JP2006159166A - Particle accumulation body and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-quality particle aggregate and its manufacturing method. <P>SOLUTION: This invention is to provide a particle aggregate constituted by densely aggregated particles. The method includes a process for preparing a particle dispersed solution 20 where particles 22 are dispersed in a first solvent 24, a process for arranging the dispersed solution 20 in a second solvent 30 capable of separating the dispersed solution 20 from the first solvent 24, and a process for spreading the first solvent 24, which is contained in the particle dispersed solution 20 in the second solvent 30, into the second solvent 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a particle assembly in which spherical particles are densely integrated. The present invention also relates to a method for producing a particle assembly in which particles are densely accumulated. Furthermore, the present invention relates to a particle assembly material in which such a particle assembly is disposed on the surface of a substrate and a method for producing the same.

Aggregates of a plurality of particles have been widely studied because they can be materials that exhibit useful properties different from those of a single particle. For example, a particle aggregate in which fine particles are aggregated with a high degree of regularity can be a useful material in photonic crystals and other fields.
Patent Document 1 describes a technique in which a substrate is immersed in a suspension containing fine particles, and the substrate is slowly pulled up from the suspension to form a single-layer fine particle film on the substrate surface. Patent document 2 is mentioned as another prior art document regarding the aggregate | assembly of microparticles | fine-particles.

JP-A-8-234007 JP 2002-341161 A

  In the technique described in Patent Document 1, a film-like particle aggregate is formed on the surface of a substrate by pulling up particles in a liquid phase (suspension) together with the substrate into a gas phase. However, this technique cannot be applied to the production of a particle aggregate having an arbitrary two-dimensional shape. In addition, since it is difficult to stably control the state of the interface between the gas phase and the liquid phase, defects are likely to occur in the arrangement of the particles constituting the particle aggregate.

  The present invention relates to a particle aggregate (cluster) in which particles are densely integrated, and a high-quality particle aggregate (for example, a particle aggregate satisfying at least one of few defects and high regularity of arrangement) ) Is one purpose. Another object of the present invention is to provide a new and useful method suitable for the production of a particle assembly in which particles are densely integrated. Yet another object is to provide a particle assembly material in which such a particle assembly is disposed on the surface of a substrate and a method for producing the same.

  The present inventor has found that the above problem can be solved by utilizing the interface between the liquid phase and the liquid phase (liquid-liquid interface) instead of the interface between the gas phase and the liquid phase (gas-liquid interface). The present invention has been completed.

According to one invention disclosed herein, a particle assembly is provided in which substantially monodispersed spherical particles are densely integrated. The particle aggregate has a spherical outer shape. The average diameter d of the spherical particles constituting the aggregate is 10 μm or less. The ratio (r / d) between the radius r of the particle aggregate itself and the average diameter d of the spherical particles constituting the aggregate is in the range of about 5-50. The particle aggregate focuses on individual particles constituting the spherical surface of the aggregate, and the particles are surrounded by five spherical constituent particles (that is, in-plane five-coordinate particles). (P ₅ )), the particles surrounded by six spherical surface constituent particles (in-plane six-coordinate particles (P ₆ )), and the particles surrounded by seven spherical constituent particles and are those when classified into three kinds of the (plane 7 coordination of the particles (P _7)), the number of particles corresponding to the P ₆ and the number of particles (N _P5) corresponding to the P ₅ (N _P6 ) And the number of particles corresponding to P ₇ (N _P7 ) satisfy the following formula: 10% <{(N _P5 + N _P7 ) / (N _P5 + N _P6 + N _P7 )} <30%;
Such a particle aggregate is an aggregate in which a relatively large number of fine particles are accumulated, but is excellent in the regularity of particle arrangement on the sphere surface. That is, the agglomerate has a high quality spherical surface that is closely packed with particles. Such an aggregate is useful in various fields.

According to another invention disclosed herein, there is provided a particle aggregate in which substantially monodispersed spherical particles are densely accumulated, and the particles are accumulated in a predetermined two-dimensional pattern on a substrate surface. A particle aggregate is provided. Here, the “two-dimensional pattern” refers to the shape (pattern) of the aggregate when the particle aggregate accumulated on the surface of the substrate is viewed from a direction perpendicular to the surface. The average diameter d of the spherical particles constituting the aggregate is 10 μm or less. The aggregate satisfies at least one of the following (A) and (B).
(A) The pattern has a portion where the virtual contour line is linear, and the standard deviation S of the distance from the center of the particles constituting the outer edge of the aggregate to the virtual contour line in the linear portion. Is 1 × 10 ⁻² μm or less.
(B) In the pattern, the virtual contour has an arc-shaped portion, and the standard deviation S of the distance from the center of the particles constituting the outer edge of the aggregate to the virtual contour in the arc-shaped portion. Is 5 × 10 ⁻¹ μm or less.
Here, with respect to the above (A), “the part where the virtual contour line is a straight line” means that the position of the center of the particle constituting the outer edge of the particle aggregate is well approximated by a linear line (virtual contour line). Refers to the part. With respect to (B) above, “the part where the virtual contour line has an arc shape” refers to a part in which the center of the particles constituting the outer edge of the particle assembly is well approximated by an arc (virtual contour line).
Such a particle assembly has good clarity of the outer edge (contour) of the two-dimensional pattern and regularity of particle arrangement. Thus, the high-quality particle aggregate is highly useful.

According to another invention disclosed herein, there is provided a method for producing a particle assembly in which particles are densely integrated. The method includes a step of preparing a particle dispersion in which the particles are dispersed in a first solvent. Moreover, the process of arrange | positioning the said particle dispersion liquid in the 2nd solvent which can be phase-separated with said 1st solvent is included. Then, in the second solvent, the first solvent (that is, the dispersion medium of the particles) contained in the dispersion is first maintained while maintaining the particles contained in the dispersion in the substantially arranged state. Diffusing in two solvents.
When the particle dispersion is disposed in the second solvent, a liquid-liquid interface is formed between the particle dispersion (first solvent) and the second solvent. As the first solvent contained in the dispersion gradually diffuses into the second solvent, the particles left behind from the diffusion are densely accumulated to form a particle aggregate.

The above production method can be applied, for example, to produce a particle aggregate on a suitable substrate surface. That is, according to another invention disclosed herein, there is provided a method for producing a particle aggregate formed by densely collecting particles on a substrate surface. The manufacturing method includes a step of preparing a particle dispersion in which the particles are dispersed in a first solvent, a step of applying the dispersion to the surface of the base material, and a first phase that can be phase-separated from the first solvent. Disposing the substrate in two solvents. Here, the step of applying the particle dispersion to the surface of the substrate may be performed before the substrate is disposed in the second solvent, or may be performed after the substrate is disposed in the second solvent. Good. The manufacturing method further includes a step of diffusing the first solvent contained in the dispersion into the second solvent while leaving the particles contained in the dispersion on the substrate on the surface of the base material in the second solvent. including. As a result, the particles left behind from the diffusion are densely accumulated to form a particle aggregate.
According to this method, it is possible to appropriately manufacture a particle aggregate in which particles are densely integrated using a liquid-liquid interface formed between the particle dispersion (first solvent) and the second solvent. .

  In one preferred embodiment of the production method, the surface of the substrate to which the dispersion is applied is patterned so that the affinity of the predetermined region for the first solvent is higher than that of the periphery of the region. By applying the particle dispersion to the surface of the substrate thus patterned, the particle dispersion can be preferentially (preferably selectively) arranged in the predetermined region. By diffusing the first solvent contained in the dispersion liquid arranged in this manner into the second solvent, a particle aggregate can be formed preferentially (preferably selectively) in the predetermined region.

  Preferable examples of particles used in these production methods include particles having a relatively sharp particle size distribution (preferably substantially monodispersed particles, in other words, particles having a substantially uniform particle size). It is done. Further, it is preferable to use spherical particles, and it is more preferable to use substantially spherical particles. When particles having such a particle size distribution and / or shape are used, the effect of employing the production method of the present invention can be exhibited particularly well. For example, a particle aggregate with better regularity of particles (with fewer alignment defects), a particle aggregate with denser particles, or a particle aggregate with a clearer contour One or more of the above can be realized. That is, a higher quality particle aggregate can be produced.

