JP2010018447A - Surface-coated porous oxide particle and method for coating surface of porous oxide particle - Google Patents

Abstract

A surface capable of preventing binder components such as dispersants and resins from entering into open pores and maintaining the characteristics of porous oxide particles such as low refractive index and low dielectric property. Provided are a coated porous oxide particle and a surface coating method of the porous oxide particle.
The surface-coated porous oxide particles of the present invention form a reaction point 5 on the outer peripheral surface 2 of a porous oxide particle 1 made of silicon oxide or the like, and the reaction point 5 is coated with an organic polymer. The layer 6 is bonded and fixed, and the opening end of the open hole 3 is sealed by the coating layer 6, the inside of the open hole 3 is made hydrophilic, and the thickness of the coating layer 6 is 0.1 nm or more and 30 nm or less. It was.
[Selection] Figure 1

Description

  The present invention relates to a surface-coated porous oxide particle and a surface coating method of the porous oxide particle, and more specifically, a porous oxide suitably used as a low refractive index material or a low dielectric material and having open pores. Even when the particles are dispersed in a binder component such as a resin, the binder component such as a resin is prevented from entering the open pores formed in the porous oxide particle. The present invention relates to a surface-coated porous oxide particle capable of maintaining characteristics and a surface coating method of the porous oxide particle.

Conventionally, various porous oxide particles are known, and in particular, porous oxide particles having open pores with pores opened on the surface are low refractive index materials or low dielectric constants as they are. It may be used as a body material, or it may be used in a state of being dispersed in a binder component such as an organic solvent or a resin after surface treatment using a dispersant or the like to ensure dispersibility. .
For example, a porous oxide fine particle having a fine open pore of about 1 to 10 nm on the surface of a particle having a particle size of 10 to 500 nm has many pores in the particle, and thus has a low refractive index since before. It is used as a rate material, a low dielectric material, etc.

  These materials include fine particles having pores containing air having an average particle size of 5 nm to 300 nm and an average pore size of 0.01 nm to 100 nm, and a binder component containing a thermosetting resin and a silicate compound. A low refractive index composition having a nanoporous structure (Patent Document 1), having pores containing air having a particle diameter of 5 nm to 300 nm and an average pore diameter of 0.01 nm to 100 nm, and a refractive index of 1.20. A low refractive index layer (patent document 2) containing hollow silica fine particles or porous silica fine particles of ˜1.45 and an organic solvent and binder resin containing 50% or more of an aqueous organic solvent as a coating resin composition, ethylenic Containing porous silica particles having an average particle diameter of 5 to 50 nm, comprising an unsaturated group-containing fluoropolymer and a hydrolyzate of an organosilicon compound Consisting fat cured product low refractive index layer (Patent Document 3) have been proposed.

In addition, from the viewpoint of securing the bond between the particle and the binder, for the purpose of increasing the bonding force between the particle surface and the binder, the cavity has an average particle diameter of 5 to 300 nm and has pores filled with a solvent or gas inside. Antireflective film in which a low refractive index layer containing particles or composite particles having a coating layer provided on the surface of a porous particle, a nonionic surfactant, and a binder component is provided on a transparent film (Patent Document) 4) etc. are also proposed.
JP 2004-272197 A JP 2005-283611 A JP 2006-209050 A JP 2005-157037 A

  By the way, the conventional porous oxide particles having open pores have a large surface energy because the specific surface area of the particles themselves is very large. Therefore, when the porous oxide particles are dispersed in a dispersion medium, A binder component such as a dispersant or a resin contained in the dispersion medium not only adheres to the particle surface but also penetrates into the open holes and fills the open holes, resulting in sufficiently low refractive index and low dielectric constant. There is a problem that it is technically difficult to maintain the characteristics.

  Therefore, in order to solve this problem, it is also considered that the binder component such as resin does not enter the open hole by adjusting the composition, structure, molecular weight, etc. of the binder component such as resin, For example, a structure in which the open ends of vacancies formed on the surface of porous silica are covered with a high molecular silicon compound having a number average molecular weight of 2000 or more has been proposed (JP 2006-308898 A). There is a problem in that the synthesis of a polymeric silicon compound and the like is complicated and inferior in versatility.

On the other hand, the present inventors formed a large number of pores at least near the surface of the oxide particles so that the binder component such as resin does not enter the open pores, and these pores are formed on the surface. A surface-coated porous oxide particle having an open end in the open end, a capping agent in the open hole, and at least the open end sealed with a coating layer made of an organic polymer has been proposed (Japanese Patent Application No. 2007). -271202).
However, since the surface-coated porous oxide particles have a capping agent in the open pores, it is difficult to make the open pores hydrophilic and are manufactured through a number of steps. Therefore, there are problems such as complicated processes and difficulty in reducing manufacturing costs.

  The present invention has been made to solve the above-described problem, and even when porous oxide particles having open pores are dispersed in a dispersion medium, the dispersant, resin, etc. contained in the dispersion medium Surface-coated porous oxide particles that can prevent the binder component from penetrating into the open pores, and thus can maintain the characteristics of the porous oxide particles such as low refractive index and low dielectric constant, And it aims at providing the surface coating method of the porous oxide particle which can perform surface coating easily by the number of processes small compared with the past.

  As a result of intensive studies on improving the characteristics of the porous oxide particles, the present inventors have sealed the open ends of the open holes formed in the vicinity of the surface of the porous oxide particles with a coating layer made of an organic polymer. Furthermore, if the inside of the open pores is made hydrophilic, even when the porous oxide particles are dispersed in the dispersion medium, binder components such as a dispersant and a resin contained in the dispersion medium are contained in the open pores. The inventors have found that it is possible to maintain the characteristics of porous oxide particles such as low refractive index and low dielectric property without invading the liquid, and have completed the present invention.

  That is, the surface-coated porous oxide particles of the present invention are porous oxide particles in which a large number of pores are formed at least in the vicinity of the surface, and these pores are open pores having open ends on the surface. It is surface-coated porous oxide particles coated on the surface, and the open end is sealed with a coating layer made of an organic polymer, and the inside of the open hole is made hydrophilic. Features.

In the surface-coated porous oxide particles, it is preferable that the coating layer is fixed by being bonded to at least a part of the outer peripheral surface of the porous oxide particles.
The thickness of the coating layer is preferably 0.1 nm or more and 30 nm or less.
The average particle diameter of the porous oxide particles is preferably 0.01 μm or more and 10 μm or less, and the diameter of the open end is preferably 0.1 nm or more and 50 nm or less.
The porous oxide particles preferably contain one or more selected from the group consisting of silicon oxide, aluminum silicate, aluminum oxide, zirconium oxide, and titanium oxide as main components.
It is preferable that a volatile solvent having hydrophilicity is contained in the open hole.
The volatile solvent is preferably water.

  The porous oxide particle surface coating method of the present invention is a porous oxide particle in which a large number of pores are formed at least in the vicinity of the surface, and these pores are open pores having open ends on the surface. A method for coating a surface, the first step of adsorbing a volatile solvent having hydrophilicity in the open pores, and the second step of forming a reaction point on the outer peripheral surface of the porous oxide particles; A coating layer made of an organic polymer is bonded and fixed to at least a part of the outer peripheral surface of the porous oxide particle, and the opening end is sealed with the coating layer, and the opening in the open hole is And a third step of removing a volatile solvent.

