JP6232859B2 - Method for producing metal nanoparticle dispersion - Google Patents

Description

  The present invention relates to a method for producing a metal nanoparticle dispersion.

  It is known that metal particles (metal nanoparticles) having a particle size of about several nanometers to several tens of nanometers exhibit various physical and chemical characteristics different from those in the case of bulk. For example, the melting point of metal nanoparticles is lower than in the bulk case. For this reason, metal nanoparticles are used in conductive inks, conductive pastes, fillers, and the like as materials that can achieve high conductivity and stability while having a low sintering temperature.

  In addition, attempts have been made to apply the optical properties of metal nanoparticles to the fields of molecular diagnosis and optical devices. It is known that metal nanoparticles have optical properties corresponding to their particle sizes. For example, in the case of silver particles, it is known that the plasmon absorption peak shifts to the longer wavelength side and becomes broader as the particle size increases.

As a method for producing metal nanoparticles, a method of reducing a metal salt using a reducing agent in a solvent is known (Patent Documents 1, 2, etc.). When producing metal nanoparticles using such a method, it is necessary to have equipment corresponding to the oxidation-reduction reaction, time is required for the oxidation-reduction reaction, and the reducing agent remains in the obtained metal nanoparticle dispersion. There are various problems such as variations in the particle diameter of the metal nanoparticles.
Patent Document 3 discloses a method of adjusting the particle size of the gold colloid by estimating the particle size of the gold colloid obtained by the oxidation-reduction reaction from the optical properties of the solution of the gold colloid.

Japanese Patent No. 5140035 Japanese Patent No. 4108350 JP 2007-23384 A

  This invention is made | formed in view of the said situation, and is providing the manufacturing method of the novel metal nanoparticle dispersion liquid which does not use a reducing agent.

In the method for producing a metal nanoparticle dispersion according to the present invention, a plurality of microprotrusions are closely arranged, an average distance between adjacent microprotrusions is 500 nm or less, and a member having a microprotrusion structure on the surface The process of preparing
Preparing a protective agent solution containing a protective agent and at least one selected from water and an organic solvent;
Forming and supporting metal nanoparticles by attaching metal atoms to the surface of the microprojection structure using a vapor deposition method; and
A step of bringing the surface of the microprojection structure carried by the metal nanoparticles into contact with the protective agent solution and transferring the metal nanoparticles to the protective agent solution,
The vapor deposition method is characterized in that the thickness of a vapor deposition film formed by metal atoms adhering to a flat surface is adjusted to 40 nm or less.

  The manufacturing method of the metal nanoparticle dispersion liquid of this invention can be used suitably for the metal nanoparticle which consists of gold | metal | money, silver, copper, palladium, or platinum.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the novel metal nanoparticle dispersion liquid which does not use a reducing agent can be provided.

FIG. 1 is a schematic process diagram showing an example of a method for producing a metal nanoparticle dispersion according to the present invention. FIG. 2 is a schematic diagram illustrating an example of a Delaunay diagram. FIG. 3 is a schematic cross-sectional view showing an example of a microprojection structure. FIG. 4 is a schematic plan view showing an example of the arrangement of the microprojections forming the microprojection structure. FIG. 5 is a schematic view showing an example of a method for forming a microprojection structure.

Hereinafter, the manufacturing method of the metal nanoparticle dispersion according to the present invention will be described in detail.
In the present specification, the terms “plate”, “sheet”, and “film” are not distinguished from each other only based on the difference in names.
In addition, “film surface (plate surface, sheet surface)” means a target film-like member (plate-like) when the target film-like (plate-like, sheet-like) member is viewed as a whole and globally. It refers to a surface that coincides with the planar direction of the member (sheet-like member).
Furthermore, as used in this specification, the shape and geometric conditions and the degree thereof are specified. For example, terms such as “parallel”, “orthogonal”, “identical”, length and angle values, etc. Without being bound by meaning, it should be interpreted including the extent to which similar functions can be expected.

In the method for producing a metal nanoparticle dispersion according to the present invention, a plurality of microprotrusions are closely arranged, an average distance between adjacent microprotrusions is 500 nm or less, and a member having a microprotrusion structure on the surface The process of preparing
Preparing a protective agent solution containing a protective agent and at least one selected from water and an organic solvent;
Forming and supporting metal nanoparticles by attaching metal atoms to the surface of the microprojection structure using a vapor deposition method; and
A step of bringing the surface of the microprojection structure carried by the metal nanoparticles into contact with the protective agent solution and transferring the metal nanoparticles to the protective agent solution,
The vapor deposition method is characterized in that the thickness of a vapor deposition film formed by metal atoms adhering to a flat surface is adjusted to 40 nm or less.

  The manufacturing method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic process diagram showing an example of a method for producing a metal nanoparticle dispersion according to the present invention. In the example of FIG. 1, as shown in FIG. 1A, a plurality of microprojections 2 are closely arranged, and the average distance d between the adjacent microprojections is 500 nm or less. The member 10 having the surface is prepared. Moreover, as shown to FIG. 1 (B), the protective agent solution 4 containing a protective agent and 1 or more types selected from water and an organic solvent is prepared. Next, as shown in FIG. 1C, metal nanoparticles 3 are formed by attaching metal atoms to the surface of the microprojection structure 1 by vapor deposition, and the surface of the microprojection structure 1 is formed. Carry. Next, as shown in FIG. 1D, the surface of the microprojection structure 1 carried by the metal nanoparticles 3 is brought into contact with the protective agent solution 4 to transfer the metal nanoparticles 3 to the protective agent solution 4 ( 5). In this way, a metal nanoparticle dispersion 20 is obtained as shown in FIG.