Another invention disclosed herein is a particle assembly material in which a particle assembly in which particles are densely integrated is arranged on a substrate surface (that is, a substrate and particles arranged on the substrate surface). A method for manufacturing a substrate having an integrated body is provided. The manufacturing method includes a step of preparing a particle dispersion in which the particles are dispersed in a first solvent. Moreover, the process of providing the said dispersion liquid on the surface of the said base material is included. Moreover, the process of arrange | positioning the said base material in the 2nd solvent which can be phase-separated with said 1st solvent is included. Here, the step of applying the particle dispersion to the surface of the substrate may be performed before the substrate is disposed in the second solvent, or may be performed after the substrate is disposed in the second solvent. Good. The manufacturing method further diffuses the first solvent contained in the dispersion into the second solvent while leaving the particles contained in the dispersion on the substrate surface in the second solvent in the second solvent. Process. As a result, the particles left behind from the diffusion are densely accumulated to form a particle aggregate.
According to such a method, the particle accumulation having a particle accumulation body in which particles are densely accumulated on the substrate surface by utilizing a liquid-liquid interface formed between the particle dispersion (first solvent) and the second solvent. A body material can be manufactured appropriately.

The above method can be preferably applied as a method for producing a particle assembly material in which the particle assembly is disposed in a predetermined region of the substrate. For example, in the manufacturing method described above, a substrate that is patterned so that the affinity of the predetermined region for the first solvent is higher than that around the region is used, and the particle dispersion is applied to the surface of the substrate. . Thereby, the particle aggregate material in which the particle aggregate is arranged corresponding to the predetermined region is manufactured. According to this aspect, the particle assembly material in which the particle assembly is formed preferentially (preferably selectively) in the predetermined region can be appropriately manufactured. Further, using a base material formed so that two or more of the predetermined regions constitute a predetermined pattern (array), a patterning (array) composed of particle aggregates arranged corresponding to the pattern is formed. Can be produced.
Any of the methods described above can be applied to the production of particle aggregates having various two-dimensional patterns (two-dimensional shapes) and particle aggregate materials provided with the aggregates on a substrate. Further, the present invention can be applied to particle aggregate patterning in which two or more particle aggregates are arranged in various arrangements (array patterns), and production of a particle aggregate material provided with the patterning on a substrate. Such a method includes, for example, a particle aggregate patterning composed of a plurality of particle aggregates arranged in two or more directions on a substrate surface, and a particle aggregate material having the patterning on the substrate (that is, the substrate and the substrate). This method is suitable as a method for manufacturing a substrate having a particle aggregate patterning disposed on a material surface.

  Hereinafter, specific embodiments relating to the present invention will be described, but the present invention is not intended to be limited to the specific examples. In addition, technical matters other than the contents specifically mentioned in the present specification and necessary for the implementation of the present invention can be understood as design matters for those skilled in the art based on the prior art. The present invention can be carried out based on the technical contents disclosed in the present specification and drawings and the common general technical knowledge in the field.

  The method disclosed herein comprises a two-component system in which a phase of a first solvent (particle dispersion) is disposed in a phase of a second solvent, and then diffusing the first solvent into the second solvent. It has the feature of collecting particles using the liquid-liquid interface. As long as it has such characteristics, the method disclosed herein can be carried out in various modes regardless of the characteristics (material, external shape, particle size distribution, etc.) of the particles used. For example, it can implement in the aspect which uses particle | grains about 0.1-100 micrometers in diameter. Use of particles having a diameter of about 0.1 to 20 μm is more preferable, and particles having a diameter of about 0.2 to 10 μm are more preferable. From the viewpoint of obtaining a denser particle aggregate, it is preferable to use particles having a smooth (small unevenness) outer shape. Particles having a shape close to a sphere (spherical particles) are preferred, and substantially spherical particles are particularly preferred. In order to obtain a high quality (in other words, a more desirable accumulation state), it is usually advantageous to use particles having a relatively sharp particle size distribution. For example, particles having a standard deviation of the particle size distribution of 0.5 μm (50%) or less can be preferably used. Particles with a standard deviation of 0.2 μm (20%) or less are more preferred, and particles with a standard deviation of 0.1 μm (10%) or less are more preferred. It is particularly preferred to use substantially monodispersed (ie, substantially uniform particle size) particles.

The invention disclosed herein can be applied to a particle aggregate including any one of inorganic particles made of metal, ceramic, and the like, and organic particles made of resin and the like. For example, ceramic materials such as SiO ₂ , TiO ₂ , BaTiO ₃ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, etc., gold (Au), silver (Ag), copper (Cu), nickel (Ni) or these Particles mainly composed of a metal material such as an alloy of the above, a polymer material such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polystyrene, or the like can be used. Particles whose surface is appropriately chemically modified or modified may be used. It is preferable to select particles made of a material that is stable (for example, hardly causes chemical reaction, dissolution, swelling, etc.) with respect to both the first solvent and the second solvent described later. Two or more kinds of particles having different characteristics (material, outer shape, particle size distribution, etc.) may be used in combination.

A particle aggregate is produced using a particle dispersion in which the particles are dispersed in a first solvent. As the first solvent, it is preferable to use a solvent that gives a dispersion having good dispersion stability in consideration of the type of particles to be used. In order to improve the dispersion stability, an appropriate amount of a general dispersant may be contained in the particle dispersion.
Although it does not specifically limit, the particle concentration in this particle dispersion can be about 0.01-100 mg / mL, for example. Usually, it is appropriate that the particle concentration is about 0.1 to 10 mg / mL. The preferred particle concentration may vary depending on the three-dimensional shape (single particle layer, multi-particle layer, sphere, etc.), size (diameter, area, etc.), production conditions, etc. of the target particle aggregate. For example, when producing a particle aggregate consisting of a single particle layer on the surface of a substrate, a particle dispersion having a relatively low particle concentration (for example, about 0.01 to 0.1 mg / mL) is usually used. It is preferable.

  In the present invention, the first solvent and the second solvent are selected and used so as to be an appropriate combination. That is, the first solvent and the second solvent are selected so as to be a combination that can form a liquid-liquid interface between the two solvents (a combination in which both solvents can be phase-separated or a combination that is not uniformly mixed). Each of the first solvent and the second solvent may be a solvent composed of one kind of solvent selected from known organic solvents and inorganic solvents, or a mixed solvent composed of two or more kinds of solvents that are uniformly mixed. There may be. Usually, it is preferable to use a first solvent composed of one type of solvent and a second solvent composed of another type of solvent.

A suitable combination of the first solvent and the second solvent may vary depending on the production conditions of the particle aggregate, the shape of the target particle aggregate, and the like. Although not particularly limited, for example, in the case of forming a relatively large spherical particle aggregate on the substrate surface, in the case of forming a relatively thick (multilayer) particle aggregate on the substrate surface, etc. In the production conditions in which the base material is disposed in the second solvent with the surface to which the dispersion is applied, the specific gravity of the first solvent and the second solvent is approximately the same, or the specific gravity of the first solvent is that of the second solvent. Good results are likely to be obtained by making the combination slightly smaller than the specific gravity. On the other hand, in the production conditions in which the substrate is placed in the second solvent with the surface to which the dispersion is applied, the first solvent and the second solvent have the same specific gravity or the first solvent has a second specific gravity. Good results are easily obtained by using a combination that is slightly larger than the specific gravity of the solvent.
On the other hand, when forming a particle aggregate having a predetermined two-dimensional shape on the substrate surface, when forming a particle aggregate with a uniform thickness over a relatively wide area of the substrate surface, the substrate surface is relatively thin. In the case of forming a particle aggregate (for example, about one particle layer to two particle layers), etc., in the manufacturing conditions in which the base material is disposed in the second solvent with the surface to which the dispersion is applied facing upward, A favorable result is easily obtained when the specific gravity of the one solvent and the second solvent is approximately the same, or the specific gravity of the first solvent is slightly larger than the specific gravity of the second solvent.
In addition, in the case where the particle aggregate is formed in a state where the droplets of the first solvent are dispersed (floating) in the second solvent, a combination in which the specific gravity of the first solvent and the second solvent is approximately the same. It is preferable that

  In one preferred embodiment disclosed herein, one of the first solvent and the second solvent can be selected from a hydrophilic solvent and the other can be selected from a hydrophobic solvent. As the hydrophilic solvent, one or two selected from water, lower alcohol (for example, alkyl alcohol having about 1 to 3 carbon atoms), N, N-dimethylformamide, tetrahydrofuran, dimethylsulfoxide, nitromethane, N-methylpyrrolidone and the like. More than seeds can be used. Examples of the hydrophobic solvent include aliphatic hydrocarbons (for example, chain hydrocarbons having about 6 to 12 carbon atoms (hexane, etc.), alicyclic hydrocarbons having about 6 to 12 carbon atoms (decalin, etc.). ), Ethers (diisopropyl ether, etc.), aromatic hydrocarbons (benzene, toluene, etc.) or the like can be used. From the viewpoint of ease of operation, etc., it is usually preferable to select a solvent having a boiling point of about 40 ° C. or higher and a freezing point of about 20 ° C. or lower as the first solvent and the second solvent.

