JP2020142432A - Laminate - Google Patents

Abstract

To provide a laminate which is usable as a transparent substrate for protection of an optical element, in which the laminate has a self-cleaning function of easily removing oil stain by rainwater or water washing, easily recovering hydrophilicity, and maintaining hydrophilicity for an extended period.SOLUTION: The laminate is obtained by lamination of a hydrophilic resin layer containing a tetrafluoroethylene resin having a sulfonic acid group on a side chain and a binder resin and a substrate, where the laminate is characterized by that haze value of the substrate is 0.2% or less and the difference between the haze value of the laminate and the haze value of the substrate is 1% or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminate having a self-cleaning function against oil stains.

Generally, as an antifouling technique, it is desirable to impart hydrophilicity to the substrate so that the adhered dirt can be easily removed by rainwater or washing with water.
A technique has been proposed in which dirt adhering to the outer wall of a building can be removed by rainfall or injection of shower water (see, for example, Patent Document 1).
Patent Document 1 describes a coating material made of Nafion (registered trademark), which is a graft polymer composed of repeating units of a polymer tetrafluoroethylene having a perfluorosulfonic acid group in the side chain. It is described that by applying the paint to the outer wall, the coated surface exhibits superhydrophilicity for a long period of time.
Further, it is described in Cited Document 2 that a paint composed of a metal oxide having a photocatalytic function and the above-mentioned Nafion (registered trademark) is applied to a steel plate and a tent.

On the other hand, in recent years, the installation of security cameras and surveillance cameras has been increasing regardless of whether they are outdoors or indoors. From the viewpoint of reducing maintenance, it is preferable that the transparent substrate, which is a transparent cover that protects the optical elements of these security cameras and surveillance cameras, is a substrate that allows dirt adhering to the transparent substrate to be easily removed by rainwater or washing with water. In particular, maintenance opportunities may be limited depending on the installation location of security cameras and surveillance cameras. Therefore, the transparent substrate that protects the optical element has a self-cleaning function that removes any dirt that has adhered to it when water droplets fall due to rainwater or washing with water. Is desirable. In particular, from a practical point of view, it is desired that the transparent substrate that protects the optical element is a transparent substrate having a self-cleaning function against oil stains.

Japanese Unexamined Patent Publication No. 2006-45370 Japanese Unexamined Patent Publication No. 2006-233073

However, Patent Documents 1 and 2 do not have a specific description about stains that can be removed by rainfall or shower water injection, and only stains about rain streaks are described in the background technology column of Patent Document 2. Is.
The above-mentioned Patent Documents 1 and 2 do not describe whether or not the dirt can be easily removed by rainwater or washing with water and the hydrophilicity can be restored when the oil adheres.
The techniques described in Patent Documents 1 and 2 are sufficiently satisfactory from the viewpoint of providing a transparent substrate exhibiting a self-cleaning function that can easily remove stains by rainwater or washing with water for any stains including oil stains. It was not a good thing, and there was room for improvement.

Therefore, the present invention is a laminate that can be used as a transparent substrate for protecting an optical element, and exhibits a self-cleaning function that can easily remove oil stains by washing with rainwater or water and easily restore hydrophilicity. Furthermore, it is an object of the present invention to provide a laminate capable of stably maintaining hydrophilicity for a long period of time.

As a result of intensive research to solve the above problems, the present inventors have conducted a hydrophilic resin layer composed of a tetrafluorinated ethylene resin having a sulfonic acid group in the side chain and a binder resin, and a laminate having a base material. A laminate in which the haze value of the base material is equal to or less than a specific value and the difference between the haze value of the laminated body and the haze value of the base material is equal to or less than a specific value can solve the above-mentioned problems. The present invention has been completed.
That is, the present invention includes the following aspects.

According to the invention of claim 1,
A laminate formed by laminating a hydrophilic resin layer containing a tetrafluorinated ethylene resin having a sulfonic acid group in a side chain and a binder resin, and a base material.
Provided is a laminate characterized in that the haze value of the substrate is 0.2% or less, and the difference between the haze value of the laminate and the haze value of the substrate is 1% or less.