As a result of intensive studies, the present inventors have found that when metal atoms are attached to the surface of the specific microprojection structure using a vapor deposition method adjusted to the specific conditions, metal nanoparticles are not a bulk vapor deposition film. The knowledge that it is formed was obtained. Although the action of forming metal nanoparticles by depositing metal atoms in a specific amount on the surface of the microprojection structure is unclear, in the microprojection structure having the specific shape, metal atoms are It is presumed that when deposited, it is in an environment that can exist stably as a single particle.
Furthermore, it is clear that the particle size distribution of the metal nanoparticles obtained by the above specific method tends to be smaller than that of metal nanoparticles obtained by a conventionally known oxidation-reduction method or the like. became. Therefore, according to the production method of the present invention, there is an advantage that it is easy to adjust to a desired particle size.
The vapor deposition film formed on the flat surface in the vapor deposition method is usually uniform in thickness, and the amount of metal atoms deposited per unit area is substantially constant in the plane. Similarly, even on the surface of the microprojection structure, the amount of metal atoms adhering per unit area is almost constant in the plane, so that the metal nanoparticles formed on the surface of the microprojection structure have a uniform particle size. It is estimated that the particle size distribution of the metal nanoparticles tends to be small. Moreover, in the manufacturing method of this invention, as the conditions of the said vapor deposition method, it adjusts beforehand so that the thickness of the vapor deposition film formed with the metal atom adhering on a flat surface may be 40 nm or less. Therefore, metal nanoparticles formed on the surface of the microprojection structure are difficult to aggregate. In the production method of the present invention, the particle size and particle size distribution of the metal nanoparticles can be appropriately changed by changing the average distance and deviation between the microprotrusions and the thickness of the deposited film formed on the flat surface within a range of 40 nm or less. It can be adjusted appropriately.
When the metal nanoparticles formed on the surface of such a microprojection structure are brought into contact with water or an organic solvent and separated from the microprojection structure, the metal nanoparticles are transferred to water or an organic solvent. In the present invention, by using the above specific protective agent solution, the protective agent adheres to the surface of the metal nanoparticles in water or an organic solvent, so that the metal nanoparticle dispersion liquid is obtained by dispersing without aggregation. be able to.
Thus, according to the production method of the present invention, a metal nanoparticle dispersion can be easily obtained without using a reducing agent. Moreover, according to the manufacturing method of this invention, there exists a merit that it is easy to prepare the metal nanoparticle dispersion liquid containing the metal nanoparticle with a small particle size distribution adjusted to the desired particle size.

<Step of preparing a member having a microprojection structure on the surface>
A member 10 (hereinafter, simply referred to as “member 10”) having a microprojection structure on the surface used in the manufacturing method of the present invention has a plurality of microprojections 2 arranged in close contact with each other and between the adjacent microprojections. The surface of the microprojection structure 1 has an average distance d of 500 nm or less. Metal nanoparticles can be formed by attaching metal atoms to the surface of the microprojection structure 1 by vapor deposition.

(Member having a microprojection structure on the surface)
In the present invention, the member 10 having the microprojection structure on the surface only needs to have at least one surface of the specific microprojection structure, and the other portions can have any shape, but are easy to manufacture. In addition, from the point that it is easy to separate the metal nanoparticles, a group of microprotrusions in which a plurality of microprotrusions made of a resin composition or a cured product thereof are closely arranged on one side of a sheet-like substrate It is preferable that it is a member which has the microprotrusion structure provided with.

  In the microprojection structure 1, a plurality of microprojections 2 are closely arranged. Each microprotrusion constituting the microprotrusion structure is formed so as to be planted on the base material, and the shape thereof is not particularly limited, but it is assumed that the microprojection is cut by a horizontal plane perpendicular to the depth direction of the microprotrusion. The cross-sectional area occupancy rate of the material part forming the microprojections in the horizontal cross section when it is gradually increased from the top of the microprojection toward the deepest portion, that is, each microprojection is tapered. Those having a structure are preferred. Specific examples of the shape of such minute protrusions include those having a vertical cross-sectional shape such as semicircular, semielliptical, triangular, parabolic, bell-shaped. The plurality of microprotrusions may have the same shape or different shapes. Moreover, it is preferable that the top of the fine protrusion has a curved surface.

In the present invention, the microprotrusions constituting the microprotrusion structure have a distance d between adjacent microprotrusions (hereinafter referred to as “distance between adjacent protrusions d”) so that metal nanoparticles are formed. It arrange | positions closely so that average _dAVG may be 500 nm or less. The adjacent minute protrusions related to the distance d between the adjacent protrusions are so-called adjacent minute protrusions, and are protrusions that are in contact with the skirt portions of the minute protrusions that are base portions on the base material side. In the member having the microprojection structure used in the present invention on the surface, when the microprojections are closely arranged, a line segment is created so as to sequentially follow the valley portions between the microprojections. A mesh-like pattern formed by connecting a large number of polygonal regions surrounding each minute protrusion is produced. The adjacent minute protrusions related to the distance d between the adjacent protrusions are protrusions that share a part of the line segments constituting the mesh pattern.
The average distance d _AVG between adjacent adjacent protrusions of the minute protrusions may be selected as appropriate. Among these, the average distance d _AVG between adjacent protrusions is preferably 50 to 300 nm, and particularly preferably 70 to 180 nm. If the average distance d _AVG between adjacent protrusions is equal to or greater than the above lower limit, the distance between the formed metal nanoparticles is secured and aggregation is unlikely to occur. On the other hand, when the average distance d _AVG between adjacent protrusions is equal to or less than the above upper limit value, it is difficult to form a deposited film and metal nanoparticles are easily formed.
The height H of the microprotrusions (H in FIG. 1) may be set as appropriate. Among them, the average value _{H AVG} height is preferably from 50～350Nm, and more preferably 100 to 250 nm.