  The method of the present invention is suitable as a method for producing a particle aggregate on the surface of an arbitrary substrate. The material and shape of the base material to be used are not particularly limited. For example, using a substrate mainly composed of one or more materials selected from silicon (Si), glass, metal (copper, aluminum, etc.), ceramic (alumina, etc.), and polymer (PMMA, etc.). Can do. A base material made of a material that is stable (for example, hardly causes chemical reaction, dissolution, swelling, etc.) with respect to both the first solvent and the second solvent is preferable.

  In one preferred embodiment, a substrate having a surface treatment applied to a partial range or almost the entire range of the surface to which the dispersion is applied is used. A particle dispersion is applied to the surface-treated surface to form a particle aggregate. By performing such a surface treatment, the uniformity of the substrate surface is increased, the affinity of the substrate surface with respect to the first solvent is adjusted (the affinity is increased or decreased), the predetermined region on the substrate surface and the region Patterning the substrate surface so that the affinity for the first solvent is different from the surroundings of the region (the affinity of the predetermined region is made higher or lower), etc. The effect of can be obtained. Alternatively, the particle aggregate may be formed directly on the surface of the base material itself made of the above material or the like (that is, on the surface where the material constituting the base material is exposed) without performing such surface treatment. .

  Various surface treatment methods (or surface modification methods) can be employed as a method for subjecting the substrate surface to surface treatment, depending on the material of the substrate, the purpose of the surface treatment, and the like. As an example of a preferable method, there is a method of applying a desired coating (forming a film) to the surface of the substrate. For example, it is preferable to apply a so-called hydrophobic coating or a hydrophilic coating. The method for applying such a coating is not particularly limited. For example, an appropriate coating agent may be applied to almost the front surface of the substrate surface or an arbitrary range of the surface. As means for applying the coating agent, conventionally known application means such as dipping, doctor blade application, roller application, spray application, brush application, screen printing, embossing, and photolithography can be appropriately employed. If necessary (for example, when a coating agent is applied to an arbitrary range of the substrate surface), two or more means may be used in combination, or any of the means may be used repeatedly.

  As a suitable example of the base material used in the method disclosed herein, a base material having a self-assembled film on the surface can be mentioned. Such a substrate can be excellent in surface uniformity. A substrate having a self-assembled monolayer (hereinafter sometimes referred to as “SAM”) on the surface is further preferred. For example, by using a compound having a structure in which a nonpolar group and at least one alkoxy group or halogen are bonded to silicon (Si), titanium (Ti), tantalum (Ta), or the like as a monomer, hydrophobic self-bonding is performed on the substrate surface. An organized membrane (preferably SAM) can be formed. The nonpolar group may be, for example, a hydrocarbon group (typically an alkyl group) having about 4 to 20 carbon atoms (preferably about 8 to 20 carbon atoms). The hydrocarbon group may be a nonpolar group in which part or all of the hydrogen atoms constituting the hydrocarbon group are substituted with halogen (for example, fluorine). In addition, known monomers known as those capable of forming a self-assembled film can be used without particular limitation.

The method disclosed herein is performed using a substrate having a surface that is patterned so that the affinity for the first solvent differs between the predetermined region and its surroundings (eg, the degree of hydrophobicity is different). can do. The patterned substrate can be produced, for example, as follows. That is, a hydrophobic film (preferably SAM) is formed on the substrate surface using a monomer having a photosensitive (photodegradable) hydrophobic group. Next, the hydrophobic group is decomposed by irradiating light (for example, ultraviolet light) to a portion corresponding to the predetermined region. Thereby, the hydrophobic film of the part corresponding to the predetermined region is changed to hydrophilic. In this way, a substrate having a surface patterned so that the hydrophilicity of the predetermined region is higher than the periphery of the region is obtained. Such a substrate can be preferably used, for example, in an embodiment using a hydrophilic first solvent (water, methanol, etc.).
In the above example, the light corresponding to the predetermined area is irradiated with light (positive type), but the area complementary to the predetermined area may be irradiated with light (negative type). In this case, a substrate having a surface patterned so that the hydrophilicity of the predetermined region is lower than the periphery of the region is obtained. Such a substrate can be preferably used, for example, in an embodiment using a hydrophobic first solvent (hexane, decalin, etc.).

  Examples of the monomer having a photodegradable hydrophobic group include octadecyltrichlorosilane (OTS), heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane (HFDTS), phenyltrichlorosilane, and trimethoxysilylethyl. A compound such as pyridine can be preferably used. These monomers are also suitable as monomers for forming SAM on the surface of the substrate. In a SAM formed using OTS (hereinafter also referred to as “OTS-SAM”), a silanol group is generated by photolysis of a hydrophobic octadecyl group. In addition, in a SAM formed using HFDTS (hereinafter also referred to as “HFDTS-SAM”), a silanol group is generated by the decomposition of a hydrophobic fluorodecyl group. Although not particularly limited, these hydrophobic groups can be appropriately photodegraded, for example, by irradiation with ultraviolet rays (UV).

In one preferred embodiment of the method disclosed herein, a particle dispersion is applied to the surface of the substrate, and then the substrate having the dispersion is placed in a second solvent. The method for applying the particle dispersion to the substrate surface is not particularly limited. For example, a method of supplying (dropping) the particle dispersion onto the surface of the substrate using a supply pipe such as a dropper, a method of immersing (dipping) the substrate in the particle dispersion, and a method of spraying the particle dispersion onto the surface of the substrate Etc. can be adopted as appropriate.
The method for disposing the base material having the particle dispersion in the second solvent is not particularly limited. Similarly to the case where the particle dispersion is applied to the substrate surface, a method of supplying (dropping) the second solvent from above the substrate having the particle dispersion using a supply pipe such as a dropper, a group having the particle dispersion A method of sinking the material in the second solvent, a method of spraying the second solvent from above the substrate having the particle dispersion, and the like can be appropriately employed. It is preferable to use a larger amount of the second solvent than the particle dispersion on the substrate so that the particle dispersion on the substrate can be covered with the second solvent. A method in which the substrate having the particle dispersion is submerged in the second solvent is particularly preferable.

  In another preferred embodiment, the substrate is first placed in the second solvent, and then the particle dispersion is applied to the surface of the substrate in the second solvent. For example, the tip of a dropper is brought close to the surface of the substrate in the second solvent, and the particle dispersion is supplied from the tip to the substrate surface. Further, for example, when the specific gravity of the particle dispersion (first solvent) is clearly larger than the specific gravity of the second solvent, the dispersion may be supplied from a position slightly away above the substrate surface. When the relatively heavy particle dispersion sinks in the second solvent until it reaches the substrate surface, the particle dispersion is applied to the substrate surface.

According to any of the above-described embodiments, it is possible to realize a state in which the particle dispersion is disposed on the surface of the substrate disposed in the second solvent. From this state, the first solvent contained in the dispersion is diffused into the second solvent, so that particles in the dispersion are densely accumulated to form a particle aggregate. In this diffusion step, a large amount of the second solvent is used to such an extent that the first solvent can be sufficiently diffused (dissolved). It is preferable to use a larger amount of the second solvent than at least the particle dispersion disposed on the substrate surface. Usually, it is preferable to keep the substrate substantially horizontal in the second solvent during the diffusion step. As a result, a higher quality particle aggregate can be formed.
The ultrasonic treatment may be performed in a state where the particle dispersion is disposed in the second solvent. The particle dispersion can be refined by the ultrasonic treatment to produce a particle aggregate having a smaller size. Such ultrasonic treatment can be applied regardless of whether or not a substrate is used.

  In an embodiment using a patterned base material, it is preferable that the diffusion proceeds while the particle dispersion is preferentially (preferably selectively) arranged in a predetermined region of the base material. As a result, a particle aggregate can be formed preferentially (preferably selectively) in the predetermined region. By using the substrate thus patterned as a template, a particle aggregate can be formed on the surface of the substrate in a self-organizing manner.