As a result, it is a laminate that can be used as a transparent substrate that protects optical elements, and it can easily remove oil stains by washing with rainwater or water, and exhibits a self-cleaning function that can easily restore hydrophilicity. It is possible to provide a laminate that can stably maintain its properties for a long period of time.

According to the invention of claim 2.
The laminate according to claim 1, wherein the binder resin is at least one resin selected from urethane acrylic resin, vinylidene fluoride copolymer, acrylic resin, fluororesin emulsion, and self-crosslinking polyester resin. Provided.

This makes it possible to select a binder resin that is compatible with the ethylene tetrafluoride resin having the sulfonic acid group in the side chain and easily bonds with the surface of the base material, and can obtain a specific haze value specified in the present invention. The indicated laminate can be obtained more reliably.

According to the invention of claim 3,
The laminate according to claim 1 or 2, wherein the hydrophilic resin layer contains particles of SiO ₂ is provided.

Thereby, the hydrophilic function of the surface of the hydrophilic resin layer can be further enhanced.

According to the present invention, it is a laminate that can be used as a transparent substrate for protecting an optical element, and exhibits a self-cleaning function that can easily remove oil stains by washing with rainwater or water and easily restore hydrophilicity. Further, it is possible to provide a laminate capable of stably maintaining hydrophilicity for a long period of time.

It is the schematic sectional drawing which shows one aspect of the layer structure of the laminated body of this invention. It is the schematic sectional drawing which shows the other aspect of the layer structure of the laminated body of this invention. It is a figure which shows the relationship between the change amount Δ (°) of the contact angle in Test Example 1 and the haze value of a laminated body. It is a figure which shows the relationship between the change amount Δ (°) of the contact angle in Test Example 1 and the haze value of a laminated body. It is a schematic diagram of the photoelectron spectrum obtained by analyzing the surface of the sample 5 of Test Example 1 by the XPS method (X-ray photoelectron spectroscopy). It is the schematic of the photoelectron spectrum obtained by analyzing the surface of the sample 9 of Test Example 1 by the XPS method (X-ray photoelectron spectroscopy). It is a schematic diagram of the photoelectron spectrum obtained by analyzing the surface of the sample 10 of Test Example 1 by the XPS method (X-ray photoelectron spectroscopy). It is a figure which shows the measurement result of the contact angle after the wear test in Example 6. It is a photograph of the surface of the laminate of Example 7 before the test. It is a photograph of the surface of the laminated body of Example 7 under test. It is a photograph of the surface of the laminated body of Example 7 after the test. It is a photograph of the surface of the laminate of Example 7 after the test and after watering.

Hereinafter, the laminate of the present invention will be described in detail, but the description of the constituent requirements described below is an example as an embodiment of the present invention, and is not specified in these contents.

(Laminate)
The laminate of the present invention is formed by laminating a hydrophilic resin layer and a base material.
The hydrophilic resin layer contains a tetrafluoroethylene resin having a sulfonic acid group in the side chain and a binder resin.
In the laminated body of the present invention, the haze value of the base material is 0.2% or less, and the difference between the haze value of the laminated body of the present invention and the haze value of the base material (hereinafter, "laminated body" in the present specification. The "difference between the haze value of the base material and the haze value of the base material" is also referred to as "the haze value in which the hydrophilic resin layer is involved") is 1% or less.
FIG. 1 shows a schematic view of the layer structure of the laminated body according to one aspect of the present invention.
As shown in FIG. 1, the laminated body 1 of one aspect of the present invention is formed by laminating a hydrophilic resin layer 2 and a base material 3. The hydrophilic resin layer 2 contains a tetrafluorinated ethylene resin 4 having a sulfonic acid group in the side chain and a binder resin 5.

<Hydrophilic resin layer>
The hydrophilic resin layer contains a tetrafluoroethylene resin having a sulfonic acid group in the side chain and a binder resin. Further, if necessary, other components may be contained.

<< Ethylene tetrafluoride resin having a sulfonic acid group in the side chain >>
The tetrafluoroethylene resin having a sulfonic acid group in the side chain (hereinafter, in the present specification, the "tetrafluoroethylene resin having a sulfonic acid group in the side chain" is also referred to as a "fluorine-based ionomer resin"). For example, the tetrafluorinated ethylene resin obtained by graft-polymerizing perfluorosulfonic acid described in Patent Document 1 (Japanese Unexamined Patent Publication No. 2006-45370) can be used.
Specific examples thereof include a tetrafluoroethylene resin obtained by graft-polymerizing a perfluorosulfonic acid having a sulfonic acid group at the end, which is represented by the following formula (1).