In the present invention, the distance d between adjacent protrusions and the height H of the minute protrusions are measured by the following method.
(1) First, an in-plane arrangement of projections (planar shape of the projection arrangement) is detected using an atomic force microscope (AFM) or a scanning electron microscope (SEM).

  (2) Subsequently, a maximum point of the height of each protrusion (hereinafter simply referred to as a maximum point) is detected from the obtained in-plane arrangement. There are various methods for obtaining the maximum point, such as a method of sequentially comparing the planar view shape and the enlarged photograph of the corresponding cross-sectional shape to obtain the maximum point, and a method of obtaining the maximum point by image processing of the plan view enlarged photo. Can be applied.

  (3) Next, a Delaunay diagram with the detected maximum point as a generating point is created. FIG. 2 is a schematic plan view showing an example of a Delaunay diagram. As shown in the example of FIG. 2, the Delaunay diagram is defined such that, when Voronoi division is performed using each local maximum point 21 as a generating point, generating points adjacent to each other in Voronoi regions are defined as adjacent generating points. It is a net-like figure composed of a triangular aggregate obtained by connecting each other with a line segment 22. Each triangle is called a Delaunay triangle, and a side of each triangle (a line segment connecting adjacent generating points) is called a Delaunay line.

  (4) Next, from the enlarged photograph of the frequency distribution of the line length of each Delaunay line, that is, the distance between adjacent maximum points (distance between adjacent protrusions) in a plan view, about 5 to 20 of the above-mentioned minute adjacent to each other Select a microprojection that does not have a structure, sample the value of the distance between adjacent projections, and clearly deviate from the numerical range obtained by sampling (typically the average distance between adjacent projections obtained by sampling) The frequency distribution is detected by excluding data whose value is 1/2 or less of the value.

(5) The frequency distribution of the distance d between adjacent protrusions thus determined is regarded as a normal distribution, and the average value d _AVG and the standard deviation σ _d are determined. In the present invention, the maximum value d _max of the distance d between adjacent protrusions is defined as d _max = d _AVG + 2σ _d and is calculated.

A similar technique is applied to define the height of the protrusion. In this case, a relative height difference of each local maximum point position from a specific reference position is acquired from the local maximum point obtained by the above (2), and is histogrammed. The average value H _AVG of the projection height and the standard deviation σ _H are obtained from the frequency distribution based on this histogram.
The microprojection of the present invention may have a microstructure in which a recess is present at the top of the projection or a microstructure in which the top is split into a plurality of peaks. In the case where a microprojection having a microscopic structure in which a concave portion exists at the top of such a projection or a microstructure in which the top is divided into a plurality of peaks is included, one microprojection has a plurality of vertices. Thus, the plurality of data are mixed in the histogram of the protrusion height H for one protrusion. Therefore, in this case, the frequency distribution is obtained by adopting the vertex having the highest height from among the plurality of vertices belonging to the same microprotrusion as the protuberance.

  The reference position for measuring the height of the microprojections is the base position of the projection, that is, the valley bottom (minimum point of height) between the adjacent microprojections is used as the reference for the height 0. However, when the height of the valley bottom itself varies depending on the location, for example, when the envelope surface connecting the valley bottoms between the microprojections has a concavo-convex shape with a large period compared to the distance between adjacent projections of the microprojections ( (1) First, an area sufficient to converge the average value of the height of each valley bottom measured from the surface opposite to the surface 31 of the microprojection structure 30 of the microprojection structure 30. Calculate in (2) Next, a plane having the average height and parallel to the surface opposite to the microprojection surface 31 of the microprojection structure 30 is considered as a reference plane. (3) Then, the height of each microprotrusion from the reference surface is calculated by setting the reference surface to a height of 0 again.

  Further, in order to ensure good smoothness of the microprojection structure 30, the height difference (h in FIG. 3) of the concavo-convex surface 33 undulated with the period D is preferably 10 nm or less, and 1 nm to 5 nm. It is more preferable to be within the range. In addition, the height difference of the uneven surface formed by the uneven surface 33 can be obtained by measuring the height difference of the position of the valley bottom portion of the minute protrusion 32 separated by, for example, 500 nm or more. The position of the valley bottom portion of the microprojection 32 can be obtained by observing the microprojection structure 30 using a TEM photograph or SEM photograph of a vertical section cut in the thickness direction.

When the microprotrusions in the first microprotrusion structure have the same height H and the microprotrusions are regularly arranged at a constant period, the standard deviation σ _{d of the} distance d between adjacent protrusions becomes zero. Since it coincides with the period p of the microprojection arrangement, d _AVG = p.
On the other hand, when the protrusions are irregularly arranged, the average distance between adjacent protrusions obtained as described above may be 500 nm or less.
When it is desired to reduce the particle size distribution of the metal nanoparticles, the standard deviation σ _{d of the} distance between adjacent protrusions may be reduced, and σ _d = 0, that is, the minute protrusions are regularly arranged at a constant period. preferable.