  In order to better control the formation position and / or formation range (two-dimensional pattern) of the particle aggregate, it is desirable to realize a state in which the particle dispersion is arranged as accurately as possible in a predetermined region of the substrate. In order to realize such a state, for example, it is preferable to increase a difference in affinity (such as a difference in the degree of hydrophobicity) of the predetermined region and its surroundings with respect to the first solvent. In consideration of the area of the predetermined region and the three-dimensional shape (mold) of the particle dispersion in the second solvent, it is preferable to dispose an appropriate amount of the particle dispersion on the substrate surface. It is also effective to appropriately move the part of the particle dispersion that protrudes from the predetermined region to the predetermined region by gently shaking the substrate to which the particle dispersion is applied.

  In order to adjust the amount of the particle dispersion disposed on the substrate surface, a part of the particle dispersion once applied to the substrate surface may be removed from the substrate surface as necessary. For example, excess particle dispersion can be removed by performing operations such as tilting or shaking the substrate, or rotating the substrate (applying centrifugal force). These techniques may be performed with the substrate placed in the second solvent.

  The invention disclosed herein can be carried out using a substrate having a predetermined region of any two-dimensional shape (that is, a region having higher affinity for the first solvent than the surroundings) on the surface. By using a substrate having a surface patterned in this way, a particle aggregate having a two-dimensional shape corresponding to the two-dimensional shape of the predetermined region can be suitably produced. In other words, the patterned surface can be suitably used as a template for producing a particle assembly having a predetermined two-dimensional shape. The method of the present invention can be applied to various geometric two-dimensional shapes such as a disk shape, polygonal shape, linear shape (bar shape), arc shape, or any other two-dimensional shape (for example, characters, symbols, etc.). It is suitable as a method for producing a particle aggregate having a shape of Moreover, it is suitable as a method for producing a particle aggregate material (substrate) in which such a two-dimensional particle aggregate is disposed on the surface of a substrate.

  Further, the invention disclosed herein uses a base material having a plurality of predetermined regions (that is, regions having higher affinity for the first solvent than the surroundings) constituting an arbitrary one-dimensional array or two-dimensional array on the surface. Can be implemented. By using a base material having a surface patterned in this way, a particle aggregate having an arrangement corresponding to each predetermined region can be suitably produced. In other words, the patterned surface can be preferably used as a template for producing (preferably, producing in a self-organizing manner) a particle assembly constituting a predetermined arrangement. The method of the present invention can be preferably applied to both the production of a plurality of regularly arranged particle aggregates and the production of irregularly arranged particle aggregates. In addition to particle aggregate materials in which a plurality of particle aggregates are arranged in one direction (one-dimensional arrangement) on the substrate surface, the production of particle aggregate materials in which two or more directions are arranged (two-dimensional arrangement) Can also be applied.

  The three-dimensional shape of the particle aggregate is imparted on the substrate, for example, the affinity between the base material and the first solvent (particle dispersion) in the region where the particle aggregate is formed and / or the surrounding region. It can be adjusted by the amount of the particle dispersion, the combination of the first solvent and the second solvent (for example, the relationship of specific gravity of both solvents), the production conditions, and the like. For example, when producing a particle aggregate having a shape close to a sphere on the surface of the substrate, it is preferable to apply the dispersion to the surface of the substrate having a low affinity for the particle dispersion. That is, when a hydrophilic solvent is used as the first solvent, the particle dispersion is applied to the hydrophobic surface of the substrate. Further, as the second solvent, it is preferable to select a solvent having a specific gravity which is approximately the same as or slightly higher than that of the first solvent. In this case, the particle dispersion applied to the surface of the substrate forms droplets having a high contact angle (preferably about 90 ° or more) with respect to the surface in the second solvent. By diffusing the first solvent contained in the droplets into the second solvent, a particle aggregate having a shape close to a sphere can be easily produced.

  In addition, by dispersing the particle dispersion in a second solvent having the same specific gravity as that of the dispersion, a substantially spherical droplet made of the particle dispersion is disposed (floating) in the second solvent. Can be realized. Then, by diffusing the first solvent contained in the particle dispersion into the second solvent, a particle aggregate having a shape close to a sphere can be obtained. By using particles having a specific gravity comparable to the specific gravity of the first solvent, fluctuations in the specific gravity of the particle dispersion accompanying the diffusion of the first solvent can be suppressed. As a result, higher quality particle aggregates can be produced.

  By carrying out the above production method using substantially monodispersed spherical particles having an average particle diameter (average diameter) d of 10 μm or less, for example, a particle aggregate as in the following aspect 1 or aspect 2 Can be manufactured.

<Aspect 1: Spherical particle assembly>
A particle aggregate (for example, a spherical particle aggregate having a radius of about 5 to 50 μm) having a spherical outer shape having a radius of 5 to 10 times the average diameter d of the spherical particles, the in-plane five-coordinate configuration described above particles (P ₅₎ and the plane 6 coordination of the particles (P ₆₎ and the plane 7 coordination of particles (P ₇₎ plane 5 coordination with respect to the total number of the particles (P ₅₎ and the surface A particle aggregate in which the ratio of the total number of 7-coordinated particles (P ₇ ) in the range of about 10 to 30% can be manufactured. In a more preferred embodiment, a particle aggregate having the ratio in the range of approximately 13 to 20% can be produced. Typically, such a particle aggregate is obtained in a state of being disposed on the surface of the substrate. The particle assembly may be shaped to form a nearly perfect sphere. In addition, a part of the sphere may have a flat shape (for example, a portion in contact with the substrate surface) (a dome shape). It is preferable that the particle aggregate has a shape closer to a sphere than at least a hemisphere (in other words, a shape in which at least the center of the sphere is located inside the aggregate). According to the method of the present invention, a spherical particle aggregate having an angle between the cut portion and the center of the sphere of 240 ° or more (more preferably 300 ° or more) can be produced on the substrate surface.

  Here, the ideal structure of a monolayer particle assembly composed of substantially monodispersed spherical particles densely arranged in a plane is that the individual particles constituting the assembly are within the same plane. Is a repetitive structure of a close-packed triangular lattice surrounded by the other 6 particles (a state in which one particle is in contact with other 6 particles in the same plane, that is, an in-plane close-packed packed structure). . On the other hand, in an ideal structure of a particle aggregate in which such particles are accumulated in a “spherical shape”, the spherical surface (spherical surface) of the aggregate cannot be covered only by repeating the closest packed triangular lattice. In the case of a spherical particle aggregate, a structure in which one particle is surrounded by other five particles in a plane (5 in-plane coordination, that is, in the same plane) is based on a close-packed triangular lattice. And / or a structure in which one particle is surrounded by other seven particles in the plane (in-plane seven-coordinate, ie, other in the same plane) It is possible to cover the spherical surface ideally (that is, densely) by introducing a state in contact with seven particles. In other words, in a typical structure of a particle assembly in which monodispersed spherical particles are densely packed in a spherical shape, in-plane five-coordinate particles and / or in-plane seven-coordinates are formed on the spherical surface of the aggregate. Of particles.

As described above, the particle aggregate disclosed herein has a ratio (number ratio) of particles having an in-plane five-coordinate structure or an in-plane seven-coordinate structure out of spherical surface constituent particles of about 10 to 30% ( The particle aggregate is preferably in the range of about 13 to 20%. The proportion of particles having an in-plane five-coordinate structure or an in-plane seven-coordinate structure among spherical constituent particles can be determined, for example, as follows.
First, the number of P ₅ , P ₆ and P _{7 on} the sphere surface of the spherical particle aggregate is, for example, an image (SEM image) obtained by observing the sphere surface of the aggregate with a scanning electron microscope (SEM). ). More specifically, for example, the number of particles P ₅ having an in-plane five-coordinate structure (n _p5 ) and the particles having an in-plane six-coordinate structure in an arbitrary region of the sphere surface appearing in the SEM image. The number of P ₆ (n _p6 ) and the number of particles P ₇ having an in-plane seven-coordinate structure (n _p7 ) are counted. Then, from the number of each particle, the in-plane 5-coordinate structure or in-plane 7-coordinate occupying the spherical surface constituent particles of the aggregate is obtained by the formula: (n _P5 + n _P7 ) / (n _P5 + n _P6 + n _P7 ); The proportion of particles having a coordinate structure can be determined.