In the above formula (1), Rf is a perfluoroalkyl group, with SO ₃ H sulfonic acid group, x, y are integers.

Examples of the perfluoroalkyl group of Rf include a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms. A part of the carbon atom of the perfluoroalkyl group may be substituted with an oxygen atom.
As the perfluoroalkyl group of Rf, for example, a perfluoroalkyl group represented by the following formula (2), formula (3) or formula (4) is preferably mentioned.

The content of the fluorine-based ionomer resin in the hydrophilic resin layer is not particularly limited as long as a laminate showing a specific haze value specified in the present invention can be formed, and can be appropriately selected depending on the intended purpose. 8 to 30% is preferable, 10 to 30% is more preferable, and 10 to 25% is further preferable.

<< Binder resin >>
As the binder resin constituting the hydrophilic resin layer, the type of the binder resin is not particularly limited as long as a laminate showing a specific haze value specified in the present invention can be formed, and can be appropriately selected depending on the intended purpose. However, from the viewpoint of reducing the haze value of the hydrophilic resin layer and from the viewpoint of durability and abrasion resistance, the following resins are preferable.
A binder that is compatible with the above-mentioned fluorine-based ionomer resin (when the hydrophilic resin layer also contains the following other components, it is preferable that the hydrophilic resin layer also has good compatibility with the other components) and easily bonds with the surface of the base material. It is preferably a resin.
Therefore, as the binder resin according to the present invention, for example, at least one resin selected from urethane acrylic resin, vinylidene fluoride copolymer, acrylic resin, fluororesin emulsion, and self-crosslinking polyester resin is preferably mentioned. Be done.
The urethane acrylic resin, vinylidene fluoride copolymer, acrylic resin, fluororesin emulsion, and self-crosslinking polyester resin may be used alone or in combination of a plurality of resins selected from these resins. , Either is fine. For example, as the binder resin, a mixture composed of a fluororesin emulsion and a self-crosslinking polyester resin can be used.
When the binder resin according to the present invention is these resins, the haze value involving the hydrophilic resin layer and the haze value of the laminate can be reduced, and the laminate showing a desired haze value can be obtained more reliably. ..
Among them, urethane acrylic resin is more preferable as the binder resin.

<< Other ingredients >>
In addition to the fluorine-based ionomer resin and the binder resin, the hydrophilic resin layer according to the present invention contains various particles such as a photocatalyst such as silicon dioxide (SiO ₂ ) and titanium oxide, if necessary. May be good.
In the present invention, it is preferable that the hydrophilic resin layer contains nanoparticles of SiO ₂ . By containing the particles of SiO ₂ , the hydrophilicity of the surface of the hydrophilic resin layer can be further enhanced.
FIG. 2 shows a schematic view of the layer structure of the laminate of the present invention when the hydrophilic resin layer contains particles of SiO ₂ .
Laminate 1 of the present invention when containing the SiO ₂ particles in the hydrophilic resin layer, as shown in FIG. 2, in the hydrophilic resin layer 2, which contains particles 6 of SiO _2. In FIG. 2, the same components as those in FIG. 1 are designated by the same reference numerals.
The particle size and content of the SiO ₂ particles contained in the hydrophilic resin layer are not particularly limited as long as a laminate showing a specific haze value specified in the present invention can be formed, and can be appropriately selected.
The particle size of the particles of SiO ₂ is preferably 80 nm or less, more preferably 50 nm or less, still more preferably 15 nm or less, for example, from the viewpoint of preventing light scattering. Further, for example, from the viewpoint of preventing particle aggregation, 5 nm or more is preferable, and 10 nm or more is more preferable.
The content of the SiO ₂ particles in the hydrophilic resin layer is preferably 50% by mass or less, for example, from the viewpoint of preventing light scattering. Further, for example, from the viewpoint of ensuring the effect, 10% by mass or more is preferable.