The aspect ratio of the fine protrusions (average protrusion height H _AVG / average adjacent protrusion interval d _AVG ) is not particularly limited as long as the effects of the present invention are not impaired, but is preferably 0.8 to 2.5, and 0.8 to 2.1 is more preferable.

In addition, the microprojections forming the surface of the microprojection structure are periodically arranged in a hexagonal lattice shape, a quasi-hexagonal lattice shape, a tetragonal lattice shape, or a quasi-tetragonal lattice shape from the viewpoint of good formation of metal nanoparticles. It is preferable that
Here, the hexagonal lattice refers to a regular hexagonal lattice, and the quasi-hexagonal lattice refers to a distorted regular hexagonal lattice unlike a regular hexagonal lattice. Further, the tetragonal lattice refers to a regular tetragonal lattice, and the quasi-tetragonal lattice refers to a distorted regular tetragonal lattice unlike the regular tetragonal lattice.
To be arranged periodically in a hexagonal lattice means to be periodically arranged in a regular hexagonal lattice pattern, and to be arranged periodically in a quasi-hexagonal lattice, for example, an arrangement of microprojections Examples include those periodically arranged in a hexagonal lattice pattern stretched in the direction and distorted. In addition, the arrangement | sequence of a microprotrusion may meander not only in linear form. As shown in FIG. 4, between the adjacent three rows of linear arrays (T1 to T3), by arranging the microprojections 34 so that the centers of the microprojections 34 are located at the points a1 to a7, The microprojections 34 are periodically arranged in a hexagonal lattice pattern or a quasi-hexagonal lattice pattern.
In the present invention, the microprojections forming the surface of the microprojection structure preferably have a high filling ratio of the microprojections from the viewpoint of good formation of metal nanoparticles, and the microprojections are closely arranged. Is more preferable. Among these, it is more preferable that the minute projections are periodically arranged in a hexagonal close-packed lattice shape.

  The thickness of the first microprojection structure (T in FIG. 1) may be adjusted as appropriate, but is preferably 3 μm to 30 μm, and more preferably 5 μm to 10 μm.

In the present invention, from the viewpoint that metal nanoparticles are easily formed, the static contact angle of pure water on the surface of the microprojection structure is preferably 90 ° to 160 ° by the θ / 2 method. More preferably, it is ˜150 °.
In the present invention, the static contact angle is defined as the straight line connecting the left and right end points and the apex of the dropped droplet to the surface of the solid after 1.0 s of pure water is dropped on the surface of the object to be measured. The contact angle is measured according to the θ / 2 method for calculating the contact angle from the angle. As the measuring device, for example, a contact angle meter DM 500 manufactured by Kyowa Interface Science Co., Ltd. can be used.

(Manufacturing method of member having microprojection structure on surface)
The method for producing a member having a microprojection structure on the surface is not particularly limited as long as the method can form the above-described microprojection structure.
As a specific example of a method for producing a member having a microprojection structure provided with a microprojection group in which a plurality of microprojections made of a cured resin composition is closely arranged on one surface of a substrate, A resin composition for forming microprojection structures is applied onto a substrate to form a coating film, and the uneven shape of the original plate for forming microprojection structures having a desired uneven shape is applied to the coating film of the resin composition. Examples thereof include a method of forming a microprojection structure by curing the resin composition after shaping, and peeling the original plate for forming the microprojection structure.
The concave / convex shape of the original plate for forming a microprojection structure is a shape in which a large number of micropores are densely formed and corresponds to the shape of a group of microprojections provided in the microprojection structure.
Moreover, the method of shaping the concave / convex shape of the original plate for forming a microprojection structure into a resin composition and curing the resin composition can be appropriately selected according to the type of the resin composition.

(1) Base material The base material may be selected as appropriate and is not particularly limited. Examples of the material used for the base material include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, olefin resins such as polyethylene and polymethylpentene, acrylic resins, polyurethane resins, polyethersulfone and polycarbonate, Resins such as polysulfone, polyether, polyetherketone, acrylonitrile, methacrylonitrile, cycloolefin polymer, cycloolefin copolymer, glass such as soda glass, potassium glass, lead glass, ceramics such as PLZT, inorganic such as quartz and fluorite Examples include materials, metals, paper, wood, and composite materials thereof.
Further, the substrate may be any of those supplied in the form of a roll, those that do not bend enough to be wound, but that are curved by applying a load, and those that do not bend completely. You can choose.

The structure of the base material used in the present invention is not limited to a structure composed of a single layer, and may have a structure in which a plurality of layers are laminated. When it has the structure by which the several layer was laminated | stacked, the layer of the same composition may be laminated | stacked, and the several layer which has a different composition may be laminated | stacked.
In addition, when the microprojection structure to be described later is formed on a microprojection layer made of a material different from the substrate, the surface performance of the substrate such as adhesion between layers, coating suitability, and surface smoothness is improved. From the above, an intermediate layer may be formed on the substrate.

