropped, and this is installed in the holder 15 of the mounting table 13. Then, as shown in FIG. 3, while looking at the acquired image of the XY cross section so that the cover glass 2b surface of the solution container 2 is perpendicular to the laser optical axis indicated by the alternate long and short dash line in the figure, The tilt adjustment mechanism is used to finely adjust the tilt.

  If the surface of the cover glass 2b of the solution container 2 is slightly inclined with respect to the laser optical axis, it is appropriate to obtain a fine particle scattering image of the XY cross section for evaluating sedimentation of the fine particles of the solution sample 1. It may be impossible to acquire a particle scattering image. This is because the focal position of the fine particle confocal optical system is shifted from the cover glass 2b surface during XY scanning, and a fine particle scattering image of the fine particles settled on the cover glass 2b surface cannot be acquired.

2. Acquisition of Fine Particle Scattering Image Information in Solution Sample Next, pure water (not shown) serving as emulsion water is filled between the water immersion objective lens 4 and the cover glass 2b of the solution container 2. A laser beam emitted from the laser light source 10 and diffused through the condenser lens 11 and the first pinhole 12 is guided to the water immersion objective lens 4 through the beam splitter 3. The laser beam guided to the water immersion objective lens 4 passes through the emulsion water and is condensed in the solution sample 1 in the solution container 2.

  The light beam condensed in the solution sample 1 is reflected from the solution sample 1 as light containing fine particle scattered light information, and returns to the beam splitter 3 while being focused through the glass cover 2b, the emulsion water, and the water immersion objective lens 4. . Due to the characteristics of the beam splitter 3, a part of the Rayleigh light including the fine particle scattered light is directed toward the detection unit 6 in the light returned to the beam splitter 3.

  Rayleigh light guided from the beam splitter 3 to the detection unit 6 passes through the filter optical element 7. The Rayleigh light that has passed through the filter optical element 7 further passes through the second pinhole 5 disposed at the condensing position and is guided to the detection unit 6. Then, after entering and dispersing in the spectroscope configured in the detection unit 6, the intensity of the fine particle scattered light is detected by the detection unit 6.

  In such a state, first, the solution container 2 is vibrated by the shaking mechanism (piezo mechanism) in the holder 15 to sufficiently shake the fine particles in the solution sample 1. Thereafter, the inside of the solution sample 1 is scanned with a laser beam by an optical XY scanning system such as a galvano scanner. In parallel, the objective lens holder 14 is scanned in the Z-axis direction by a piezo drive or a stepping motor moving mechanism with respect to the holder 15 holding the solution container 2 containing the solution sample 1 as necessary. As a result, Rayleigh light in the XY directions at a predetermined position of the solution sample 1 is detected. That is, the scattered light intensity profile having the same wavelength as that of the laser light is measured by the detector of the detection unit 6 to extract the scattered image information of the fine particles in the solution sample 1. In this case, the shaking function of the holder 15 is stopped during the measurement.

At this time, in order to be able to acquire Rayleigh light that becomes a fine particle scattering image, the complex refractive index difference between the aqueous solution and the fine particles (titanium oxide) is important, and the following formula: reflectance R = ((N−N1) ² + Κ ² ) / (N + N1) ² + κ ² )
N: Refractive index of fine particles (titanium oxide)
N1: Refractive index of aqueous solution
κ: The reflectance R at the particle interface can be found from the extinction coefficient of the fine particles (titanium oxide). In general, the larger the difference in refractive index, the easier it is to secure scattered light, but in that case, the effect of scattering (absorption in a broad sense: Lambert-Beer's law) will induce a decrease in light transmission. .

  Then, using the detected fine particle scattered light, the fine particle scattered image is plotted for each position in the XYZ including the depth direction, for example, for each position in the depth (Z) direction of the XY cross section. To obtain a fine particle dispersion state profile. With the above processing, it is possible to acquire a fine particle dispersive image under a high spatial resolution condition from the solution sample 1 containing fine particles. As an observation result, if fine particle mapping data in the XY cross section, fine particle mapping data in the XZ cross section, or 3D fine particle mapping data is obtained, the qualitative fine particle dispersion state in the solution sample 1 is evaluated. Is possible.