In the present invention, it is more preferable that the hydrophilic resin layer does not contain a photocatalyst such as titanium oxide. This is because a laminated body having higher transparency can be obtained and a laminated body satisfying the requirement of a haze value of 1% or less can be more reliably produced when the photocatalyst is not contained.
In addition, when trying to achieve an antifouling effect by decomposing oil stains by using a photocatalytic reaction with a photocatalyst such as titanium oxide, there is usually a limitation that a sufficient antifouling effect cannot be expected in a place where it is difficult to be exposed to light. .. However, in the case where the hydrophilic resin layer does not contain the photocatalyst, the usable area of the laminated body can be expanded without worrying about the light source.

<< Method of forming a hydrophilic resin layer >>
When the fluorine-based ionomer resin, the binder resin, and other components are contained, the other components are mixed to prepare a resin composition (coating material).
The coating material may appropriately contain a solvent.
The solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include an organic solvent and a mixture of an organic solvent and water. Examples of the organic solvent include methanol, ethanol, isopropyl alcohol, ethylene glycol, propylene glycol monomethyl ether, dipropylene glycol-n-butyl ether, 2-butoxyethanol, methoxypropanol, methyl ethyl ketone, acetone, ethyl acetate, butyl acetate, toluene, and the like. Examples thereof include dimethylformamide, acetonitrile, methyl isobutyl ketone, and the like.
A hydrophilic resin layer can be formed by applying a coating material on a base material and drying the coating layer.
When the coating material contains an organic solvent, it is preferable to dry the coating layer by heating the coating layer and evaporating the organic solvent in the coating material.
The coating method is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include solution coating methods such as dip coating, spin coating, spray coating, roll coating and bar coating.
The conditions for heating and drying the coating layer are not particularly limited and may be appropriately selected. Examples thereof include conditions for heating and drying at 80 to 130 ° C. for 5 to 30 minutes.
As a more specific method for forming the hydrophilic resin layer, for example, a coating material containing a fluorine-based ionomer resin and a binder resin is coated on a base material using a bar coater, and the coating layer is heated to a temperature of 120 ° C. A method of forming a hydrophilic resin layer by heating and drying for 20 minutes can be mentioned.

<< Film thickness of hydrophilic resin layer >>
The thickness of the hydrophilic resin layer is not particularly limited as long as a laminate showing a specific haze value specified in the present invention can be formed, and can be appropriately selected. However, the thicker the thickness, the higher the haze value. In order to reduce the haze value in which the hydrophilic resin layer specified in the present invention is involved to 1% or less, the thickness of the hydrophilic resin layer is preferably thin.
Further, depending on the viscosity of the coating material, if the film thickness of the coating material at the time of coating is thick, problems due to sagging are likely to occur. Therefore, the film thickness of the hydrophilic resin layer is preferably set to be 5 μm or less in terms of the film thickness when dried.
On the other hand, since the fluorine-based ionomer resin seems to be colloidally aggregated in the solvent, if the thickness of the hydrophilic resin layer is too thin, it is difficult to obtain a smooth surface.
Further, in case of incorporating a SiO ₂ particles in a hydrophilic resin layer, sometimes particles of SiO ₂ also form secondary particles due to aggregation. Therefore, the film thickness of the hydrophilic resin layer is preferably 100 nm or more.
From the above, the thickness of the hydrophilic resin layer is preferably 100 nm to 5 μm, more preferably 2 to 5 μm, and even more preferably 3 to 5 μm.

<Base material>
As the base material constituting the laminate of the present invention, a base material showing a haze value of 0.2% or less is used.
As the base material, the type of the base material is not particularly limited as long as a laminate showing a specific haze value specified in the present invention can be formed, and can be appropriately selected depending on the intended purpose.
Since the composition of the hydrophilic resin layer is a resin, it is preferable that the base material is also a resin from the viewpoint of adhesion.
Generally, when a substrate having low smoothness is used, the haze value of the laminate tends to be high. Therefore, for example, in order to obtain a laminate having a desired haze value specified in the present invention, the base material may be selected from resins such as polycarbonate resin, polyacrylic resin, polyolefin resin, cyclic olefin resin, and polyester resin. preferable. Among them, acrylic resin is more preferably used as a base material from the viewpoint of transparency and cost, and polycarbonate resin is more preferably used as a base material from the viewpoint of strength and cost.