  In the method of covering the surface of the porous oxide particles, it is preferable that the second and third steps are performed in a solvent that is incompatible with the volatile solvent.

  Another surface coating method of the porous oxide particles of the present invention is a porous oxide in which a large number of holes are formed at least in the vicinity of the surface, and these holes are open holes having an open end on the surface. A method of coating the surface of the particles, the first step of adsorbing a volatile solvent having hydrophilicity in the open pores, and the second step of forming reaction points on the outer peripheral surface of the porous oxide particles A step of drying the porous oxide particles to remove the volatile solvent in the open pores, and an organic polymer on at least a part of the outer peripheral surface of the porous oxide particles. And a fourth step of sealing and sealing the opening end with the coating layer.

  In the method of covering the surface of the porous oxide particles, it is preferable that the second and fourth steps are performed in a solvent that is incompatible with the volatile solvent.

In these porous oxide particle surface coating methods, the organic polymer is preferably insoluble in the volatile solvent.
The thickness of the coating layer is preferably 0.1 nm or more and 30 nm or less.
The average particle diameter of the porous oxide particles is preferably 0.01 μm or more and 10 μm or less, and the diameter of the open end is preferably 0.1 nm or more and 50 nm or less.
The porous oxide particles preferably contain one or more selected from the group consisting of silicon oxide, aluminum silicate, aluminum oxide, zirconium oxide, and titanium oxide as main components.
The volatile solvent is preferably water.

  According to the surface-coated porous oxide particles of the present invention, a large number of pores are formed at least in the vicinity of the surface, and these pores are open pores having open ends on the surface. The open end is sealed with a coating layer made of an organic polymer, and the inside of the open hole is made hydrophilic so that binder components such as a dispersant and a resin can be prevented from entering the open hole. it can. Therefore, characteristics as porous oxide particles such as low refractive index and low dielectric property can be maintained.

According to the surface coating method of the porous oxide particles of the present invention, the first step of adsorbing the volatile solvent having hydrophilicity in the open pores and the reaction points are formed on the outer peripheral surface of the porous oxide particles. A second step and a coating layer made of an organic polymer is bonded and fixed to at least a part of the outer peripheral surface of the porous oxide particle, and the opening end is sealed with the coating layer, and And a third step of removing the volatile solvent in the open hole, so that there is no possibility that a binder component such as a dispersant or a resin penetrates into the open hole, and the low refractive index property, low dielectric property, etc. Surface-coated porous oxide particles that can maintain the properties as porous oxide particles can be easily obtained with fewer steps than in the past.
In addition, since the number of processes can be reduced, the manufacturing process can be shortened and the manufacturing cost can be reduced.

According to the other surface coating method of the porous oxide particles of the present invention, the first step of adsorbing the volatile solvent having hydrophilicity in the open pores, and the reaction points on the outer peripheral surface of the porous oxide particles A second step of forming, a third step of drying the porous oxide particles to remove the volatile solvent in the open pores, and an organic polymer on at least a part of the outer peripheral surface of the porous oxide particles And a fourth step of sealing the open end with this coating layer, so that there is no risk of binder components such as dispersants and resins entering the open holes. Surface-coated porous oxide particles that can maintain the properties of porous oxide particles such as low refractive index and low dielectric property can be easily obtained with fewer steps than in the past.
In addition, since the number of processes can be reduced, the manufacturing process can be shortened and the manufacturing cost can be reduced.

The best mode for carrying out the surface-coated porous oxide particles and the method of coating the surface of porous oxide particles of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[First Embodiment]
The surface-coated porous oxide particles of the present embodiment have a large number of pores formed at least in the vicinity of the surface, and the surface of the porous oxide particles in which these pores are open pores having open ends on the surface. The open end is a surface-coated porous oxide particle, the open end is sealed with a coating layer made of an organic polymer, and the open hole is a hydrophilic particle.

Here, examples of the composition of the porous oxide particles include inorganic oxides such as silicon silicate and aluminum silicate such as zeolite, and metal oxides such as aluminum oxide, zirconium oxide, and titanium oxide. These silicon oxides, Aluminum silicate, aluminum oxide, zirconium oxide, titanium oxide and the like can be used by selecting one or more of them.
In consideration of covering the open holes with a coating layer made of an organic polymer generated from a surface coating agent, it is desirable that the reactivity with organic substances is low, and it is used as a low refractive index material, a low dielectric constant material, etc. In this case, since it is desirable that the material itself has a low refractive index and a low dielectric constant, silicon oxide is preferably the main component.

The average particle diameter of the porous oxide particles is preferably 0.01 μm or more and 10 μm or less, more preferably 0.03 μm or more and 3 μm or less, and further preferably 0.03 μm or more and 1 μm or less.
Here, the reason why the average particle diameter of the porous oxide particles is in the above range is that the above range is good for the properties of the porous oxide particles such as low refractive index and low dielectric constant over a long period of time. If the average particle size is less than 0.01 μm, the characteristics of the porous oxide particles are deteriorated. On the other hand, if the average particle size exceeds 10 μm, porous oxidation is not possible. Since the characteristics of the film or film to which the product particles are added deteriorate, it is not preferable.

  As for the diameter of the open end of the open hole of the porous oxide particle, in the porous oxide particle surface coating method to be described later, the porous hole is formed after the first step in which the volatile solvent is adsorbed in the open hole. During the second step of forming reactive sites on the outer peripheral surface of the oxide particles, the open hole is blocked by the adsorbed volatile solvent, and the opening of the open hole in the third step is the next step Considering that the end is sealed with a coating layer made of an organic polymer, it needs to be small to some extent. On the other hand, in order to adsorb the volatile solvent in the open hole, the open end of the open hole needs to have a diameter of about several times the molecule of the volatile solvent. From the above points, the diameter of the open end is preferably 0.1 nm or more and 50 nm or less, more preferably 1 nm or more and 10 nm or less, and further preferably 1 nm or more and 5 nm or less.

A coating layer made of an organic polymer that seals the opening end is fixed to at least a part of the outer peripheral surface of the porous oxide particles by bonding.
Here, the “outer peripheral surface” is the surface constituting the outer peripheral surface portion of the porous oxide particle, that is, the outer surface of the particle excluding the inner surface of the open pores among the entire surface of the porous oxide particle. It is a part.
The thickness of the coating layer is preferably 0.1 nm or more and 30 nm or less, more preferably 0.1 nm or more and 15 nm or less, and further preferably 0.5 nm or more and 10 nm or less.

Here, when the thickness of the coating layer is less than 0.1 nm, it is difficult to form the coating layer uniformly on the outer peripheral surface of the porous oxide particles, and when the open end of the open hole is sealed, This is because the coating strength of the sealed portion cannot be obtained sufficiently.
On the other hand, since the refractive index and dielectric constant of the coating layer are generally higher than the refractive index and dielectric constant of the porous oxide particles, if the thickness of the coating layer exceeds 30 nm, the influence of the coating layer increases and the low refractive index. This is because it becomes impossible to obtain a sufficient ratio and low dielectric constant.
In addition, in the drying step after sealing the open end of the open hole as will be described later, when the solvent remaining in the open hole is volatilized and removed through the coating layer, if the coating layer is thickened, This is because the removal cannot be performed sufficiently.