The region to be counted for the number of P ₅ , P ₆ and P ₇ may be substantially the entire sphere surface of the particle aggregate, or may be a partial region. Usually, it is convenient to count the numbers of P ₅ , P ₆ and P ₇ for a part of the surface of the sphere (for example, a region within the circle when a virtual circle is drawn on the sphere surface). It is preferable. In a typical embodiment of the particle assembly disclosed herein, the proportion of particles having an in-plane five-coordinate structure or an in-plane seven-coordinate structure among spherical constituent particles contained in the partial region {(n _P5 + n _P7 ) / (n _P5 + n _P6 + n _P7 )} is the ratio of particles having an in-plane five-coordinate structure or in-plane seven-coordinate structure on the entire spherical surface of the particle aggregate {(N _P5 + N _P7 ) / (N _P5 + N _P6 + N _P7 )} can be employed (at least as an approximation of the ratio). That is, instead of the above relational expression: 10% <{(N _P5 + N _P7 ) / (N _P5 + N _P6 + N _P7 )} <30%; the following relational expression: 10% <{(n _P5 + n _P7 ) / (N _P5 + n _P6 + n _P7 )} <30% can be used. Percentage of particles having an in-plane five-coordinate structure or an in-plane seven-coordinate structure in the entire sphere surface of the particle aggregate by counting the number of P ₅ , P ₆ and P ₇ for a part of the sphere surface Is more appropriately approximated by a continuous region corresponding to approximately 3% or more (for example, approximately 3 to 30%) of the total surface area (4πr ² ) when the aggregate is assumed to be a sphere having a radius r. It is preferable to count the number of P ₅ , P ₆ and P ₇ for (typically a region surrounded by one circle). In other words, when the total surface area is S1 and the area of the area to be counted is S2, the area to be counted is set so that S2 / S1 is about 3% (0.03) or more. preferable. It is more preferable to set so that S2 / S1 is about 5% or more (for example, about 5 to 20%).

Using a two-dimensional SEM image obtained by observing the particle aggregate from one direction (for example, a direction perpendicular to the substrate surface when the particle aggregate is formed on the substrate surface), P ₅ , P ₆ and When counting the number of P ₇ , it is preferable that a region surrounded by a concentric circle and a circle constituting the outer shape (contour) of the particle aggregate in the SEM image is a counting target. Thereby, the ratio of the particle | grains which take the in-plane 5 coordination structure or the in-plane 7 coordination structure which occupies for the spherical surface constituent particle | grains of the particle | grain assembly can be grasped | ascertained more correctly. In this case, for example, the region (count target region) surrounded by the concentric circles with respect to the total surface area when the aggregate is assumed to be a sphere having a radius r is approximately 5 to 15% ( That is, it is appropriate to set the radius of the concentric circles so that S2 / S1 is about 5 to 15%.

Assuming that the particle aggregate is an almost perfect sphere, the numbers of P ₅ , P ₆ and P ₇ in the total surface area of the aggregate are N _P5 , N _P6 and N _P7 , respectively. When the number of P ₅ , P ₆ and P ₇ in any surface region (count target region) S2 is n _P5 , n _P6 and n _P7 , the value of N _P5 is expressed by the formula: N _P5 = n _P5 × ( S1 / S2); Similarly, the value of N _{P6 formula: N P6 = n P6 × (} S1 / S2); the value of N _{P7 formula: N P7 = n P7 × (} S1 / S2); can be calculated by.

<Aspect 2: Particle aggregates accumulated in a predetermined two-dimensional pattern on the substrate surface>
A particle aggregate in which the spherical particles are accumulated on the surface of the substrate in a predetermined two-dimensional pattern, which satisfies at least one of the following (A) and (B) can be produced.
(A) The pattern has a portion where the virtual contour line is linear, and the standard deviation S of the distance from the center of the particles constituting the outer edge of the aggregate to the virtual contour line in the linear portion. Is equal to or less than 1 × 10 ⁻² μm; and (B) the pattern has an arcuate portion having a virtual contour line, and the center of the particle constituting the outer edge of the aggregate is formed in the arcuate portion. The standard deviation S of the distance to the virtual contour line is 5 × 10 ⁻¹ μm or less.
Here, the “particles constituting the outer edge of the aggregate” typically correspond to particles that are continuously arranged on the outermost side of the particle aggregate.

With regard to (A) above, the “part where the virtual contour line is linear” means a plurality (at least 20 or more) constituting the outer edge of the aggregate when the particle aggregate is viewed from a direction perpendicular to the substrate surface. (Preferably 30 or more) refers to a portion where the position of the center of the particle is well approximated by a linear line. Based on the distance from the center of each particle to the approximate straight line (that is, the virtual contour line), the standard deviation S can be obtained by a conventional method. In one preferable aspect of the particle assembly disclosed herein, at least a part of the virtual contour line is a linear contour line extending in the <1 −1 0> direction in the hexagonal lattice structure (fcc). . The contour line extending in such a direction (in other words, the outer edge of the particle aggregate in the linear portion) can show a particularly clear contour (see FIG. 7E).
Regarding (B), the “virtual contour is a circular arc portion” means a plurality (at least 10) constituting the outer edge of the aggregate when the particle aggregate is viewed from a direction perpendicular to the substrate surface. The center of the particle (more than or equal to 30 or more, preferably 30 or more) refers to a portion that is well approximated by an arc. Based on the distance from the center of each particle to the virtual contour (arc), the standard deviation S can be obtained by a conventional method (for example, as in Example 4 described later).

Hereinafter, the present invention will be described in more detail with reference to examples.
<Example 1: Formation of particle aggregate by water / hexane two-component system>
The surface of the silicon substrate was treated with octadecyltrichlorosilane (OTS) to produce a silicon substrate having a hydrophobic surface. That is, an OTS solution containing OTS at a concentration of 1 vol% in dry toluene was prepared, and a silicon substrate was immersed in this solution for 5 minutes. Next, the silicon substrate was heated to 120 ° C. for 5 minutes. In this way, a silicon substrate having a self-assembled monolayer (OTS-SAM) derived from octadecyltrichlorosilane on the surface was obtained. The contact angle of water on the OTS-treated surface of the silicon substrate was about 105 °, and it was confirmed that hydrophobic OTS-SAM was formed.

As a raw material particle for producing a particle aggregate, a trade name “HI-PRECICA UF N3N” available from Ube Nitto Kasei Co., Ltd. was used. This material was SiO ₂ particles having a substantially spherical particle shape and had a very sharp (substantially monodisperse) particle size distribution. The average diameter d of the SiO ₂ particles constituting the material is about 1.13 μm, and the particle size accuracy (CV value) is 3.57% (that is, standard deviation = 0.0357 × 1.13 μm = 0.0403 μm). The specific gravity was 1.8 ± 0.1 g / cm ³ . A particle dispersion was prepared by dispersing 0.2 mg of the SiO ₂ particles in 20 μL of water (first solvent). Then, as shown in FIG. 1A, particle dispersion in which SiO ₂ particles 22 are dispersed in water 24 on the hydrophobic surface 12 (that is, on the OTS-SAM) of the silicon substrate 10 surface-treated as described above. Liquid 20 was added dropwise. The dropped particle dispersion formed several droplets on the hydrophobic surface 12.

Next, the silicon substrate 10 having droplets of the particle dispersion 20 was immersed in 20 mL of hexane (second solvent) 30 (FIG. 1B). When ultrasonic treatment for 1 minute was performed in this state, a relatively large droplet of the particle dispersion 20 was separated into a plurality of small droplets on the hydrophobic surface 12 (FIG. 1C). As the water 24 contained in these droplets (particle dispersion) 20 gradually diffused into the surrounding hexane 30, each droplet 20 gradually shrunk. On the other hand, the SiO ₂ particles 22 included in each droplet 20 were left on the substrate 10. After immersion for 12 hours, particle aggregates 40 of various sizes having a generally spherical outer shape were observed on the hydrophobic surface 12 of the substrate 10 (FIG. 1D). In this example, the specific gravity of water (first solvent) as a dispersion medium of the particle dispersion is larger than the specific gravity of hexane (0.7).