(2) Resin composition The resin composition for forming the microprojection structure includes at least a resin and, if necessary, other components such as a polymerization initiator. The resin used in the resin composition is not particularly limited. For example, ionizing radiation curable resins such as acrylate-based, epoxy-based, and polyester-based resins, and thermosetting such as acrylate-based, urethane-based, epoxy-based, and polysiloxane-based resins. Various materials such as thermoplastic resins such as curable resins, acrylate-based, polyester-based, polycarbonate-based, polyethylene-based, and polypropylene-based resins, and molding resins in various cured forms can be used. The ionizing radiation means electromagnetic waves or charged particles having energy that can be cured by polymerizing molecules. For example, all ultraviolet rays (UV, UV-B, UV-C), visible rays, gamma rays, X Examples thereof include an electron beam and an electron beam.

  As the resin, an ionizing radiation curable resin is preferable from the viewpoint of excellent moldability and mechanical strength of fine protrusions. The ionizing radiation curable resin is a mixture of a monomer having radically polymerizable and / or cationically polymerizable bonds in the molecule, a polymer having a low polymerization degree, and a reactive polymer, depending on the polymerization initiator. It is to be cured. In addition, you may contain a non-reactive polymer.

  The resin composition for forming the microprojection structure further comprises a polymerization initiator, a release agent, a photosensitizer, an antioxidant, a polymerization inhibitor, a crosslinking agent, an infrared absorber, an antistatic agent, if necessary. A viscosity modifier, an adhesion improver, etc. can also be contained.

(3) Microprojection structure forming original plate The microprojection structure forming original plate is not particularly limited as long as it does not deform and wear when repeatedly used, and may be made of metal. Although it may be made of resin, metal is usually preferably used because it is excellent in deformation resistance and wear resistance.
The surface having the concavo-convex shape of the original plate for forming a microprojection structure is not particularly limited, but is preferably made of aluminum from the viewpoint of being easily oxidized and easily processed by anodization.
Specifically, the original plate for forming the microprojection structure has high purity by sputtering or the like directly on the surface of a metal base material such as stainless steel, copper, or aluminum, or through various intermediate layers. An aluminum layer is provided, and the aluminum layer is formed with an uneven shape. Prior to providing the aluminum layer, the surface of the base material may be made into a super mirror surface by an electrolytic composite polishing method in which electrolytic elution action and abrasion action by abrasive grains are combined.
Examples of a method for forming a concavo-convex shape on the original plate for forming a microprojection structure include, for example, an anodic oxidation step of forming a plurality of micropores on the surface of the aluminum layer by an anodic oxidation method, and etching the aluminum layer. A first etching step for forming a tapered shape in the opening of the microhole, and a second for enlarging the hole diameter of the microhole by etching the aluminum layer at an etching rate higher than the etching rate of the first etching step. It can be formed by sequentially repeating the etching process.
When forming an uneven shape on the original plate for forming a microprojection structure, the purity (impurity amount), crystal grain size, anodizing treatment and / or etching treatment conditions of the aluminum layer are appropriately adjusted to obtain a desired shape. It can be a shape. In the anodic oxidation treatment, more specifically, the micropores can be produced to the desired depth and shape by managing the liquid temperature, the applied voltage, the time for the anodic oxidation, and the like.

Moreover, examples of the shape of the original plate for forming a microprojection structure include a flat plate shape and a roll shape, and are not particularly limited, but a roll shape is preferable from the viewpoint of improving productivity. In the present invention, it is preferable to use a roll-shaped mold (hereinafter sometimes referred to as “roll mold”) as the original plate for forming the microprojection structure.
As the roll mold, for example, as described above, a cylindrical metal material is used as a base material, and the aluminum layer provided on the peripheral side surface of the base material directly or through various intermediate layers, as described above. In other words, the concavo-convex shape is produced by repeating the anodizing treatment and the etching treatment.

  In FIG. 5, a member having a microprojection structure on the surface is manufactured by using an ultraviolet curable resin composition as a resin composition for forming the microprojection structure and using a roll mold as an original plate for forming the microprojection structure. An example of how to do this is shown. In this manufacturing method, first, in the resin supply step, an uncured and liquid ultraviolet curable resin composition that constitutes the receiving layer 46 of the microprojection structure is applied to the substrate 45 in the form of a belt-like film by the die 41. . In addition, about application | coating of an ultraviolet curable resin composition, not only the case by the die | dye 41 but various methods are applicable. Subsequently, the pressing roller 43 presses and presses the base material 45 against the peripheral side surface of the roll die 42 which is a shaping die, thereby bringing the uncured receiving layer 46 into close contact with the base material 45 and the roll. The fine concavo-convex recesses formed on the peripheral side surface of the mold 42 are sufficiently filled with the ultraviolet curable resin composition constituting the receiving layer 46. In this state, the ultraviolet curable resin composition is cured by irradiation with ultraviolet rays, whereby the microprojection structure 47 of the substrate 45 is formed. Subsequently, the substrate 45 is peeled off from the roll die 42 via the peeling roller 44 together with the hardened microprojection structure 47. If necessary, an adhesive layer or the like is laminated on the substrate 45 and then cut into a desired size. Thereby, a microprojection structure in which microprojections having a desired shape are formed is formed.

When the standard deviation σ _{d of} the microprojection distance d and the standard deviation σH of the microprojection height _H are increased, the micropore spacing of the microprojection structure forming original plate produced in the anodizing process This can be achieved by making the difference. A microprotrusion having a recess at the top of the protrusion is formed by a microhole having a recess having a shape corresponding to the top, and such a microhole is formed by a microhole formed in close proximity. It is considered that they are integrally formed by etching.
In addition, when there is a variation in height within a predetermined range for each microprojection of the microprojection structure, the variation in the height of each microprojection is the depth of the microhole formed in the original plate for forming the microprojection structure. It can be said that such a variation in the depth of the micropores is caused by a variation in the anodizing process. In this way, a mixture of a relatively high top microprojection and a plurality of relatively low peripheral microprojections can be realized by increasing the variation in anodizing treatment.