Examples of the organic polymer include methyl acrylate, methyl methacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexaacrylate. An organic resin obtained by condensation polymerization of monomers such as
In the surface-coated porous oxide particles, the inside of the open pores is hydrophilic, and thus the open pores may contain a volatile solvent having hydrophilicity in the gas phase or liquid phase. As the volatile solvent having hydrophilicity, not only water but also a low-boiling organic solvent having compatibility with water, for example, ethanol, 2-propanol and the like can be mentioned.

"Surface coating method for porous oxide particles"
The porous oxide particle surface covering method of this embodiment is a porous oxide particle in which a large number of pores are formed at least in the vicinity of the surface, and these pores are open pores having open ends on the surface. A first step of adsorbing a volatile solvent having hydrophilicity in the open pores, and a second step of forming reaction points on the outer peripheral surface of the porous oxide particles And a coating layer made of an organic polymer is bonded and fixed to at least a part of the outer peripheral surface of the porous oxide particle, and the opening end is sealed with the coating layer, and the inside of the open hole And a third step of removing the volatile solvent.

Next, the surface covering method of the porous oxide particles will be described in detail for each step based on FIG.
"First step"
In this first step, a volatile solvent 4 having a gas phase or liquid phase hydrophilic property is adsorbed in the outer peripheral surface 2 and the open hole 3 of the porous oxide particle 1, and the inside of the open hole is gas phase or This is a step of closing the open holes 3 by filling with a volatile solvent 4 having a hydrophilic liquid phase (FIGS. 1A to 1B).

As the volatile solvent 4, water is suitable. In order to adsorb water to the porous oxide particles 1, the porous oxide particles 1 and a water vapor source are placed in a sealed container, and the inside of the sealed container is brought into a state close to saturation with water vapor generated from the water vapor source. A method of adsorbing water to the porous oxide particles 1 is employed.
When the porous oxide particle 1 is silicon oxide, it can be adsorbed to the inside of the open pores with a relative humidity of about 70 to 80%. Therefore, as a water vapor source, NaCl, NaNO ₃ , NH ₄ Cl having a high saturated vapor pressure can be used. Saturated aqueous solution of KBr, KCl, etc. is desirable.

"Second step"
This 2nd process is a process of forming the reaction point 5 in the outer peripheral surface 2 of the porous oxide particle 1 by which the open hole 3 was block | closed with the volatile solvent 4 (FIG.1 (c)).
As a reaction point forming agent for forming the reaction point, when the material of the coating layer bonded to the reaction point 5 is an acrylic monomer such as methyl methacrylate or methyl acrylate, an acrylic group or a vinyl group is used. A silane coupling agent, a surface coupling agent, or the like can be used.

The solvent for dissolving the reaction point forming agent is preferably a volatile solvent 4 adsorbed on the porous oxide particles 1, for example, a non-aqueous solvent that is incompatible with water.
As a method for forming this reaction point, a supercritical method using an autoclave using hexane or carbon dioxide as a medium, or a reflux method using a hydrocarbon such as toluene or xylene, or a ketone such as methyl isobutyl ketone as a medium. Is mentioned.

  In this step, since the volatile solvent 4 adsorbed on the outer peripheral surface of the porous oxide particle 1, for example, water is in direct contact with the non-aqueous solvent used in this step, the reaction points contained in this non-aqueous solvent A forming agent, for example, a coupling agent is consumed by the reaction of binding to the outer peripheral surface of the porous oxide particle 1 by hydrolysis, that is, the formation of the reaction point 5. On the other hand, the inside of the open hole 3 is filled with the adsorbed volatile solvent 4, for example, water, and the solvent used in this step is a non-aqueous solvent, so that the non-aqueous solvent enters the open hole 3. Therefore, the volatile solvent 4 adsorbed in the open hole 3, such as water, is not consumed, and no reaction point is formed in the open hole 3.

Therefore, the reaction point 5 is selectively formed on the outer peripheral surface 2 of the porous oxide particle 1 by this step.
In this step, when an aqueous solvent is used as a solvent for dissolving the reaction point forming agent, the aqueous solvent will flow into the open hole 3, and thus react with the inner surface of the open hole 3. Since a point will be formed, it is not preferable.

"Third process"
In this third step, a coating layer 6 made of an organic polymer is bonded and fixed to the reaction point 5 formed on the outer peripheral surface 2 of the porous oxide particle 1, and the open layer 3 is formed by this coating layer 6. This is a step of sealing the open end and removing the volatile solvent 4 adsorbed in the open hole 3 (FIG. 1 (d)).

As the surface coating agent for forming the coating layer 6 made of an organic polymer, a monomer or oligomer that is a raw material for the organic polymer is preferable, and these monomers and oligomers are used alone or in combination. be able to.
The surface coating agent must be selected according to the nature of the reaction point 5, that is, the reaction point forming agent. For example, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxy can be used as the reaction point forming agent. When using a silane coupling agent having an acrylic group and / or vinyl group such as silane and vinyltrimethoxysilane, it is possible to use one or more functional acrylic monomers, methacrylic monomers and vinyl monomers alone or in combination. it can.

  Examples of these monomers include methyl acrylate, methyl methacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexa An acrylate etc. are mentioned.

In this step, the surface coating agent and the porous oxide particles 1 having the reaction points 5 formed on the outer peripheral surface 2 are added to a solvent, and an inert gas such as nitrogen is added while stirring the obtained solution. After aeration and sufficient removal of oxygen in the solution, a polymerization (or reaction) initiator such as a radical generator is added, and the surface coating monomer adsorbed on the outer peripheral surface 2 of the porous oxide particle 1 or The oligomer is polymerized (or reacted) to form a coating layer 6 made of an organic polymer.
Further, the volatile solvent 4 adsorbed in the open holes 3, for example, water may be removed by stirring the solution and venting with an inert gas.

  At this time, it is more preferable to selectively form the coating layer 6 on the outer peripheral surface 2 of the porous oxide particle 1, and it is also effective to select and use a solvent while paying attention to the solubility parameter of the monomer. This is because if the surface coating agent to be used is more familiar with the porous oxide particles 1 in which the reaction points 5 are formed than the solvent, the added surface coating agent is concentrated on the outer peripheral surface 2 of the porous oxide particles 1. This is because the coating layer 6 can be efficiently formed.

Moreover, it is necessary to select the solvent to be used that does not cause a chemical change by the polymerization (or reaction) initiator. For example, as a polymerization (or reaction) initiator, the solvent used when the radical generator as described above is used includes hydrocarbon solvents, pentane, hexane, heptane, octane, toluene, xylene, etc. These solvents can be used alone or in combination of two or more.
As the polymerization (or reaction) initiator, a thermal radical generator that generates radicals at a predetermined temperature, a photo radical generator that generates radicals upon irradiation with ultraviolet rays, or the like is used. As the thermal radical generator, benzoyl peroxide, azobisisobutyl nitrile and the like are suitably used, and as the photo radical generator, benzophenone and the like are suitably used.