Some particle aggregates obtained in this example were observed with a scanning electron microscope (SEM). The obtained SEM images are shown in FIGS. Among these, (A) to (G) are images obtained by observing each integrated body from almost directly above (that is, a direction perpendicular to the substrate surface), and (H) and (I) are images observed obliquely from above. is there. 2 (A) to 2 (D) show aggregates composed of 3, 5, 6, and 8 particles, respectively. These aggregates composed of 3, 5, 6, and 8 particles were regularly accumulated to form a triangle, tetrahedron, octahedron, and decahedron, respectively. FIGS. 2E to 2I show a spherical particle aggregate including a larger number of particles.
As described above, according to this example, a spherical particle dispersion is dispersed in water, and the dispersion is dispersed (dissolved) in the surrounding hexane by disposing (dispersing) the water in the hexane. A particle aggregate in which particles were densely accumulated was formed. The particle dispersion applied to the hydrophobic surface (OTS-SAM) forms droplets having a high contact angle in hexane, thereby forming a particle aggregate having a shape close to a sphere (for example, a diameter of about 3 to 10 μm). A spherical particle aggregate) was obtained. In addition, particle aggregates of various sizes were obtained by applying ultrasonic treatment after applying the particle dispersion to the substrate.

<Example 2: Formation of particle aggregate by methanol / decalin two-component system>
A particle dispersion was prepared by dispersing 0.2 mg of the same SiO ₂ particles as used in Example 1 in 20 μL of methanol (first solvent). This particle dispersion was dropped on a silicon substrate having a hydrophobic surface (OTS-SAM) in the same manner as in Example 1.
A silicon substrate having droplets of the dispersion was immersed in 20 mL of decalin (decahydronaphthalene; second solvent). The particle dispersion droplets on the substrate in decalin had a diameter in the range of approximately 100-300 μm. In addition, unlike Example 1, the ultrasonic treatment after immersion was not performed in this example. Further, since the specific gravity (0.79) of methanol, which is the dispersion medium of the particle dispersion, is smaller than the specific gravity (0.88) of decalin, the immersion operation in decalin is carried out from the hydrophobic surface of the substrate. It was carried out quietly so as not to float away. In such a state of being immersed in decalin, the methanol contained in the particle dispersion gradually diffused into decalin leaving SiO ₂ particles, whereby the droplets on the substrate gradually contracted. After immersion for 12 hours, a spherical particle aggregate larger than that of Example 1 (for example, a spherical particle aggregate having a diameter of approximately 57 μm) was formed on the hydrophobic surface of the substrate.

  An SEM image of the obtained particle assembly is shown in FIG. The diameter of the particle aggregate is about 57 μm. As shown in the figure, some linear disclinations (line defects) were observed on the surface of the integrated body. FIG. 3 (B) displays a mesh connecting the center of each sphere surface constituent particle and the center of the adjacent sphere surface constituent particle for a part of the sphere surface, overlaid on the same SEM image as FIG. 3 (A). Is. From this mesh shape, it can be seen that the particle accumulation structure constituting the spherical surface of the spherical accumulation body is based on a close-packed triangular lattice. In addition, the disclination observed on the sphere surface consists of particles surrounded by five sphere surface constituent particles (in-plane five-coordinate particles; indicated by thin dots in the figure) and seven sphere surfaces. It can be seen that it is composed of particles surrounded by constituent particles (in-plane seven-coordinate particles; indicated by dark dots in the figure).

Note that the radius of the spherical particle aggregate is r, the diameter of the monodisperse particles (in this case, SiO ₂ particles) constituting the aggregate is d, the total surface area of the sphere having the radius r is S1, In a two-dimensional photograph (for example, SEM image), the area of the region surrounded by the concentric circle (ie, the radius of the count target region on the SEM image) that is concentric with the circle constituting the outer shape (contour) of the aggregate is S2, and the two-dimensional of the concentric circle When the radius in the photograph is r ₁ , the theoretical minimum number N of line defects in the total surface area S1 and the theoretical minimum number n of line defects in the area S2 of the partial region can be obtained by the following equations. (See FIGS. 8A to 8C.) Here, in the particle aggregate shown in FIG. 3B, r = 28.5 μm and d = 1.13 μm. Further, the concentric circles shown in the figure have a radius r ₁ = 17.5 μm.

That is, when the particle aggregate shown in FIGS. 3A and 3B is an almost perfect sphere, the theoretical minimum number N of line defects existing in the total surface area S1 is determined to be about 22. Further, in FIG. 3B, the area S2 of the region surrounded by a circle (radius r ₁ = 17.5 μm of the circle) is a sphere having a radius (r = about 28.5 μm) equivalent to this particle aggregate. Corresponds to 10.5% of the total surface area (ie, S2 / S1 = 10.5%), the theoretical minimum number n of line defects existing in the area S2 is determined to be about 2.3.

In addition, in-plane 5-coordinate in a region surrounded by a circle in FIG. 3B (as described above, a region corresponding to 10.5% of the total surface area of a sphere having the same radius as this aggregate). The total number (n _P5 + n _P7 ) of particles and in-plane 7-coordinated particles is 149. This corresponds to about 13.8% of the total number (n _P5 + n _P6 + n _P7 ) of the global surface constituent particles contained in the circle. That is, in the particle aggregate shown in FIGS. 3A and 3B, (n _P5 + n _P7 ) / (n _P5 + n _P6 + n _P7 ) = 13.8%.

  The upper part of the spherical particle aggregate obtained in this example was removed, and the state of particle accumulation inside this aggregate was observed. As a result, it was confirmed that the integrated body had an integrated structure densely packed inside.

<Example 3: Two-dimensional arrangement of particle aggregate by methanol / decalin two-liquid system>
The surface of the silicon substrate was treated with heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane (HFDTS) to produce a silicon substrate having a hydrophobic surface. That is, an HFDTS solution containing HFDTS at a concentration of 1 vol% in dry toluene was prepared, and a silicon substrate was immersed in this solution for 5 minutes. Next, the silicon substrate was heated to 120 ° C. for 5 minutes. Thus, a silicon substrate having on its surface a self-assembled monolayer (HFDTS-SAM) derived from heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane was obtained. The contact angle of water on the HFDTS treated surface of the silicon substrate was about 112 °, and it was confirmed that hydrophobic HFDTS-SAM was formed.

  Next, as shown in FIG. 4A, the hydrophobic surface 112 of the silicon substrate 110 (that is, on the HFDTS-SAM) was irradiated with ultraviolet rays (UV) for two hours through a photomask. As the photomask, a photomask having a shape in which irradiation windows having a diameter of about 100 μm are regularly arranged at intervals of about 50 μm is used. The region (predetermined region) irradiated with UV in the hydrophobic surface 112 changed to hydrophilicity due to the generation of silanol groups. The contact angle of water in the region was 5 ° or less. On the other hand, the region not irradiated with UV was kept hydrophobic. As a result, several hydrophilic regions 114 were formed in the hydrophobic region 112. These hydrophilic regions 114 were regularly arranged in the hydrophobic region 112 corresponding to the arrangement of the irradiation windows of the photomask used. The HFDTS-SAM (patterned HFDTS-SAM) 115 patterned in this manner was used as a template for producing micropatterning (microarrays) of particle aggregates. In addition, the silicon substrate used for the present Example was 10 mm x 10 mm square shape.

The same SiO ₂ particles as those used in Example 1 were dispersed in methanol (first solvent) to prepare a particle dispersion containing the SiO ₂ particles at a rate of 1 g / L. Then, as shown in FIG. 4B, 10 μL of the particle dispersion 120 was applied onto the patterned HFDTS-SAM 115 formed on the surface of the silicon substrate 110. Next, the silicon substrate 110 provided with the particle dispersion 120 was immersed in 50 mL of decalin (second solvent) 130. In this state, a gentle vibration was applied to the silicon substrate 110. As described above, since the specific gravity of methanol is smaller than the specific gravity of decalin, excess dispersion liquid floated away from the substrate 110 by the application of the vibration. In addition, this vibration promoted the movement of the dispersion 120 on the hydrophobic region 112 of the patterned HFDTS-SAM 115 onto the hydrophilic region 114. As a result, as shown in FIG. 4C, the droplets of the particle dispersion 120 are selectively positioned on the hydrophilic region 114. That is, a micro pattern of droplets of the particle dispersion 120 was configured corresponding to the arrangement of the hydrophilic regions 114. These droplets (particle dispersion) 120 had a shape close to a sphere due to the interfacial interaction between methanol 124, decalin 130, and the substrate surface, and the buoyancy of methanol 124 in decalin 130.