The shape of the base material is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a flat plate, a sheet, a film, or a material having a three-dimensional shape on the entire surface or a part thereof, or on the entire surface. Alternatively, it can have an arbitrary shape according to the purpose, such as one having a partial curvature.

When the base material is a film, examples of the molding method include an extrusion method, a cast molding method, a T-die method, a cutting method, and an inflation method. For these films, a plastic molded product formed by forming a single layer or a multilayer film can also be used as a base material.
The thickness of the base material is not particularly limited and can be appropriately selected depending on the intended purpose.

The haze value of the base material is 0.2% or less as described above, but from the viewpoint of surely forming a laminate showing a specific haze value specified in the present invention, the haze value of the base material is 0. It is preferably .15% or less, and more preferably 0.13% or less.

Various surface treatments may be applied to the surface of the base material in order to improve the coatability of the hydrophilic resin layer and the adhesiveness with the hydrophilic resin layer. Examples of the surface treatment include ozone treatment, plasma treatment, corona treatment, and silane coupling treatment.
The type of the base material is preferably resin, but for example, if a silane coupling agent is used as the base layer, a glass base material can also be used.

<Haze value (%)>
The difference between the haze value of the laminate of the present invention and the haze value of the base material (the haze value in which the hydrophilic resin layer is involved) is 1% or less.
Further, it is more preferable that the haze value of the laminate of the present invention is 1% or less.
The haze value (degree of cloudiness) is an index showing the degree of transparency, and is a value obtained by determining the ratio of diffused light to total transmitted light.
The haze value can be measured according to JIS K7136 using a C light source.

In the fluorine-based ionomer resin constituting the hydrophilic resin layer, since the sulfonic acid (-SO 3 _H) portion of the side chain is bonded to bonded carbon elemental greater elemental fluorine electronegativity of fluorine element Sulfonic acid also tends to be -SO ₃ ^- H ⁺ due to the interaction with the large electron attraction. Since the sulfonic acid portion of the side chain is strongly ionized, highly polar water molecules are easily attracted, and in the above-mentioned fluoroionic ionomer resin, the sulfonic acid portion of the side chain exhibits hydrophilicity.
On the other hand, the tetrafluorinated ethylene resin itself exhibits hydrophobicity. Therefore, the tetrafluoroethylene resin having a sulfonic acid group in the side chain has both hydrophobicity and hydrophilicity. For example, when the static wettability is measured, the Teflon skeleton has a high influence and shows hydrophobicity, but when the dynamic wettability such as a large droplet or dropping a droplet is measured, shows hydrophilicity due to the influence of -SO ₃ H present partially.
Therefore, it behaves differently from a general hydrophilic surface.
Therefore, when the present inventors studied oil stains, the oil stains on the surface of the hydrophilic resin may not be removed even when scrubbed in running water, and the hydrophilicity may not be restored, which is the haze value. It was confirmed that it affected.
The present inventors further investigated the haze value in which the hydrophilic resin layer is involved, and by extension, the haze value of the laminate, and in order to remove oil stains and restore hydrophilicity, the surface composition of the hydrophilic resin layer is involved. However, if it depends on the haze value of the laminate and the difference between the haze value of the laminate and the haze value of the base material (the haze value involving the hydrophilic resin layer) is 1% or less, oil stains On the other hand, it was found that hydrophilicity can be easily restored and maintained.
The significance of the haze value defined in the present invention will be clarified by the following Test Examples 1 and 2.

[Test Example 1]
A hydrophilic resin layer containing a tetrafluorinated ethylene resin having a sulfonic acid group in the side chain and a binder resin was formed on the substrate.
As shown in Table 1 below, Samples 1 to 11 having different compositions of the hydrophilic resin layers were prepared.
In Table 1, the tetrafluorinated ethylene resin (fluorine-based ionomer resin) having a sulfonic acid group in the side chain is a fluorine-based ionomer resin (manufactured by Daikin Industries, Ltd.) having the formula (3) as Rf of the formula (1). Using.