  Further, the image processing unit 8 can apply a technique such as image analysis to the obtained particle scattering image, for example, a quantification technique such as obtaining a luminance dispersion value for each arbitrary image range. Thereby, the dispersion state of the fine particles in the solution can be evaluated quantitatively.

An example of the quantification method is shown in the flowchart of FIG.
(Step 1)
A fine particle scattering image in the XY cross section is acquired.
(Step 2)
An arbitrary rectangular pixel area having an arbitrary pixel length is determined for the acquired particle scattering image.
(Step 3)
A luminance feature amount (luminance dispersion value, average luminance value, etc.) corresponding to the light intensity of each pixel of the particle scattering image in the pixel region is calculated.
(Step 4)
(Step 2) (Step 3) are repeated, and the dispersion value of the luminance is calculated for a fine particle scattering image within an arbitrary number of pixel regions as shown in FIG. 5, for example. In FIG. 6, the luminance dispersion value in one pixel area is obtained by enlarging the pixel area.
(Step 5)
In each pixel area, the luminance dispersion value or standard deviation value of each pixel is calculated as a feature value in a dispersed state, and a histogram is formed using the feature values in the plurality of pixel areas.
(Step 6)
Correspondence between the histogram and the characteristics of the solution sample in which fine particles are dispersed is taken, and a necessary threshold value is set to determine whether the sample is good or bad.

  At this time, a frequency distribution chart is created with each divided pixel area as one frequency, and a histogram (for example, FIGS. 7A and 7B, in which the vertical axis is the area frequency and the horizontal axis is the feature data section. )). This makes it possible to quantitatively determine the “dispersibility: bad” sample with respect to the “dispersibility: good” sample having good dispersibility, for example, by setting a threshold value. It is also possible to quantitatively determine which area (area) in the sample is poorly distributed by creating a histogram in which the vertical axis is a feature amount and the horizontal axis is a labeled pixel area. Become.

  In the quantification method described above, an arbitrary pixel region can be changed because a remarkable range of the aggregation state varies depending on the particle size and content ratio of the fine particles, and the range is preferably rectangular. This is based on an algorithm in which humans visually evaluate the pixel & luminance density of an image, and when a human evaluates a fine area, the luminance variation of a narrow area is observed, and when a domain of large luminance unevenness is viewed. This is based on viewing the luminance variation in a wide area. Further, as the feature value in the dispersed state, it is preferable to obtain a luminance dispersion value or a luminance standard deviation for each pixel region. Thereby, dispersibility evaluation of the fine particles in the solution can be performed satisfactorily.

Hereinafter, the fine particle dispersibility evaluation apparatus and the fine particle dispersibility evaluation method according to the present embodiment will be described based on examples and comparative examples.
[Example 1]
Under the following conditions, the titanium oxide fine particle dispersibility evaluation of the solution sample (white ink) in which the fine particles are dispersed was performed.
(1) Solution sample (white ink)
As a solution sample 1, a white ink in which titanium oxide fine particles having a primary particle diameter of 0.25 μm were dispersed in a liquid containing a pigment dispersant, a binder, and water was prepared.

(2) Fine particle dispersibility evaluation apparatus Configuration shown in FIG. 1; laser light source 10; laser light wavelength 488 nm
Water immersion objective lens 4; water immersion objective lens (Nikon CFI Plan Apo 60 × NA = 1.25 (filled between the cover glass 2b and the objective lens 4 with emulsion water having a refractive index of 1.33)
In addition, the refractive index of emulsion water used the complex refractive index (N = 1.333, (kappa = 0)) of general pure water as it was.