  Further, in the above-described embodiment, the case where the forming method of the microprojection structure is produced on the film-shaped base material by the shaping process using the roll mold is described. Depending on the shape of the material, for example, when forming a microprojection structure by processing a flat plate or a single wafer using a mold for shaping with a specific curved surface shape, It can be appropriately changed according to the shape of the material.

<Step of preparing a protective agent solution>
In this step, a protective agent solution containing a protective agent and at least one dispersion medium selected from water and an organic solvent is prepared.
The protective agent is used to suppress aggregation of metal nanoparticles and improve dispersibility, and can be appropriately selected from conventionally known materials according to the dispersion medium. Examples of the protective agent include organic compounds having a polar group. Examples of the polar group include a carboxy group, a phospho group, a phosphino group, a sulfo group, a sulfino group, a hydroxy group, a thiol group, and an amino group. Is mentioned.

  Specific examples of the protective agent include citric acid, adipic acid, caproic acid, dodecanoic acid, stearyl acid, oleic acid, linoleic acid, linolenic acid; phenylphosphonic acid, diethylphosphonic acid, pentamethylphosphonic acid, diphenylphosphonic acid; pentamethyl Phosphinic acid, diphenylphosphinic acid, phenylmethylphosphinic acid, diamylphosphinic acid, dihexylphosphinic acid, diheptylphosphine, triphenylphosphine, trioctylphosphine, diphenylphosphinoethane, trioctylphosphine oxide; n-tetradecylsulfuric acid; Dodecyl sulfate, decyl sulfate, n-nonyl sulfate, n-octyl sulfate, dodecylbenzenesulfonic acid; dodecanesulfinic acid, benzenesulfinic acid; dodecanediol, hexadecanediol; hexane All, octanethiol, decanethiol, dodecanethiol, hexadecanethiol, trimethylbenzyl mercaptan, butylbenzyl mercaptan; butylamine, trioctylamine, octylamine, octadecylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, stearylamine, Examples include distearylamine, oleylamine, and benzylamine. Further, mercaptoundecanoic acid, mercaptohexanoic acid, mercaptohexadecanoic acid, mercaptohexanol, mercaptododecanol, mercaptohexadecanol, L-glutamic acid, diphenyldithiophosphinic acid, and salts thereof can be mentioned. Further, for example, a hydrocarbon alkyne compound described in Japanese Patent No. 5177339 may be used. The protective agent is not limited to these examples.

  In the metal nanoparticle dispersion liquid, water or an organic solvent used as a dispersion medium is not particularly limited as long as it does not react with each component in the metal nanoparticle dispersion liquid and can dissolve or disperse them. Specifically, in addition to water, alcohols such as methyl alcohol, ethyl alcohol, N-propyl alcohol, and isopropyl alcohol; ether alcohols such as methoxy alcohol, ethoxy alcohol, methoxyethoxyethanol, ethoxyethoxyethanol, and propylene glycol monomethyl ether Ester systems such as ethyl acetate, butyl acetate, 3-methoxybutyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, and ethyl lactate; ketone systems such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; methoxyethyl acetate, methoxypropyl Acetate, methoxybutyl acetate, ethoxyethyl acetate, ethyl cellosolve acetate, methoxyethoxyethyl acetate Ether alcohol acetates such as propylene glycol monomethyl ether acetate, diethylene glycol monobutyl ether acetate and diethylene glycol monoethyl ether acetate; ethers such as diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether and tetrahydrofuran; N, N-dimethyl Aprotic amides such as formamide, N, N-dimethylacetamide and N-methylpyrrolidone; lactones such as γ-butyrolactone; unsaturated hydrocarbons such as benzene, toluene, xylene and naphthalene; n-heptane, n- Organic solvents such as saturated hydrocarbons such as hexane and n-octane are exemplified.

In addition, various additives may be added as long as the effects of the present invention are not impaired.
What is necessary is just to adjust suitably the content rate of the protective agent in a protective agent solution. Especially, it is preferable that it is 1-50 mass parts with respect to 100 mass parts of protective agent solution whole quantity, and it is more preferable that it is 5-20 mass parts.

<Process for forming metal nanoparticles>
This step is a step of forming and supporting metal nanoparticles by attaching metal atoms to the surface of the microprojection structure using a vapor deposition method.
In the present invention, metal nanoparticles can be formed by attaching a predetermined amount of metal atoms to the surface of the microprojection structure by vapor deposition.
The vapor deposition method in this step may be appropriately selected from conventionally known methods capable of depositing metal atoms, and examples thereof include a vacuum vapor deposition method, a physical vapor deposition method, and a chemical vapor deposition method. The method is preferably used.

The said vapor deposition method is preset so that the thickness of the vapor deposition film formed with the metal atom adhering on a flat surface may be 40 nm or less.
As a method for setting the vapor deposition method, for example, first, a vapor deposition apparatus used for the vapor deposition method is set in advance to an arbitrary condition. A member having a flat surface is used instead of a member having a microprojection structure on the surface, and the same metal as the metal nanoparticles to be manufactured is deposited on the flat surface by vapor deposition using the vapor deposition apparatus. A metal deposition film is obtained. If the thickness of the vapor deposition film is 40 nm or less, the preset conditions can be used as the vapor deposition apparatus conditions in the production method of the present invention.
By appropriately adjusting the thickness of the deposited film formed on the flat surface within a range of 40 nm or less, the particle size of the metal nanoparticles can be controlled.