In sample 1, the hydrophilic resin layer contains 10% by mass of the fluorine-based ionomer resin (the content of the fluorine-based ionomer resin in the other samples is as shown in Table 1).
In Sample 1, a fluororesin emulsion (manufactured by Daikin Industries, Ltd.) was used as the binder resin (the same fluororesin emulsion as in Sample 1 was also used in the other samples 2 to 8).
In sample 2, 30% by mass of SiO ₂ particles are contained in the hydrophilic resin layer (the content of SiO ₂ particles or TiO ₂ particles in the other samples is as shown in Table 1). ..
As the SiO ₂ particles in each sample, Nissan Chemical Industries, Ltd. silica sol IPA-ST-L (particle diameter: 40 to 50 nm) was used in Samples 2 to 5, and Nissan Chemical Industries, Ltd. silica sol was used in Sample 9. IPA-ST (particle size: 12 nm) was used.
As the TiO ₂ particles in each sample, those manufactured by Ishihara Sangyo Co., Ltd. (particle diameter: 5 to 15 nm) were used.
In sample 9, urethane acrylic resin (manufactured by DSM Co., Ltd.) was used as the binder resin (the same urethane acrylic resin as in sample 9 was used in other samples 10).
In Sample 11, a mixture consisting of a fluororesin emulsion (manufactured by Daikin Industries, Ltd.) and a self-crosslinking polyester resin (manufactured by Unitica Co., Ltd.) was used as the binder resin.
As the base material, a polycarbonate base material (ECW100 t = 3 (thickness 3 mm) 10 cm square manufactured by Sumitomo Bakelite Co., Ltd.) was used. The haze value of the polycarbonate substrate was 0.13%.

Each component constituting the hydrophilic resin layer was mixed at the ratio shown in Table 1, and a solvent was further mixed to prepare a coating material.
In Samples 1 to 8, isopropyl alcohol, 2-butoxyethanol, and water were used as solvents.
In Samples 9 to 10, isopropyl alcohol and water were used as solvents.
In Sample 11, isopropyl alcohol, water, and dipropylene glycol-n-butyl ether were used as the solvent.
A coating material was applied to a polycarbonate base material with a bar coater # 10 and dried at a temperature of 120 ° C. for 20 minutes to obtain a laminate in which a hydrophilic resin layer was laminated on the base material.
The thickness of the hydrophilic resin layer before drying was 20 μm, and the film thickness after drying was 5 μm.

Gear oil was dropped on the surface of the hydrophilic resin layer for each sample, left for 1 hour, and then washed with water while gently rubbing with a Bencot.
The contact angle (°) before dropping the gear oil and the contact angle (°) after washing the gear oil with water (after washing) were measured with respect to the surface of the hydrophilic resin layer in the laminated body of each sample. Then, the amount of change Δ (°) between the contact angle before dropping the gear oil and the contact angle after cleaning was determined.
Here, the contact angle (°) is such that 10 μL of water droplets are dropped on the sample surface from a height of 10 cm, and the angle formed by the water droplets formed on the sample and the sample surface is the contact angle manufactured by Kyowa Interface Science Co., Ltd. The measurement was performed using the multifunctional integrated analysis software FAMAS installed in the meter.
The constituents and contents of the hydrophilic resin layer in each sample are shown in Table 1 below. Further, the haze value (%) of the laminated body, the contact angle (°) before dropping the gear oil on the laminated body, the contact angle (°) after cleaning, and the change amount Δ (°) of the contact angle. The results of each of the above are shown in Table 1 below.
Further, FIGS. 3 and 4 show the relationship between the change amount Δ (°) of the contact angle before dropping the gear oil and the contact angle after cleaning and the haze value of the laminated body.

From the results of Tables 1, 3 and 4, it was found that the degree of recovery of hydrophilicity of the laminate against oil stains differs depending on whether or not the haze value specified in the present invention is 1% or less. It was shown that the laminate in which the amount of change Δ (°) between the contact angle before dropping the gear oil and the contact angle after cleaning is 20 or less, more preferably 10 or less, can easily remove oil stains by rainwater or washing with water. There is. Therefore, in order to obtain a laminate that can easily remove oil stains by rainwater or washing with water, exhibit a self-cleaning function that can easily restore hydrophilicity, and maintain hydrophilicity stably for a long period of time, the laminate is 0. . A laminated body having a base material showing a haze value of 2% or less and having a difference between the haze value of the laminated body and the haze value of the base material (haze value involving a hydrophilic resin layer) of 1% or less. It is necessary to be.
In order to obtain a laminate satisfying the self-cleaning function against oil stains, the present inventors reduce the haze value and the haze value specified in the present invention is equal to or less than a predetermined value, that is, a haze involving a hydrophilic resin layer. It was confirmed that it is important to obtain a laminate having a haze value of 1% or less.
As shown in FIGS. 3 and 4, there is a correlation between the self-cleaning effect on oil stains and the haze value related to the laminate. On the other hand, the present inventors have confirmed that the self-cleaning effect on oil stains does not depend on the components constituting the hydrophilic resin layer or the surface composition of the hydrophilic resin layer.
Therefore, Test Example 2 below shows that the self-cleaning effect on oil stains does not depend on the components constituting the hydrophilic resin layer or the surface composition of the hydrophilic resin layer.