(3) Measurement procedure First, an appropriate amount of solution sample 1 (white ink) in which titanium oxide fine particles are dispersed is dropped onto the solution container 2 with a micropipette, and the solution container 2 is held and mounted by a holder 15 having a shaking function. Place on the table 13. At this time, the solution sample 1 is shaken by a shaking function (piezo vibration mechanism) until immediately before the measurement, and the titanium oxide fine particles in the solution sample 1 are uniformly dispersed. Next, with the apparatus configuration shown in FIG. 1, a water immersion objective lens 4 is prepared, and emulsion water (not shown) is filled between the solution sample 1 containing fine titanium oxide particles. It is preferable to stop the shaking function after the emulsion water is filled. Since the measurement can be performed quickly thereafter, there is almost no need to worry about sedimentation of fine particles.

  Then, the light beam of the laser excitation light from the laser light source 10 is condensed by the water immersion objective lens 4, and the position in the depth direction (Z direction) several μm from the cover glass 2b surface of the solution container 2 on which the solution sample 1 is dropped. Irradiate. The solution sample 1 in the solution container 2 is scanned in the XY direction by a galvano scanner, and a scattered image of weak titanium oxide fine particles from the solution sample 1 is guided to the detector of the detection unit 6 (photoelectric surface is GaAsP APD). A fine particle scattering image was obtained.

  FIG. 5 is an example of a fine particle scattering image (XY cross section) acquired from the solution sample 1 in which titanium oxide fine particles are dispersed, and is a diagram showing a 155 × 155 μm region with 512 × 512 pixels and 256 gradations. . FIG. 5 is a diagram showing an example in which an arbitrary pixel region of 40 × 40 pixels is specified in the acquired particle scattering image. As can be seen from the results shown in FIG. 5, it was confirmed that titanium oxide fine particles having a primary particle diameter of 0.25 μm were uniformly dispersed in the solution sample.

  Further, in the image processing unit 8, processing by a quantification method was performed according to the flow shown in FIG. Here, an arbitrary pixel area of 40 pixels in the horizontal direction and 40 pixels in the vertical direction is determined with respect to the acquired image shown in FIG. The variance value of was calculated. By repeating this, the variance value of the luminance was calculated in an arbitrary number of pixel regions, and a histogram (FIG. 7 shows an example of the result) was created. By measuring samples with good dispersibility and bad samples of titanium oxide fine particles in a large number of aqueous solutions, threshold values for good / bad evaluation were selected on the histogram. Thereby, the dispersibility of the titanium oxide fine particles in the solution sample 1 was quantitatively evaluated.

[Example 2]
As in the first embodiment, the luminous flux of the laser excitation light from the laser light source 10 is condensed by the water immersion objective lens 4, and the depth direction (from the cover glass 2b surface of the solution container 2 onto which the solution sample 1 is dropped) Irradiate a position of several μm in the Z direction). The solution sample 1 in the solution container 2 is scanned in the XY direction by a galvano scanner, and a scattered image of weak titanium oxide fine particles from the solution sample 1 is guided to the detector of the detection unit 6 (photoelectric surface is GaAsP APD). A fine particle scattering image was obtained. FIG. 8 is an example of a fine particle scattering image (XY cross section) acquired from the solution sample 1 in which titanium oxide fine particles are dispersed. Thereafter, in the image processing unit 8, processing by a quantification method was performed according to the flow shown in FIG. 4 to quantitatively evaluate the fine particle dispersibility.

  At this time, the surface of the cover glass 2b of the solution container 2 carried on the holder 15 on the mounting table 13 was inclined under the condition that the pin hole size was reduced and the optical spatial resolution was shallow. Therefore, the tilt correction of the cover glass 2b surface of the solution container 2 was performed in advance using a tilt adjustment mechanism built in the holder 15 for the evaluation of sedimentation. Thereby, an appropriate fine particle scattering image can be acquired for the titanium oxide fine particles settled on the cover glass 2b surface of the solution container 2, and the sedimentation state of the titanium oxide fine particles over time can be known.