When a silane coupling agent having an amino group such as N-2 (aminoethyl) 3-aminopropyltrimethoxysilane or 3-aminopropyltrimethoxysilane is used as the reaction point forming agent, The coating layer 6 can be formed by adding a high molecular polymer having an acid and amidating the polymer.
In addition, the coating layer 6 can also be formed by adding glutaraldehyde in a phosphate buffer solution and then adding an amino group-containing polymer or an amino acid such as histidine. In this case, the solvent used is not particularly defined, but water is generally used.

When the coating layer 6 is formed, the surface coating agent is also bonded to the reaction point 5 by the polymerization (or reaction) initiator, so that the surface coating agent forms the coating layer 6 by polymerization, and at the same time, the porous oxide. Fixed to the outer peripheral surface 2 of the particle 1. Thereby, the coating layer 6 is formed only on the outer peripheral surface 2 of the porous oxide particle 1.
Further, since the covering layer 6 is formed from the peripheral edge of the open end 3 toward the center of the open end of the open hole 3, the open end is finally sealed with the cover layer 6. It will be.

Since no reaction point 5 is formed on the inner surface of the open hole 3, no coating layer is formed on the inner surface of the open hole 3.
As described above, since the open end 3 of the open hole 3 is sealed with the coating layer 6 while holding the internal void, the coating layer 6 can be formed on the porous oxide particles 1.

Finally, the porous oxide particles 1 on which the coating layer 6 is formed are separated from the solvent, washed and dried to obtain surface-coated porous oxide particles.
Here, the sealed open hole 3 contains the adsorbed volatile solvent 4, for example, water and the solvent in the third step, but these are volatilized and removed during the main drying step. The This is because the coating layer 6 that seals the open end of the open hole 3 is not a completely dense film, such as the volatile solvent 4 adsorbed in the open hole or the solvent in the third step. This is because low molecular weight substances can pass through the membrane.

  Therefore, as drying conditions, it is desirable to select a temperature and time sufficient to remove the volatile solvent 4 and the solvent in the third step. The type of the volatile solvent 4 and the type of the solvent in the third step In addition, the material and thickness of the formed coating layer 6 are also taken into consideration. For example, when water is used as the volatile solvent 4 and toluene is used as the solvent in the third step, and the film thickness is 1 to 30 nm, drying may be performed at 80 ° C. to 150 ° C. for about 1 hour to 15 hours. preferable. It is also preferable to perform dry atmosphere control such as decompression and introduction of a dry gas.

  According to the surface-coated porous oxide particles of this embodiment, a large number of pores are formed in the vicinity of the surface of the porous oxide particles 1, and these pores are formed as open holes 3 having open ends on the surface. Since the open end of the open hole 3 is sealed with a coating layer 6 made of an organic polymer and the open hole 3 is made hydrophilic, a binder component such as a dispersant or a resin enters the open hole 3. Therefore, the characteristics of the porous oxide particles 1 such as low refractive index and low dielectric constant can be maintained.

  According to the porous oxide particle surface coating method of the present embodiment, the first step of adsorbing the volatile solvent 4 having hydrophilicity in the open holes 3 and the outer peripheral surface 2 of the porous oxide particles 1 are applied. The second step of forming the reaction point 5 and the coating layer 6 made of an organic polymer are bonded and fixed to the outer peripheral surface 2 of the porous oxide particle 1, and the open end of the open hole 3 is fixed by this coating layer 6. And the third step of removing the volatile solvent 4 in the open holes 3, the surface-coated porous oxide particles of this embodiment can be easily obtained.

[Second Embodiment]
In the method of covering the surface of the porous oxide particles according to the second embodiment of the present invention, a large number of holes are formed at least in the vicinity of the surface, and these holes are open holes having open ends on the surface. A method for coating the surface of porous oxide particles, a first step of adsorbing a volatile solvent having hydrophilicity in the open pores, and a second step of forming reaction points on the outer peripheral surface of the porous oxide particles And at least part of the outer peripheral surface of the porous oxide particles, the third step of drying the outer peripheral surface of the porous oxide particles and the inside of the open pores to remove the volatile solvent in the open pores, A fourth step of bonding and fixing a coating layer made of an organic polymer, and sealing the open end with the coating layer.

Next, the surface coating method of the porous oxide particles will be described in detail for each step based on FIG.
The first and second steps in the porous oxide particle surface coating method are exactly the same as the first and second steps in the porous oxide particle surface coating method of the first embodiment. Therefore, the description is omitted.

"Third process"
This third step is a step of drying the outer peripheral surface 2 of the porous oxide particles 1 and the inside of the open holes 3 to remove the volatile solvent 4 adsorbed in the open holes 3 (FIG. 2 (d). )).
The drying conditions may be any temperature and time sufficient to remove the volatile solvent 4.
For example, in the case of water, the drying temperature is 80 ° C. or more and 150 ° C. or less, and the drying time is 1 hour or more and 15 hours or less.
Thereby, the volatile solvent 4 adsorbed in the open hole 3, for example, water is removed.

"Fourth process"
In this fourth step, a coating layer 6 made of an organic polymer is bonded and fixed to at least a part of the outer peripheral surface 2 of the porous oxide particle 1, and the open end of the open hole 3 is fixed by this coating layer 6. Is a step of sealing (FIG. 2E).
The surface coating agent and solvent used in this step and the method for forming the coating layer 6 are exactly the same as those in the third step in the surface coating method for porous oxide particles of the first embodiment.

Also in this step, as in the third step of the first embodiment, when the coating layer 6 is formed, the surface coating agent is also bonded to the reaction point 5 by the polymerization (or reaction) initiator. The surface coating agent is fixed to the outer peripheral surface 2 of the porous oxide particle 1 at the same time as forming the coating layer 6 by polymerization. Thereby, the coating layer 6 is formed only on the outer peripheral surface 2 of the porous oxide particle 1.
Further, since the covering layer 6 is formed from the peripheral edge of the open end 3 toward the center of the open end of the open hole 3, the open end is finally sealed with the cover layer 6. It will be.

Since no reaction point 5 is formed on the inner surface of the open hole 3, no coating layer is formed on the inner surface of the open hole 3.
As described above, since the open end 3 of the open hole 3 is sealed with the coating layer 6 while holding the internal void, the coating layer 6 can be formed on the porous oxide particles 1.

  In the present embodiment, since the volatile solvent 4 is removed in the third step, the volatile solvent 4 is not contained in the sealed open hole 3 but is used in the fourth step. Some solvents may remain. Similar to the first embodiment, the residual solvent can be removed by separating the porous oxide particles 1 on which the coating layer 6 is formed from the solvent, washing, and drying.