After 12 hours of immersion, as shown in FIG. 4D, spherical (dome-shaped) particle aggregates 140 made of SiO ₂ particles 122 are formed in each hydrophilic region (silanol region) 114, respectively. It was. In other words, corresponding to the arrangement of the hydrophilic regions 114, the particle accumulation in which the spherical particle aggregates 140 are arranged with good regularity two-dimensionally (in the vertical direction and the horizontal direction of the substrate surface). Body patterning (array) 150 was obtained. According to another aspect, a particle assembly material 160 having a particle assembly patterning 150 on the surface of the substrate 110 was obtained.
FIG. 5A shows an SEM image obtained by observing the particle aggregate patterning (arrangement) almost directly from above, and FIG. 5B shows an SEM image observed from obliquely above. The distance between the centers of the particle aggregates was approximately the same as the distance between the irradiation windows of the photomask used for forming the hydrophilic region.
FIG. 5C shows an SEM image obtained by observing one of the particle aggregates constituting the patterning from almost directly above, and FIG. 5D shows an SEM image obtained by observing the other one from obliquely above. The average diameter of the particle aggregate constituting the particle aggregate patterning was about 18 μm. As apparent from FIGS. 5C and 5D, the spherical surfaces of these particle aggregates were formed by closely packed SiO ₂ particles. Further, when the upper part of the particle aggregate was removed in the same manner as in Example 2, it was confirmed that the aggregate had an accumulation structure tightly packed to the inside.
Thus, according to this example, using a substrate having a surface (patterned HFDTS-SAM) patterned by a difference in affinity for methanol (first solvent), spherical particle accumulation on the substrate surface is performed. A body dot array (dotted array) could be formed in a self-organizing manner. As a result, a particle aggregate material in which the particle aggregates are regularly arranged on the surface of the substrate (here, the silicon substrate) was obtained.

<Example 4: Formation of particle aggregate by methanol / hexane two-component system>
In the same manner as in Example 1, a silicon substrate having a self-assembled monolayer (OTS-SAM) derived from octadecyltrichlorosilane on the surface was obtained. The OTS-SAM (hydrophobic surface) on the surface of the substrate was irradiated with UV for 10 minutes through a photomask having an irradiation window having a predetermined shape and arrangement. In the region irradiated with UV, the hydrophobic octadecyl group was changed to a hydrophilic silanol group. Thereby, the pattern of the hydrophilic region (silanol region) was formed in the hydrophobic OTS-SAM (octadecyl region). By using a plurality of types of photomasks having different shapes and arrangements of irradiation windows, silicon substrates having hydrophilic regions having shapes and arrangements corresponding to the photomasks in the hydrophobic regions were prepared. The silicon substrate having the OTS-SAM patterned in this way (patterned OTS-SAM) was used as a template for producing a particle assembly integrated in a predetermined pattern.

A particle dispersion was prepared by dispersing SiO ₂ particles having a diameter of 1.13 μm (trade name “HI-PRECICA UF” available from Ube Nitto Kasei Co., Ltd.) in methanol (first solvent). The particle size accuracy (CV value) of the SiO ₂ particles used here is 2.0% or less (that is, standard deviation = 0.02 × 1.13 = 0.0226 μm or less). As shown in FIG. 6A, this particle dispersion 220 was applied onto the patterned OTS-SAM 215 of the silicon substrate 210. As described above, the patterned OTS-SAM 215 has a hydrophilic region (silanol region) 214 having a predetermined shape and arrangement in the hydrophobic region (octadecyl region) 212. Since the hydrophobic octadecyl region 212 has a property of repelling the dispersion 220, the dispersion 220 was mainly present on the hydrophilic silanol region 214.
Next, as shown in FIG. 6B, the silicon substrate 210 to which the dispersion liquid 220 was applied was immersed in hexane 230 (specific gravity 0.7), and the substrate 210 was shaken to remove excess dispersion liquid ( Shaken off the board). The particle dispersion 220 remaining on the patterned OTS-SAM 215 in hexane 230 was repelled well in the octadecyl region 212 and was selectively present on the silanol region 214.

  The contact angle on the OTS-SAM (on the octadecyl region) of the particle dispersion using methanol as a dispersion medium was 51.6 ° in air, but increased to 129.5 ° in hexane. did. This indicates that the tendency of the dispersion to be selectively present on the hydrophilic region is further enhanced in hexane compared to air. Therefore, in hexane, a particle dispersion having a shape that corresponds well to the shape of the pattern can be more easily formed (molded) on the patterned substrate.

From the state shown in FIG. 6B, the mold of the dispersion 220 gradually contracted as the methanol 224 contained in the particle dispersion 220 gradually diffused into the hexane 230 leaving the SiO ₂ particles 222. In this process, as schematically shown in FIGS. 6C and 6D, the SiO ₂ particles 222 left in the mold are attracted to each other by the meniscus force and densely gathered. As a result, as shown in FIG. 6E, a particle aggregate 240 composed of dense SiO ₂ particles 222 was selectively formed on the hydrophilic silanol region 214. In this way, a particle aggregate patterning (array) 250 composed of a plurality of particle aggregates 240 selectively formed on the silanol region 214 was obtained. According to another aspect, a particle assembly material 260 having a particle assembly patterning 250 on the surface of the substrate 210 was obtained.

SEM images of the particle assembly thus obtained are shown in FIGS. The composition (particle concentration) of the particle dispersion used for the production of these particle aggregates is as follows.
FIGS. 7A and 7B: SiO ₂ particles 0.2 mg / methanol 20 μL,
FIGS. 7C and 7D: SiO ₂ particles 0.02 mg / methanol 20 μL,
FIGS. 7E to 7G: SiO ₂ particles 0.002 mg / methanol 20 μL.

FIG. 7A shows the particle accumulation obtained by using a silicon substrate having a surface patterned so that rod-shaped hydrophilic regions (silanol regions) are regularly arranged in hydrophobic regions (octadecyl regions). It is a SEM image of a body. As shown in the figure, a particle aggregate patterning (array) in which the particle aggregates are regularly arranged was formed. The width of each rod-shaped particle aggregate is approximately 40 μm, and the interval between adjacent rod-shaped particle aggregates is approximately 40 μm. As described above, according to this example, a plurality of particle aggregates were arranged on the surface of the base material (here, the silicon substrate) with high regularity two-dimensionally (in two directions, the vertical direction and the horizontal direction). A particle assembly material was obtained.
FIG. 7B is an enlarged SEM image of a part of FIG. As shown in the figure, at the peripheral edge of the particle assembly, the particles were accumulated on the substrate so as to form a single particle layer (monolayer). The central part of the aggregate was thicker than the peripheral part, and it was confirmed that particles were stacked in ten layers at the thickest part (constituting a ten-particle layer).

  FIG. 7C is an SEM image of a particle aggregate obtained using a silicon substrate having a surface in which a hydrophilic region having the shape of Arabic numeral “2” is patterned in a hydrophobic region. As shown in the figure, the feature edge of the obtained particle aggregate had a high degree of clarity. As described above, according to this example, a particle assembly pattern having a clear outline was produced on a silicon substrate. In other words, a particle assembly material was obtained in which a particle assembly pattern having such a clear outline was disposed on the surface of a substrate (here, a silicon substrate).

  FIG. 7D is an SEM image of a particle assembly obtained using a silicon substrate having a surface in which a circular hydrophilic region is patterned in a hydrophobic region. As shown in the figure, a particle aggregate accumulated in a circular pattern was obtained. The central part (core part) of the circular aggregate was a two-particle layer and constituted a close-packed hexagonal lattice (that is, an fcc {111} array). Further, the outer edge portion (outer shell portion) of the circular aggregate was a single particle layer and constituted a hexagonal lattice (fcc {111}). The particles in the boundary part (inner shell part) of these two flat parts constituted a nested cubic lattice (that is, fcc {100}). The lattice constant of the cubic lattice in the inner shell portion gradually increased according to the distance from the central portion, and a gentle slope was formed between the one-particle layer portion and the two-particle layer portion.