[Comparative Example 1]
A fine particle scattering image was acquired in the same manner as in Example 1 by using a holder that does not have a shaking function as the holder 15 that holds the solution container 2. Immediately after setting the solution container 2 to which the solution sample 1 is dropped, titanium oxide fine particles that become a metal oxide having a high specific gravity begin to settle, and as shown in FIG. 9, dispersed titanium oxide fine particles in the solution sample 1 No suitable fine particle scattering image could be obtained.

[Comparative Example 2]
A conventional apparatus for evaluating fine particle dispersibility in a solution sample 1 having a configuration that does not include an image processing section 8 that performs image processing for quantitative evaluation of fine particle dispersibility based on the intensity of light detected by a light detection means is used. It was. However, it is impossible to calculate the dispersion value of the luminance of the acquired multi-pixel / multi-value image with an arbitrary pixel size by using the analysis software mainly for image measurement equipped as a standard equipment on the market. Therefore, it was not possible to perform quantification using luminance information in the acquired image representing the presence of the obtained titanium oxide fine particles.

[Comparative Example 3]
As in the first embodiment, the laser excitation light beam is condensed by the water immersion objective lens 4 and irradiated to one point on the bottom surface of the cover glass 2b of the solution container 2 onto which the solution sample 1 in which the fine particles are dispersed is dropped. Scan in the XY direction by a galvano scanner. A scattering image of weak titanium oxide fine particles from the solution sample 1 in a settling state was guided to a detector (APD having a photocathode of GaAsP on the photocathode) of the detection unit 6 to obtain a fine particle scattering image.

  At this time, the tilt adjustment mechanism of the solution container 2 was not provided without providing the tilt adjustment mechanism in the holder 15, but the inclination of the bottom surface (cover glass 2 b) of the solution container held by the holder 15 on the mounting table 13 was not achieved. there were. Therefore, in the fine particle scattering image in the XY direction on the surface in contact with the bottom surface of the solution container 2 (the cover glass 2b), a part of the measurement point at the time of scanning has moved away from the cover glass 2b surface. As a result, an appropriate fine particle scattering image could not be acquired, for example, the fine particle scattering XY two-dimensional image was interrupted.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A holding member such as a holder 15 for holding a solution container such as a solution container 2 in which a solution sample such as a solution sample 1 in which fine particles are dispersed in a solution, a laser light source such as a laser light source 10, and a laser beam on the solution sample. In a conjugate relationship with a separation optical element such as a beam splitter 3 that receives Rayleigh light including weak fine particle scattered light from a solution sample, a water immersion objective lens such as a water immersion objective lens 4, and a focal plane. A confocal microscopic optical system having pinholes such as certain pinholes 5 and 12, a filter optical element such as a filter optical element 7 that transmits Rayleigh light in light that has passed through the separation optical element, and light that has passed through the filter optical element A spectroscopic means for splitting the light, a light detecting means such as a detecting section 6 for detecting the intensity of the light split by the spectroscopic means, and a laser beam as a solution sample In contrast, in the fine particle dispersibility evaluation apparatus, which includes a scanning mechanism capable of relatively scanning in the depth direction and the plane direction of the solution sample, and evaluates the dispersibility of the fine particles in the solution sample, the solution container held by the holding member A two-dimensional image data in the depth direction and the plane direction is constructed based on the shaking mechanism for shaking the light and the intensity of the light detected by the light detection means, and an image for quantitative evaluation of the fine particle dispersibility from the data And an image processing unit such as an image processing unit 8 that performs processing.
According to this, as described in the above embodiment, the solution sample in the solution container is shaken by the shaking mechanism, so that the settling of the fine particles in the solution sample is suppressed, and the dispersion state of the fine particles is set appropriately. It becomes possible to evaluate. As can be seen from the experimental results, the image processing unit can quantitatively evaluate the dispersion state of the fine particles from the image data indicating the presence of the fine particles. As a result, an accurate dispersion state of the fine particles dispersed in the solution can be obtained easily and quickly in a high concentration state without preparing a diluted solution.