Also in the surface covering method of the porous oxide particles of the present embodiment, the same actions and effects as the surface covering method of the porous oxide particles of the first embodiment can be achieved.
Moreover, in the surface coating method according to the first embodiment, the first step is to remove the volatile solvent in the open pores by drying the outer peripheral surface of the porous oxide particles and the inside of the open pores. Two steps of a step and a fourth step of bonding and fixing a coating layer made of an organic polymer to at least a part of the outer peripheral surface of the porous oxide particles, and sealing the open end with the coating layer Therefore, the volatile solvent 4 in the open hole 3 can be reliably removed.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

"Example 1"
(1) Water adsorption Nanoporous silica (open pore size: 2-3 nm, average particle size: 50 nm, internal porosity: 50%, manufactured by Sumitomo Osaka Cement) is used as the porous oxide particles. Silica and saturated saline were allowed to stand in a desiccator (sealed container) for 5 days, and adsorbed until the pores of nanoporous silica were filled with saturated water vapor.

(2) Formation of reaction point 10 g of nanoporous silica adsorbed with water was added to 200 mL of toluene, refluxed at the boiling point of toluene for 1 hour, and then 2.1 g of 3-acryloxypropyltrimethoxysilane was added. Reflux for a period of time.
Then, it cooled to room temperature, isolate | separated and wash | cleaned, and obtained the nanoporous silica A which formed the reaction point in the outer peripheral surface.

(3) Surface coating 0.5 g of this nanoporous silica A was dispersed in 200 mL of toluene, and 0.05 mL of methyl methacrylate and 0.44 mL of ethylene glycol dimethacrylate were added to the resulting dispersion, followed by stirring at 60 ° C. for 1 hour. went.
Next, 0.08 g of 2,2-azobisisobutyronitrile was added while flowing dry nitrogen, and the mixture was reacted at 60 ° C. for 1 hour, and then 200 mL of hexane was added and separated using a centrifuge.

  Next, 10 mL of toluene is added to the separated paste-like material, stirred, and then separated by a centrifuge. The operation of discarding the supernatant and collecting the paste-like material is repeated three times, Using a dryer, drying was performed at 150 ° C. for 12 hours to obtain surface-coated porous oxide particles A of Example 1. In FIG. 3, the scanning electron microscope (SEM) image of this surface covering porous oxide particle A is shown.

(4) Preparation of thin film for evaluation 1.5 g of Acrydic 52-101 (manufactured by Dainippon Ink & Chemicals, Inc.) was added to 3.5 g of toluene and stirred to obtain a binder.
Subsequently, these were mixed so that it might become 1.28 mass parts of binders and 3.55 mass parts of toluene, and 0.17 mass part of surface covering porous oxide particle A was added and disperse | distributed to this, and the coating material A was obtained. .
Subsequently, the coating material A was apply | coated on the acrylic substrate by spin coat, and the obtained coating film was dried and then heated and cured at 80 ° C. for 20 minutes to obtain a thin film A. The spin coating was performed at a rotational speed of 1000 to 2000 rpm-30 seconds.

"Example 2"
(1) Water adsorption Nanoporous silica (open pore size: 2-3 nm, average particle size: 50 nm, internal porosity: 50%, manufactured by Sumitomo Osaka Cement) is used as the porous oxide particles. Silica and saturated saline were allowed to stand in a desiccator (sealed container) for 5 days, and adsorbed until the pores of nanoporous silica were filled with saturated water vapor.

(2) Formation of reaction point 10 g of nanoporous silica adsorbed with water was added to 200 mL of toluene, refluxed at the boiling point of toluene for 1 hour, and then 2.1 g of 3-acryloxypropyltrimethoxysilane was added. Reflux for a period of time.
Then, it cooled to room temperature, isolate | separated and wash | cleaned, and obtained the nanoporous silica B which formed the reaction point in the outer peripheral surface.

(3) Surface coating Disperse 0.5 g of this nanoporous silica B in 200 mL of toluene, add 0.012 mL of methyl methacrylate and 0.11 mL of ethylene glycol dimethacrylate to the resulting dispersion, and stir at 60 ° C. for 1 hour. went.
Next, 0.02 g of 2,2-azobisisobutyronitrile was added while flowing dry nitrogen, and the mixture was reacted at 60 ° C. for 1 hour, and then 200 mL of hexane was added and separated using a centrifuge.

  Next, 10 mL of toluene is added to the separated paste-like material, stirred, and then separated by a centrifuge. The operation of discarding the supernatant and collecting the paste-like material is repeated three times, Using a dryer, drying was performed at 150 ° C. for 12 hours to obtain surface-coated porous oxide particles B of Example 2.

(4) Preparation of thin film for evaluation 1.5 g of Acrydic 52-101 (manufactured by Dainippon Ink & Chemicals, Inc.) was added to 3.5 g of toluene and stirred to obtain a binder.
Subsequently, these were mixed so that it might become 1.28 mass parts of binders and 3.55 mass parts of toluene, and 0.17 mass parts of surface covering porous oxide particle B was added and disperse | distributed to this, and the coating material B was obtained. .
Next, the coating material B was applied onto an acrylic substrate by spin coating, and the obtained coating film was dried and then cured by heating at 80 ° C. for 20 minutes to obtain a thin film B. The spin coating was performed at a rotational speed of 1000 to 2000 rpm-30 seconds.

"Example 3"
(1) Water adsorption Nanoporous silica (open pore size: 2-3 nm, average particle size: 50 nm, internal porosity: 50%, manufactured by Sumitomo Osaka Cement) is used as the porous oxide particles. Silica and saturated saline were allowed to stand in a desiccator (sealed container) for 5 days, and adsorbed until the pores of nanoporous silica were filled with saturated water vapor.

(2) Formation of reaction point 10 g of nanoporous silica adsorbed with water was added to 200 mL of toluene, refluxed at the boiling point of toluene for 1 hour, and then 2.1 g of 3-acryloxypropyltrimethoxysilane was added. Reflux for a period of time.
Then, it cooled to room temperature, isolate | separated and wash | cleaned, and obtained the nanoporous silica C which formed the reaction point in the outer peripheral surface.

(3) Surface coating Disperse 0.5 g of this nanoporous silica C in 200 mL of toluene, add 0.005 mL of methyl methacrylate and 0.044 mL of ethylene glycol dimethacrylate to the resulting dispersion, and stir at 60 ° C. for 1 hour. went.
Next, 0.008 g of 2,2-azobisisobutyronitrile was added while flowing dry nitrogen, and the mixture was reacted at 60 ° C. for 1 hour, and then 200 mL of hexane was added and separated using a centrifuge.

  Next, 10 mL of toluene is added to the separated paste-like material, stirred, and then separated by a centrifuge. The operation of discarding the supernatant and collecting the paste-like material is repeated three times, Using a drier, drying was performed at 150 ° C. for 12 hours to obtain surface-coated porous oxide particles C of Example 3.

(4) Preparation of thin film for evaluation 1.5 g of Acrydic 52-101 (manufactured by Dainippon Ink & Chemicals, Inc.) was added to 3.5 g of toluene and stirred to obtain a binder.
Subsequently, these were mixed so that it might become 1.28 mass parts of binders and 3.55 mass parts of toluene, and 0.17 mass part of surface covering porous oxide particle C was added and disperse | distributed to this, and the coating material C was obtained. .
Next, the coating material C was applied onto an acrylic substrate by spin coating, and the obtained coating film was dried and then heated and cured at 80 ° C. for 20 minutes to obtain a thin film C. The spin coating was performed at a rotational speed of 1000 to 2000 rpm-30 seconds.