FIGS. 7E to 7G are SEM images of one-particle layer (monolayer) particle aggregates accumulated in a predetermined two-dimensional pattern. The particles constituting these patterns had an fcc {111} array (hexagonal lattice structure) which is a close-packed structure. As is apparent from the figure, these particle aggregates were very few defects (ie, had a near ideal accumulation structure). For example, the leftmost particle among the particles constituting the contour (edge) of the particle assembly shown in FIG. 7E is the origin of the xy coordinates, and the individual centers of the other contour-constituting particles are xy. The standard deviation (S) of the distance to the virtual contour obtained by plotting on the coordinates was 8.75 × 10 ⁻³ . The calculation of the standard deviation was performed on 35 particles arranged in sequence from the leftmost particle in FIG. 7E (that is, the number of particles n = 35). According to this example, a particle aggregate pattern having a very clear outline was obtained in this way.
Note that the direction in which the outline of the particle aggregate shown in FIG. 7E extends (substantially in the horizontal direction in the figure) corresponds to the <1 −1 0> direction in fcc. In addition, the direction in which the outline of the particle aggregate shown in FIG. 7F extends (substantially in the vertical direction in the figure) corresponds to the <1/2 1/2 -1> direction in fcc.

Further, for all (112) particles arranged on the outer edge of the particle aggregate shown in FIG. 7G, the virtual contour lines of the particles constituting the aggregate are as follows. The standard deviation of distance was calculated.
Of the n (here, n = 112) particles forming the outer periphery of the single particle layer circular pattern, the coordinates of the center of the i-th particle are x _i and y _i (μm), and the coordinates of the center of the circle are Assuming x _o and y _o (μm), the distance from the center of the circle of the i-th particle is given by the following equation.

The average value r (upper bar) of this distance is given by the following equation.

1. The unbiased variance U of this distance is given by
Here, the unbiased variance represents the dispersion of the observed values and is also an estimated value of the dispersion in the population from which the observed values were obtained (referred to as “unbiased estimated value of the population variance”).
When n is smaller than the “total number of target particles” as a population, the population variance is estimated using unbiased variance. On the other hand, when n is equal to the “total number of target particles” that is the population, the standard deviation is calculated using the variance V.

From this unbiased variance, the standard deviation S is given by

2. The variance V of the distance from the center of the particle circle is given by:
Here, since all the particles arranged on the outer edge of the particle aggregate shown in FIG. 7G are calculated as target particles (n = 112), the standard deviation is calculated using the variance.
When n is the same number as the “total number of target particles” as the population, the standard deviation is calculated using the variance V (the variance is used when calculating the dispersion of the obtained data itself).

From this variance, the standard deviation S is given by:

In the case of the particle aggregate shown in FIG. 7G, the standard deviation S is as follows.

However, the error from the calculation result using unbiased variance is so small that it can be ignored.

  In addition, although this invention is not specifically limited, the mechanism in which a high quality particle aggregate is formed by this invention can be demonstrated as follows, for example. That is, when the first solvent (particle dispersion medium) contained in the droplet (mold) of the particle dispersion diffuses into the surrounding second solvent, the particles contained in the dispersion try to stay in the droplet. . As the diffusion of the first solvent proceeds and the droplets gradually shrink, the area where the particles can exist gradually becomes smaller and eventually the particles come into contact with each other. As water diffusion further progresses, it is believed that the particles are rearranged by interfacial strain and a close-packed aggregate is formed.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

(A)-(D) is explanatory drawing which shows typically the particle | grain assembly manufacturing process of Example 1. FIG. (A)-(I) are the SEM images of the particle | grain assembly obtained by Example 1, respectively. (A) is the SEM image of the particle | grain assembly obtained by Example 2, (B) is explanatory drawing which showed the accumulation state of the particle | grains superimposed on this SEM image. (A)-(D) is explanatory drawing which shows typically the particle | grain assembly manufacturing process of Example 3. FIG. (A) and (B) are SEM images of the particle aggregate patterning obtained in Example 3, and (C) and (D) are SEM images of the particle aggregate constituting the patterning. (A)-(E) is explanatory drawing which shows typically the particle | grain assembly manufacturing process of Example 4. FIG. (A)-(G) are the SEM images of the particle | grain assembly obtained by Example 4. FIG. (A)-(C) is a figure for demonstrating how to obtain | require S2 / S1 and the minimum number of a line defect.

Explanation of symbols

10, 110, 210: Silicon substrate (base material)
12: Hydrophobic surface (substrate surface)
112, 212: hydrophobic region (substrate surface)
114, 214: hydrophilic region (substrate surface, predetermined region)
115 Patterned HFDTS-SAM (substrate surface)
215 Patterned OTS-SAM (base material surface)
20, 120, 220: Particle dispersion 22, 112, 212: SiO ₂ particles (particles, spherical particles)
24: Water (first solvent)
124, 224: Methanol (first solvent)
30,230: Hexane (second solvent)
130 Decalin (second solvent)
40,140,240 Particle Aggregate 150,250 Particle Aggregate Patterning 160,260 Particle Aggregate Material

Claims (9)

A particle aggregate in which substantially monodispersed spherical particles are densely aggregated, under the following conditions:
The outer shape of the aggregate is spherical;
The average diameter d of the particles is 10 μm or less;
The ratio (r / d) of the radius r of the aggregate itself to the average diameter d is in the range of 5-50; and
The individual particles constituting the sphere surface of the aggregate are composed of particles (P ₅ ) in which the particles are surrounded by five spherical surface constituent particles and those particles are surrounded by six spherical surface constituent particles. And the number of particles corresponding to P ₅ (N _P5 ) and the number of particles (P ₆ ) and the particles surrounded by seven spherical surface constituting particles (P ₇ ) The relationship between the number of particles corresponding to P ₆ (N _P6 ) and the number of particles corresponding to P ₇ (N _P7 ) is _expressed by the following formula:
10% <{(N _P5 + N _P7 ) / (N _P5 + N _P6 + N _P7 )} <30%;
Satisfy;
A particle assembly comprising: A particle aggregate in which substantially monodispersed spherical particles are densely aggregated, under the following conditions:
The particles are accumulated in a predetermined two-dimensional pattern on the surface of the substrate;
The average diameter d of the particles is 10 μm or less; and
The aggregate is composed of the following (A) and (B):
(A) The pattern has a portion where the virtual contour line is linear, and the standard deviation S of the distance from the center of the particles constituting the outer edge of the aggregate to the virtual contour line in the linear portion. Is equal to or less than 1 × 10 ⁻² μm; and (B) the pattern has an arcuate portion having a virtual contour line, and the center of the particle constituting the outer edge of the aggregate is formed in the arcuate portion. The standard deviation S of the distance to the virtual contour is 5 × 10 ⁻¹ μm or less;
Satisfy at least one of the following;
A particle assembly comprising: A method for producing a particle assembly in which particles are densely integrated, comprising the following steps:
Preparing a particle dispersion in which the particles are dispersed in a first solvent;
Placing the dispersion in a second solvent capable of phase separation with the first solvent; and
Diffusing the first solvent contained in the dispersion in the second solvent while maintaining the particles contained in the dispersion substantially in the arranged state;
A method for producing a particle assembly comprising: A method for producing a particle aggregate formed by dense accumulation of particles on a substrate surface, comprising the following steps:
Preparing a particle dispersion in which the particles are dispersed in a first solvent;
Applying the dispersion to the surface of the substrate;
Disposing the substrate in a second solvent capable of phase separation with the first solvent;
A step of diffusing the first solvent contained in the dispersion into the second solvent while leaving the particles contained in the dispersion on the substrate surface in the second solvent in the second solvent;
A method for producing a particle assembly comprising:   The method according to claim 4, wherein the substrate surface is patterned such that a predetermined region has a higher affinity for the first solvent than the periphery of the region.   The method according to any one of claims 3 to 5, wherein substantially monodispersed spherical particles are used as the particles. A method for producing a particle assembly material in which a particle assembly formed by dense integration of particles is disposed on the surface of a substrate, comprising the following steps:
Preparing a particle dispersion in which the particles are dispersed in a first solvent;
Applying the dispersion to the surface of the substrate;
Disposing the substrate in a second solvent capable of phase separation with the first solvent; and
A step of diffusing the first solvent contained in the dispersion into the second solvent while leaving the particles contained in the dispersion on the substrate surface in the second solvent in the second solvent;
A method for producing a particle assembly material comprising:   The substrate surface is patterned so that affinity for the first solvent in a predetermined region is higher than that around the region, and the particle aggregate is disposed corresponding to the predetermined region. Item 8. The method according to Item 7.   The method according to claim 8, wherein two or more predetermined regions are formed on the surface of the base material so as to form a predetermined pattern, and the particle aggregate is arranged corresponding to the pattern.