(Aspect B)
In the fine particle dispersibility evaluation apparatus according to (Aspect A), the gripping member has a tilt adjustment mechanism for leveling the bottom surface of the solution container.
According to this, as described in the above embodiment, the tilt adjustment mechanism performs fine adjustment of the tilt of the solution container in advance, and the parallel (X-Y) scanning plane of the laser beam and the bottom of the solution container containing fine particles are parallel. Can keep. This makes it possible to acquire an appropriate fine particle scattering image of the fine particles that have settled on the bottom surface of the solution container. In particular, it is possible to appropriately evaluate the sedimentation state of the fine particles over time.

(Aspect C)
In the fine particle dispersibility evaluation apparatus according to (Aspect A) or (Aspect B), the image processing unit may determine the depth distribution of the Rayleigh light in the depth direction or the planar direction of the solution sample for each depth position by the fine particle scattered light. A fine particle scattering image is acquired, a plurality of arbitrary pixel regions of the fine particle scattering image are determined, a luminance dispersion value or a standard deviation value of each pixel is calculated as a feature value of the dispersion state in each pixel region, and the plurality of pixels Histogram of region feature values.
According to this, as described in the above embodiment, since it is possible to quantitatively evaluate the dispersion state of the fine particles dispersed in the solution, the dispersion state of the fine particles can be increased without preparing a diluted solution. It can be obtained easily and quickly in the concentration state.

(Aspect D)
In the fine particle dispersibility evaluation apparatus according to (Aspect C), the pixel range of the pixel region is rectangular, and the number of vertical and horizontal pixels can be freely changed.
According to this, as described in the above embodiment, it is possible to cope with the remarkable range of the aggregation state depending on the particle size / content ratio of the fine particles, and appropriately evaluate the dispersion state of the fine particles dispersed in the solution. be able to.

(Aspect E)
In (Aspect C), the image processing unit histograms the feature quantities in the dispersed state in each pixel area that is sequentially labeled, and determines pass / fail for each pixel area by setting a numerical threshold value of the feature quantities.
According to this, as described in the above embodiment, it is possible to quantitatively evaluate which place in the solution sample is poorly dispersed.

(Aspect F)
In (Aspect C), the image processing section creates a histogram by creating a frequency distribution diagram in which each area is plotted as one frequency within a numerical value range determined by the feature value of the dispersion state in each pixel area, The quality of the distributed state is determined by setting a threshold value in the numerical value range.
According to this, as described in the above embodiment, for example, it is possible to quantitatively determine “a sample with poor dispersibility” for a “sample with good dispersibility” with good dispersibility.

(Aspect G)
A confocal microscopic optical system having a separation optical element, a water immersion objective lens, and a pinhole conjugated with a focal plane irradiates a solution sample in which fine particles are dispersed in the solution with laser light. In a fine particle dispersibility evaluation method that receives light including fine particle scattered light from a particle, detects the intensity of Rayleigh light contained in the fine particle scattered light, and evaluates the fine particle dispersion state, a solution container in which the solution sample is accommodated After shaking, the laser beam is irradiated in the depth direction and the plane direction of the solution sample, and two-dimensional image data relating to the depth direction and the plane direction is constructed based on the intensity of the Rayleigh light. Perform quantitative evaluation of dispersibility.
According to this, as described in the above embodiment, the solution sample in the solution container is shaken by the shaking mechanism, so that the settling of the fine particles in the solution sample is suppressed, and the dispersion state of the fine particles is set appropriately. It becomes possible to evaluate. As can be seen from the experimental results, the image processing unit can quantitatively evaluate the dispersion state of the fine particles from the image data indicating the presence of the fine particles. As a result, an accurate dispersion state of the fine particles dispersed in the solution can be obtained easily and quickly in a high concentration state without preparing a diluted solution.