Example 4
(1) Water adsorption Nanoporous silica (open pore diameter: 2-3 nm, average particle diameter: 400 nm, internal porosity: 62%, manufactured by Sumitomo Osaka Cement) is used as the porous oxide particles. Silica and saturated saline were allowed to stand in a desiccator (sealed container) for 5 days, and adsorbed until the pores of nanoporous silica were filled with saturated water vapor.

(2) Formation of reaction point 10 g of nanoporous silica adsorbed with water was added to 200 mL of toluene, refluxed at the boiling point of toluene for 1 hour, and then 2.1 g of 3-acryloxypropyltrimethoxysilane was added. Reflux for a period of time.
Then, it cooled to room temperature, isolate | separated and wash | cleaned, and obtained the nanoporous silica D which formed the reaction point in the outer peripheral surface.

(3) Surface coating Disperse 0.5 g of this nanoporous silica D in 200 mL of toluene, add 0.013 mL of methyl methacrylate and 0.15 mL of ethylene glycol dimethacrylate to the resulting dispersion, and stir at 60 ° C. for 1 hour. went.
Next, 0.025 g of 2,2-azobisisobutyronitrile was added while flowing dry nitrogen, and the mixture was reacted at 60 ° C. for 1 hour, and then 200 mL of hexane was added and separated using a centrifuge.

  Next, 10 mL of toluene is added to the separated paste-like material, stirred, and then separated by a centrifuge. The operation of discarding the supernatant and collecting the paste-like material is repeated three times, Using a dryer, drying was performed at 150 ° C. for 12 hours to obtain surface-coated porous oxide particles D of Example 4.

(4) Preparation of thin film for evaluation 1.5 g of Acrydic 52-101 (manufactured by Dainippon Ink & Chemicals, Inc.) was added to 3.5 g of toluene and stirred to obtain a binder.
Subsequently, these were mixed so that it might become 1.28 mass parts of binders, and 3.55 mass parts of toluene, and 0.17 mass part of surface covering porous oxide particle D was added and disperse | distributed to this, and the coating material D was obtained. .
Next, the coating material D was applied onto an acrylic substrate by spin coating, and the obtained coating film was dried and then heated and cured at 80 ° C. for 20 minutes to obtain a thin film D. The spin coating was performed at a rotational speed of 1000 to 2000 rpm-30 seconds.

"Example 5"
(1) Water adsorption Nanoporous silica (open pore size: 2-3 nm, average particle size: 9500 nm, internal porosity: 69%, manufactured by Sumitomo Osaka Cement) is used as the porous oxide particles. Silica and saturated saline were allowed to stand in a desiccator (sealed container) for 5 days, and adsorbed until the pores of nanoporous silica were filled with saturated water vapor.

(2) Formation of reaction point 10 g of nanoporous silica adsorbed with water was added to 200 mL of toluene, refluxed at the boiling point of toluene for 1 hour, and then 2.1 g of 3-acryloxypropyltrimethoxysilane was added. Reflux for a period of time.
Then, it cooled to room temperature, isolate | separated and wash | cleaned, and obtained the nanoporous silica E which formed the reaction point in the outer peripheral surface.

(3) Surface coating Disperse 0.5 g of this nanoporous silica E in 200 mL of toluene, add 0.005 mL of methyl methacrylate and 0.044 mL of ethylene glycol dimethacrylate to the obtained dispersion, and stir at 60 ° C. for 1 hour. went.
Next, 0.008 g of 2,2-azobisisobutyronitrile was added while flowing dry nitrogen, and the mixture was reacted at 60 ° C. for 1 hour, and then 200 mL of hexane was added and separated using a centrifuge.

  Next, 10 mL of toluene is added to the separated paste-like material, stirred, and then separated by a centrifuge. The operation of discarding the supernatant and collecting the paste-like material is repeated three times, Using a drier, drying was performed at 150 ° C. for 12 hours to obtain surface-coated porous oxide particles E of Example 5.

(4) Preparation of thin film for evaluation 1.5 g of Acrydic 52-101 (manufactured by Dainippon Ink & Chemicals, Inc.) was added to 3.5 g of toluene and stirred to obtain a binder.
Subsequently, these were mixed so that it might become 1.28 mass parts of binders and 3.55 mass parts of toluene, and 0.17 mass parts of surface covering porous oxide particles E were added and disperse | distributed to this, and the coating material E was obtained. .
Subsequently, the coating material E was apply | coated on the acrylic substrate by spin coat, and the obtained coating film was dried and then heated and cured at 80 ° C. for 20 minutes to obtain a thin film E. The spin coating was performed at a rotational speed of 1000 to 2000 rpm-30 seconds.

"Example 6"
(1) Water adsorption Nanoporous silica (open pore size: 2-3 nm, average particle size: 50 nm, internal porosity: 50%, manufactured by Sumitomo Osaka Cement) is used as the porous oxide particles. Silica and saturated saline were allowed to stand in a desiccator (sealed container) for 5 days, and adsorbed until the pores of nanoporous silica were filled with saturated water vapor.

(2) Formation of reaction point 10 g of nanoporous silica adsorbed with water was added to 200 mL of toluene, refluxed at the boiling point of toluene for 1 hour, and then 2.1 g of 3-acryloxypropyltrimethoxysilane was added. Reflux for a period of time.
Then, it cooled to room temperature, isolate | separated and wash | cleaned, and obtained the nanoporous silica F which formed the reaction point in the outer peripheral surface.

(3) Drying This nanoporous silica F was dried by heating at 120 ° C. for 5 hours using a dryer.

(4) Surface coating 0.5 g of this dried nanoporous silica F was dispersed in 200 mL of toluene, and 0.05 mL of methyl methacrylate and 0.44 mL of ethylene glycol dimethacrylate were added to the resulting dispersion, followed by stirring at 60 ° C. for 1 hour. Went.
Next, 0.08 g of 2,2-azobisisobutyronitrile was added while flowing dry nitrogen, and the mixture was reacted at 60 ° C. for 1 hour, and then 200 mL of hexane was added and separated using a centrifuge.

  Next, 10 mL of toluene is added to the separated paste-like material, stirred, and then separated by a centrifuge. The operation of discarding the supernatant and collecting the paste-like material is repeated three times, Using a drier, drying was performed at 150 ° C. for 12 hours to obtain surface-coated porous oxide particles F of Example 6.

(5) Preparation of thin film for evaluation 1.5 g of Acrydic 52-101 (manufactured by Dainippon Ink & Chemicals, Inc.) was added to 3.5 g of toluene and stirred to obtain a binder.
Subsequently, these were mixed so that it might become 1.28 mass parts of binders and 3.55 mass parts of toluene, and it added and disperse | distributed 0.17 mass parts of surface covering porous oxide particles F, and the coating material F was obtained. .
Next, the coating material F was applied onto an acrylic substrate by spin coating, and the obtained coating film was dried and then heated and cured at 80 ° C. for 20 minutes to obtain a thin film F. The spin coating was performed at a rotational speed of 1000 to 2000 rpm-30 seconds.