In the case of the vacuum deposition method, a vacuum deposition apparatus provided with a vacuum exhaust system, an evaporation source, and a substrate holder is usually used.
As the vacuum exhaust system, a conventionally known high vacuum exhaust system may be used. For example, an oil rotary pump, a dry pump, or the like can be used as the roughing pump, and a roots pump or the like can be used as a booster pump if necessary. As the high vacuum pump, a diffusion pump, a cryopump, or the like can be used. When a diffusion pump is used, a cold trap at about −120 to −150 ° C. may be further provided.
The evaporation source has a heating source for heating and evaporating the metal. Examples of the heating source include resistance heating and electron beam heating.

For example, first, a member having the microprojection structure on the surface is placed on the substrate holder so that the surface of the microprojection structure faces the evaporation source. After the inside of the vacuum container of the vacuum evaporation apparatus is evacuated to about 10 ⁻⁵ to 10 ⁻⁶ Torr, the metal is heated so that the vapor pressure of the metal is about 1 to 10 ⁻⁶ Torr in the evaporation source, and the minute Metal atoms may be attached to the surface of the protruding structure.

In the present invention, the metal atom may be appropriately selected according to the use of the obtained metal nanoparticle dispersion, and is not particularly limited. Among these, gold, silver, copper, palladium, or platinum is preferable from the viewpoints of metal stability, easiness of vapor deposition, and the like.
The metal nanoparticles produced in the present invention usually have an average particle size smaller than the average distance between adjacent microprojections of the microprojection structure used during formation. The average particle diameter of the metal nanoparticles is preferably 10 to 100 nm, and more preferably 10 to 50 nm, from the viewpoint of being easily present between the microprotrusions.

  The average particle diameter of the metal nanoparticles can be determined by a method of directly measuring the size of the primary particles from an electron micrograph of the surface of the microprojection structure to which the metal nanoparticles are attached. Specifically, the minor axis diameter and major axis diameter of each primary particle are measured, and the average is taken as the particle diameter of the particle. Next, for each of 100 or more particles, the volume (mass) of each particle is obtained by approximating a rectangular parallelepiped having the obtained particle size, and is obtained as a volume average particle size, which is defined as the average particle size. Note that the same result can be obtained regardless of whether the electron microscope is a transmission type (TEM), a scanning type (SEM), or a scanning transmission type (STEM).

<Process of transferring metal nanoparticles to protective agent solution>
This is a step of bringing the surface of the microprojection structure supported by the metal nanoparticles into contact with the protective agent solution to transfer the metal nanoparticles to the protective agent solution.
The method for contacting the surface of the microprojection structure with the protective agent solution is not particularly limited. As shown in FIG. 1D, in addition to the method of immersing the member 10 having the microprojection structure on the surface in the protective agent solution. And a method of spraying a protective agent solution on the member and recovering the solution. In addition, in order to raise recovery efficiency, you may give a vibration etc. to the said member and protective agent solution suitably.
Since the protective agent adheres to the surface of the metal nanoparticles transferred into the protective agent solution, the metal nanoparticles do not aggregate with each other, and a good metal nanoparticle dispersion can be obtained.
In addition, the member 10 after metal nanoparticle collection | recovery can be repeatedly used for the manufacturing method of this invention.

<Application of metal nanoparticle dispersion>
Since the metal nanoparticle dispersion obtained by the production method of the present invention has metal nanoparticles having a desired particle size and a small particle size distribution, it can be suitably used for various conventionally known applications. The metal nanoparticle dispersion liquid of the present invention includes, for example, a conductive material, a material imparting a color unique to metal nanoparticles, an antibacterial material, a material imparting heat ray shielding, a material imparting antistatic properties, a fluorescent material, Used for medical materials such as catalyst materials, magnetic materials, and drug delivery systems. Moreover, you may use the metal nanoparticle dispersing agent obtained by the manufacturing method of this invention for the metal film formation use by baking.

  Hereinafter, the present invention will be specifically described with reference to examples. These descriptions do not limit the present invention.

(Production Example 1: Production of a member having a microprojection structure on the surface)
(1-1) Manufacture of original plate for forming microprojection structure After polishing a rolled aluminum plate having a purity of 99.50% so that the surface has an irregular shape with a 10-point average roughness Rz of 30 nm and a period of 1 μm In an electrolytic solution of 0.02 M oxalic acid aqueous solution, anodization was performed for 120 seconds under the conditions of a formation voltage of 40 V and 20 ° C. Next, as a first etching process, an etching process was performed for 60 seconds with the electrolytic solution after anodization. Subsequently, as the second etching treatment, a pore size treatment was performed with a 1.0 M phosphoric acid aqueous solution for 150 seconds. Furthermore, the said process was repeated and these were added and implemented 5 times in total. As a result, an anodized aluminum layer having fine irregularities formed on the aluminum substrate was formed. Finally, a fluorine-based mold release agent was applied and an excess mold release agent was washed to obtain a first master for forming a microprojection structure. In addition, the fine uneven shape formed in the aluminum layer has an average distance between adjacent micropores of 100 nm, an average depth of 200 nm, and a large number of micropores that are gradually reduced in the depth direction. It was a shape.