DESCRIPTION OF SYMBOLS 1 Solution sample 2 Solution container 3 Beam splitter 4 Water immersion objective lens 5 Second pinhole 6 Detection part 7 Filter optical element 8 Image processing part 10 Laser light source 11 Condensing lens 12 First pinhole 13 Mounting base 14 Lens holder 15 holder

JP 2014-13228 A

Claims (13)

Rayleigh including a gripping member for holding a solution container containing a solution sample in which fine particles are dispersed in a solution, a laser light source, laser light to the solution sample, and weak fine particle scattered light from the solution sample Separation optical element for receiving light, water immersion objective lens, and confocal microscopic optical system having pinholes conjugate to the focal plane, and filter optical element for transmitting Rayleigh light in the light passing through the separation optical element A spectroscopic unit that splits the light transmitted through the filter optical element, a photodetection unit that detects the intensity of the light split by the spectroscopic unit, and the depth of the solution sample with respect to the solution sample. A fine particle dispersibility evaluation apparatus for evaluating dispersibility of fine particles in a solution sample, comprising a scanning mechanism capable of scanning relatively in a direction and a plane direction,
A shaking mechanism for shaking the solution container held by the holding member;
An image processing unit that constructs two-dimensional image data in the depth direction and the plane direction based on the intensity of light detected by the light detection means, and performs image processing for quantitative evaluation of fine particle dispersibility from the data; ,
A fine particle dispersibility evaluation apparatus, wherein the solution sample is irradiated with linearly polarized laser light .   In the fine particle dispersibility evaluation apparatus according to claim 1,
A fine particle dispersibility evaluation apparatus using a gas laser as the laser light source .   In the fine particle dispersibility evaluation apparatus according to claim 1 or 2,
Fine particle dispersibility, wherein the solution sample is a solution containing an inorganic white pigment and water Evaluation device.   In the fine particle dispersibility evaluation apparatus according to claim 3,
The fine particle dispersibility evaluation apparatus, wherein the inorganic white pigment is titanium oxide.   In the fine particle dispersibility evaluation apparatus according to claim 4,
The titanium oxide is titanium oxide having an average particle size of 100 to 500 nm. Particle dispersibility evaluation device.   In the fine particle dispersibility evaluation apparatus according to any one of claims 3 to 5,
The solution sample contains a binder, and the fine particle dispersibility evaluation apparatus.   In the fine particle dispersibility evaluation apparatus according to claim 6,
  The fine particle dispersibility evaluation apparatus, wherein the binder is a urethane resin.   In the fine particle dispersibility evaluation apparatus according to claim 7,
The solution sample is ink;
Fine particles characterized in that the content of the urethane resin with respect to the total amount of the ink is 1 to 20% by mass Child dispersibility evaluation device. In the fine particle dispersibility evaluation apparatus according to any one of claims 1 to 8 ,
The fine particle dispersibility evaluation apparatus, wherein the gripping member has a tilt adjustment mechanism for leveling a bottom surface of the solution container. In the fine particle dispersibility evaluation apparatus according to any one of claims 1 to 9 ,
The image processing unit obtains a fine particle scattered image at each depth position by the fine particle scattered light from the distribution of Rayleigh light intensity in the depth direction or the planar direction of the solution sample, and selects an arbitrary pixel region of the fine particle scattered image. Fine particle dispersibility evaluation, characterized by calculating a plurality of pixel dispersion values or standard deviation values as feature values in a dispersed state in each pixel region, and generating a histogram of the feature values in the plurality of pixel regions apparatus. In the fine particle dispersibility evaluation apparatus according to claim 10 ,
The fine particle dispersibility evaluation apparatus according to claim 1, wherein the pixel range of the pixel region is rectangular, and the number of vertical and horizontal pixels can be freely changed. In the fine particle dispersibility evaluation apparatus according to claim 10 ,
The image processing unit generates a histogram of the feature values of the dispersion state in each of the sequentially labeled pixel regions, and determines the quality of each pixel region by setting a numerical threshold value of the feature amount. Sex evaluation device. In the fine particle dispersibility evaluation apparatus according to claim 10 ,
The image processing unit creates a histogram by creating a frequency distribution chart in which each area is plotted as one frequency within a numerical value range determined by the feature value of the dispersion state in each pixel area, and sets a threshold value in the numerical range of the feature value. A fine particle dispersibility evaluation apparatus characterized by determining whether the dispersion state is good or not by setting.