“Comparative Example 1”
(1) Inactivation of inner surface of open pores As porous oxide particles, nanoporous silica (pore size of open pores: 2-3 nm, average particle size: 50 nm, internal porosity: 50%, manufactured by Sumitomo Osaka Cement) 10 g of this nanoporous silica was added to 200 mL of toluene in an untreated state, and 20 g of 1,1,1,3,3,3 hexamethyldisilazane was added, and toluene was blown into the toluene solution while blowing dry nitrogen. At the boiling point of 24 hours.
Then, it cooled to room temperature, isolate | separated and wash | cleaned, and obtained the nanoporous silica which made the particle | grain surface trimethylsilylation.

  Next, 3 g of this nanoporous silica was added to 100 mL of toluene, and the nanoporous silica in which the trimethylsilyl group was removed only from the outer peripheral surface by treating the particles with an ultrasonic homogenizer (Sonifier 450: manufactured by BRANSON) for 60 minutes to make the particles collide with each other. A treatment solution containing was obtained.

(2) Formation of reaction point Toluene 500 mL was added to the above treatment solution, 1.0 g of 3-acryloxypropyltrimethoxysilane was further added, and the resulting solution was again boiled with dry nitrogen at a boiling point of toluene of 24. Time reflux was performed.
Then, it cooled to room temperature, isolate | separated and wash | cleaned, and obtained the surface treatment particle | grains G which formed the reaction point on the surface.

(3) Surface coating Disperse 0.5 g of surface-treated particles G in 200 mL of toluene, add 0.05 mL of methyl methacrylate and 0.44 mL of ethylene glycol dimethacrylate to the resulting dispersion, and stir at 60 ° C. for 1 hour. It was.
Next, 0.08 g of 2,2-azobisisobutyronitrile was added while flowing dry nitrogen, and the mixture was reacted at 60 ° C. for 1 hour, and then 200 mL of hexane was added and separated using a centrifuge.

  Next, 10 mL of toluene is added to the separated paste-like material, stirred, and then separated by a centrifuge. The operation of discarding the supernatant and collecting the paste-like material is repeated three times, Using a dryer, drying was performed at 150 ° C. for 12 hours to obtain surface-coated porous oxide particles G of Comparative Example 1.

(4) Preparation of thin film for evaluation 1.5 g of Acrydic 52-101 (manufactured by Dainippon Ink & Chemicals, Inc.) was added to 3.5 g of toluene and stirred to obtain a binder.
Subsequently, these were mixed so that it might become 1.28 mass parts of binders and 3.55 mass parts of toluene, and 0.17 mass parts of surface covering porous oxide particles G were added and disperse | distributed to this, and the coating material G was obtained. .
Next, the coating material G was applied onto an acrylic substrate by spin coating, and the obtained coating film was dried and then cured by heating at 80 ° C. for 20 minutes to obtain a thin film G. The spin coating was performed at a rotational speed of 1000 to 2000 rpm-30 seconds.

“Comparative Example 2”
(1) Formation of reaction point As porous oxide particles, nanoporous silica (open pore size: 2-3 nm, average particle size: 50 nm, internal porosity: 50%, manufactured by Sumitomo Osaka Cement) was used. In an untreated state, 10 g of nanoporous silica was added to 200 mL of toluene, and refluxed at the boiling point of toluene for 1 hour. Thereafter, 2.1 g of 3-acryloxypropyltrimethoxysilane was added, and the mixture was further refluxed for 3 hours.
Then, it cooled to room temperature, isolate | separated and wash | cleaned, and obtained the surface treatment particle | grains H which formed the reaction point on the surface.

(2) Surface coating Disperse 0.5 g of surface-treated particles H in 200 mL of toluene, add 0.05 mL of methyl methacrylate and 0.44 mL of ethylene glycol dimethacrylate to the resulting dispersion, and stir at 60 ° C. for 1 hour. It was.
Next, 0.08 g of 2,2-azobisisobutyronitrile was added while flowing dry nitrogen, and the mixture was reacted at 60 ° C. for 1 hour, and then 200 mL of hexane was added and separated using a centrifuge.

  Next, 10 mL of toluene is added to the separated paste-like material, stirred, and then separated by a centrifuge. The operation of discarding the supernatant and collecting the paste-like material is repeated three times, Drying was performed at 150 ° C. for 12 hours using a dryer, and surface-coated porous oxide particles H of Comparative Example 2 were obtained.

(3) Preparation of thin film for evaluation 1.5 g of Acrydic 52-101 (manufactured by Dainippon Ink & Chemicals, Inc.) was added to 3.5 g of toluene and stirred to obtain a binder.
Subsequently, these were mixed so that it might become 1.28 mass parts of binders and 3.55 mass parts of toluene, and it added and disperse | distributed 0.17 mass parts of surface covering porous oxide particles, and the coating material H was obtained. .
Next, the coating material H was applied onto an acrylic substrate by spin coating, and the obtained coating film was dried and then cured by heating at 80 ° C. for 20 minutes to obtain a thin film H. The spin coating was performed at a rotational speed of 1000 to 2000 rpm-30 seconds.

“Comparative Example 3”
(1) Formation of reaction point As porous oxide particles, nanoporous silica (open pore size: 2-3 nm, average particle size: 50 nm, internal porosity: 50%, manufactured by Sumitomo Osaka Cement) was used. In an untreated state, 10 g of nanoporous silica was added to 200 mL of toluene, and refluxed at the boiling point of toluene for 1 hour. Thereafter, 2.1 g of 3-acryloxypropyltrimethoxysilane was added, and the mixture was further refluxed for 3 hours.
Then, it cooled to room temperature, isolate | separated and wash | cleaned, and obtained the surface treatment particle | grains I which formed the reaction point on the surface.

(2) Preparation of thin film for evaluation 1.5 g of Acrydic 52-101 (manufactured by Dainippon Ink & Chemicals, Inc.) was added to 3.5 g of toluene and stirred to obtain a binder.
Subsequently, these were mixed so that it might become 1.28 mass parts of binders and 3.55 mass parts of toluene, and 0.17 mass parts of surface treatment particle | grains I were added and disperse | distributed to this, and the coating material I was obtained.
Next, the coating material I was applied onto an acrylic substrate by spin coating, and the obtained coating film was dried and then cured by heating at 80 ° C. for 20 minutes to obtain a thin film I. The spin coating was performed at a rotational speed of 1000 to 2000 rpm-30 seconds.

"Evaluation"
Each of the surface-coated porous oxide particles A to H and the surface-treated particles I and the thin films A to I obtained in Examples 1 to 6 and Comparative Examples 1 to 3 was evaluated. Comparative Example 4 is an evaluation of only the acrylic substrate used above.
Evaluation items and evaluation methods are as follows.
(1) Amount of coating layer From the mass reduction rate when the surface-coated porous oxide particles A to H and the surface-treated particles I are heated from 200 ° C. to 450 ° C. with a thermal analyzer Thermo Plus TG8120 (manufactured by Rigaku Corporation), The coating layer amount (percentage) with respect to the entire particles was calculated.