(1-2) Preparation of resin composition 20 parts by mass of dipentaerythritol hexaacrylate (DPHA), 70 parts by mass of Aronix M-260 (manufactured by Toagosei Co., Ltd.), 10 parts by mass of hydroxyethyl acrylate, 3 parts by mass of lucillin TPO, A resin composition was prepared by dissolving in a 1: 1 mixed solvent of methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK).

(1-3) Manufacture of a member having a microprojection structure on the surface The resin composition obtained in (1-2) above is obtained by microfabricating the original plate for microprojection structure formation obtained in (1-1). It is coated and filled so that the uneven surface is covered and the thickness of the fine uneven layer after curing is 20 μm, on which a triacetyl cellulose film (TAC) with a thickness of 80 μm as a transparent substrate (manufactured by Fuji Film Co., Ltd.) Were bonded together obliquely, and then the bonded body was pressed with a rubber roller under a load of 10 N / cm ² . After confirming that the uniform composition was applied to the entire original plate, ultraviolet rays were irradiated from the transparent substrate side with an energy of 2000 mJ / cm ² to cure the resin composition for forming a fine uneven layer. Then, it peeled from the original plate and obtained the member which has a microprotrusion structure on the surface.

(Production Example 2: Preparation of protective agent solution)
5 parts by weight of sodium citrate was added to 95 parts by weight of water to prepare a 5% aqueous sodium citrate solution, which was used as a protective agent solution.

(Example 1: Production of metal nanoparticle dispersion)
Silver nanoparticles were formed by attaching silver atoms (Ag) to the surface of the microprojection structure of the member having the microprojection structure obtained in Production Example 1 by vacuum deposition. The member having the microprojection structure carrying the silver nanoparticles on its surface is immersed in 50 mL of the protective agent solution obtained in Production Example 2, and the silver nanoparticles are transferred from the surface of the microprojection structure to the protective agent solution. A metal nanoparticle dispersion was obtained.
In addition, the vapor deposition method was preset so that the thickness of the vapor deposition film formed with the silver atom adhering on a flat surface might be set to 5 nm.

(Examples 2-3: Production of metal nanoparticle dispersion)
In Example 1, the metal nanoparticle dispersion liquid of Examples 2-3 was obtained like Example 1 except having changed the conditions of the vapor deposition method as shown in Table 1.

(Examples 4 to 6)
In Example 1, metal atoms of Examples 4 to 6 were used in the same manner as in Example 1 except that gold atoms (Au) were used instead of silver atoms, and the conditions of the vapor deposition method were changed as shown in Table 1. A dispersion was obtained.

  In addition, the conditions of the vacuum evaporation method in Table 1 are values set in advance so that the evaporation film formed by the metal atoms adhering to the flat surface has a predetermined film thickness.

[Evaluation of particle size and particle size distribution]
As a result of measuring the particle size of the metal nanoparticles by observing the surface of the microprojection structure on which the metal nanoparticles were formed, using a scanning electron microscope, in Examples 1 to 3, silver nanoparticles of around 10 nm In Examples 4 to 6, gold nanoparticles of around 30 nm were observed.

DESCRIPTION OF SYMBOLS 1 Microprotrusion structure 2 Microprotrusion 3 Metal nanoparticle 4 Protective agent solution 5 Transfer of metal nanoparticle to protective agent 10 Member having microprotrusion structure on the surface 20 Metal nanoparticle dispersion liquid 21 Maximum point 22 of microprotrusion Minute 23 Microprotrusion 30 Microprotrusion structure 31 Microprotrusion surface 32 Microprotrusion 33 Uneven surface 34 Microprotrusion 41 Die 42 Roll die 43 Press roller 44 Peeling roller 45 Base material 46 Receptive layer 47 Microprotrusion structure

Claims (4)

A step in which a plurality of microprojections are closely arranged, an average distance between adjacent microprojections is 500 nm or less, and a member having a microprojection structure on the surface is prepared;
Preparing a protective agent solution containing a protective agent and at least one selected from water and an organic solvent;
Forming and supporting metal nanoparticles by attaching metal atoms to the surface of the microprojection structure using a vapor deposition method; and
A step of bringing the surface of the microprojection structure carried by the metal nanoparticles into contact with the protective agent solution and transferring the metal nanoparticles to the protective agent solution,
The said vapor deposition method is a manufacturing method of the metal nanoparticle dispersion liquid adjusted so that the thickness of the vapor deposition film formed with the metal atom adhering on a flat surface may be 40 nm or less.   The method for producing a metal nanoparticle dispersion according to claim 1, wherein the metal nanoparticles are made of gold, silver, copper, palladium, or platinum.   The step of preparing a member having the microprojection structure on the surface includes a plurality of microprojections made of a resin composition or a cured product thereof closely arranged, and an average distance between adjacent microprojections is 500 nm or less. The method for producing a metal nanoparticle dispersion according to claim 1, wherein the method comprises preparing a member having a microprojection structure on the surface.   The above-mentioned vapor deposition method is performed in a vacuum vessel of a vacuum vapor deposition apparatus. ^-5 -10 ^-6 In a Torr vacuum state, the vapor pressure of the metal is 1-10. ^-6 The manufacturing method of the metal nanoparticle dispersion liquid of any one of Claims 1-3 which is the vapor deposition method which heat-evaporates a metal so that it may become Torr.