(2) Reflectance The paints A to I are applied to each acrylic substrate to form thin films A to I on the surface of the acrylic substrate, and the back surface of these acrylic substrates is blackened with black magic, and then the spectrophotometer UV3150 (Manufactured by Shimadzu Corporation) was used to measure a 5 ° regular reflectance at a measurement light wavelength of 500 nm to 600 nm on the surfaces of the thin films A to I, and this average reflectance was taken as the reflectance.
(3) Pore retention rate From the “reflectance” obtained as described above, the refractive index of the thin films A to I is calculated using the Fresnel equation, and the refractive index, the resin and particles in the thin films A to I, and From the volume ratio, the refractive index of the particles was calculated, and the void retention was determined from this refractive index.
(4) Film thickness of the coating layer From the “coating layer amount” and “pore retention ratio” obtained above, “average particle diameter of nanoporous silica” and “specific gravity of silica (2.38)”, The film thickness was calculated.
These results are shown in Table 1.

From the above results, the following was found.
Comparing Examples 1 to 6 and Comparative Examples 2 to 3, Examples 1 to 6 clearly have a higher porosity retention rate, and the opening of open holes by a polymer coating method using water adsorption treatment It was confirmed that the edges were covered and satisfactorily prevented the binder component from entering the open holes.
Further, the process is simplified as compared with Comparative Example 1, and the time required for the process is also shortened.

  On the other hand, Comparative Example 1 is surface-coated porous oxide particles prepared by the method already proposed by the inventors of the present application (Japanese Patent Application No. 2007-271202), and has almost the same characteristics as those of Examples 1 to 5. However, the process is more complicated than those of Examples 1 to 5, and the time required for the process is long.

In Examples 1 and 2, the porosity retention decreased as the coating layer amount increased. This is because the number of particles in the thickness direction increased due to the increase in the coating layer thickness. Intrusion of the binder component into the inside is prevented.
In Example 3, the coating layer thickness is thin and the hole retention rate is also reduced. This is presumably because the covering of the open end of the open hole was not complete, and the binder had penetrated into the open hole.

In Examples 4 to 5, the larger the particle diameter, the higher the pore retention rate. This is because the volume of the nanoporous silica particles themselves is very large compared to the volume of the coating layer, and thus the coating layer This is thought to be because it is less affected.
Example 6 is a coating layer formed under the same conditions as in Example 1 except that nanoporous silica F with reaction points formed on the outer peripheral surface was heated at 120 ° C. for 5 hours and dried. A coating layer equivalent to that of Example 1 was formed, and it was found that the surface-coated porous oxide particles obtained in Example 1 and Example 6 were not different.

In Comparative Example 2, the open end of the open hole was covered without performing the water adsorption treatment, so that the polymer entered the open hole and the hole retention rate was reduced. It is done.
In Comparative Example 3, since the opening end of the open hole was not covered, it is considered that the binder component entered and filled in the open hole.
From the above results, it was found that by subjecting the porous oxide particles to water adsorption treatment, the binder component can be prevented from entering the open pores and the pores can be maintained.

  The surface-coated porous oxide particles of the present invention are formed by sealing the open ends of the open pores of the porous oxide particles with a coating layer made of an organic polymer, and making the open pores hydrophilic. It is possible to prevent binder components such as dispersants and resins from entering into the open pores and maintain the properties as porous oxide particles such as low refractive index and low dielectric property. The present invention can be applied to various optical parts that are required to have a low refractive index, a low dielectric property, etc. as well as an optical film such as a prevention film, a retardation film, and a diffusion film, and its industrial effect is great.

It is a process figure showing the surface covering method of porous oxide particles of a 1st embodiment of the present invention. It is process drawing which shows the surface coating method of the porous oxide particle of the 2nd Embodiment of this invention. It is a scanning electron microscope (SEM) image which shows the surface covering porous oxide particle of Example 1 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Porous oxide particle 2 Outer peripheral surface 3 Open hole 4 Volatile solvent 5 Reaction point 6 Coating layer

Claims (16)

A surface-coated porous oxide particle formed by covering a surface of a porous oxide particle in which a large number of pores are formed at least in the vicinity of the surface, and these pores are open pores having an open end on the surface. There,
The surface-coated porous oxide particles, wherein the open ends are sealed with a coating layer made of an organic polymer, and the inside of the open holes is made hydrophilic.   The surface-coated porous oxide particles according to claim 1, wherein the coating layer is fixed by being bonded to at least a part of an outer peripheral surface of the porous oxide particles.   The surface-coated porous oxide particles according to claim 1 or 2, wherein the coating layer has a thickness of 0.1 nm or more and 30 nm or less.   The average particle diameter of the porous oxide particles is 0.01 µm or more and 10 µm or less, and the diameter of the open end is 0.1 nm or more and 50 nm or less. The surface-coated porous oxide particles according to Item.   5. The porous oxide particles are mainly composed of one or more selected from the group consisting of silicon oxide, aluminum silicate, aluminum oxide, zirconium oxide, and titanium oxide. The surface-coated porous oxide particles according to any one of the above.   The surface-coated porous oxide particles according to any one of claims 1 to 5, wherein a volatile solvent having hydrophilicity is contained in the open pores.   The surface-coated porous oxide particles according to claim 6, wherein the volatile solvent is water. A method of covering a surface of a porous oxide particle in which a large number of pores are formed at least in the vicinity of the surface, and these pores are open pores having an open end on the surface,
A first step of adsorbing a volatile solvent having hydrophilicity in the open hole;
A second step of forming reaction points on the outer peripheral surface of the porous oxide particles;
A coating layer made of an organic polymer is bonded and fixed to at least a part of the outer peripheral surface of the porous oxide particle, and the opening end is sealed with the coating layer, and the volatilization in the open hole is performed. And a third step of removing the conductive solvent.   The method for coating a surface of porous oxide particles according to claim 8, wherein the second and third steps are performed in a solvent that is incompatible with the volatile solvent. A method of covering a surface of a porous oxide particle in which a large number of pores are formed at least in the vicinity of the surface, and these pores are open pores having an open end on the surface,
A first step of adsorbing a volatile solvent having hydrophilicity in the open hole;
A second step of forming reaction points on the outer peripheral surface of the porous oxide particles;
A third step of drying the porous oxide particles to remove the volatile solvent in the open pores;
A fourth step of bonding and fixing an organic polymer coating layer to at least a part of the outer peripheral surface of the porous oxide particles, and sealing the opening end with the coating layer;
A method for covering the surface of porous oxide particles, comprising:   The method for coating a surface of porous oxide particles according to claim 10, wherein the second and fourth steps are performed in a solvent that is incompatible with the volatile solvent.   The method for coating a surface of porous oxide particles according to any one of claims 8 to 11, wherein the organic polymer is insoluble in the volatile solvent.   The method for coating a surface of porous oxide particles according to any one of claims 8 to 12, wherein a thickness of the coating layer is 0.1 nm or more and 30 nm or less.   The average particle diameter of the porous oxide particles is 0.01 μm or more and 10 μm or less, and the diameter of the open end is 0.1 nm or more and 50 nm or less. A method for covering the surface of the porous oxide particles according to Item.   15. The porous oxide particles are mainly composed of one or more selected from the group consisting of silicon oxide, aluminum silicate, aluminum oxide, zirconium oxide, and titanium oxide. The surface coating method of the porous oxide particle of any one of these.   The method for coating a surface of porous oxide particles according to claim 8, wherein the volatile solvent is water.

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