[Test Example 2]
The surface compositions of the samples 5, 9 and 10 prepared in Test Example 1 were analyzed.
Each sample was cut into about 1 × 2 cm with an ultrasonic cutter, and the types of elements present on the outermost surface (10 nm) were analyzed by the XPS method (X-ray Photoelectron Spectroscopy).
Schematic diagrams of the photoelectron spectra obtained by analyzing the surfaces of samples 5, 9 and 10 of Test Example 1 by the XPS method (X-ray photoelectron spectroscopy) are shown in FIGS. 5 to 7, respectively. In addition, the composition of the outermost surfaces of Samples 5, 9 and 10 of Test Example 1 is shown in Table 2 below.

According to the results of Tables 1 and 2, the types and ratios of the elements on the outermost surface of the hydrophilic resin layer are almost the same in Samples 5 and 9, although the constituent components forming the hydrophilic resin layer are different. Shown. On the other hand, the surface composition of the hydrophilic resin layer of the sample 10 is significantly different from that of the other samples 5 and 9.
As for the self-cleaning effect, as shown in the results of Table 1, the self-cleaning effect is observed in the samples 9 and 10, but the self-cleaning effect is not observed in the sample 5.
That is, from the results of Tables 1 and 2, it was found that the expression of the self-cleaning effect is more strongly influenced by the haze value than the surface composition of the hydrophilic resin layer. Then, it was confirmed that even if the surface composition of the hydrophilic resin layer is different, the laminated body can exhibit the self-cleaning effect as long as the laminated body has a haze value of 1% or less specified in the present invention.

As described above, the laminate having a haze value of 1% or less in which the hydrophilic resin layer is involved can easily remove the oil stains by rainwater or washing with water even if the oil stains adhere to the laminate, and the hydrophilicity can be easily restored. It is a laminated body that shows a cleaning function.
Among the laminated bodies in which the hydrophilic resin layer and the base material are laminated, the mechanism by which the hydrophilicity can be easily restored against oil stains by using the laminated body in which the haze value involving the hydrophilic resin layer is 1% or less is Although it is unknown, the present inventors think as follows.
On a surface with a high haze value (low smoothness), when oil adheres to micropores in which hydrophobicity is dominant, it is less likely to be affected by washing with water, whereas the haze value is low (high smoothness). Since the oil is not physically trapped on the surface, it is speculated that the oil will be washed away by washing with water.

In order to obtain a laminate showing a desired haze value, it is advisable to consider the type of binder resin, the content of fluorine-based ionomers, the thickness of the hydrophilic resin layer, and the like with respect to the hydrophilic resin layer. In case of containing particles such as SiO _2, as the aggregation of SiO ₂ particles does not occur, or the particle size and the content of SiO ₂ particles is taken into consideration. Further, in the hydrophilic resin layer, it is preferable to select a binder resin that does not agglomerate the components of the binder resin itself and has good compatibility with the fluorine-based ionomer and good adhesion to the base material. Also, it may be selected also good binder resin compatibility with the SiO ₂ particles in order not to agglomerate the SiO ₂ particles.
By considering each of the above factors, it is possible to reduce the influence of the light diffusing component in the hydrophilic resin layer on the haze value, and it is possible to obtain a smooth hydrophilic resin layer having a surface with few irregularities.
Further, if the surface of the base material has irregularities, the surface of the hydrophilic resin layer is also affected. Therefore, it is preferable to use a base material having a smooth surface with few irregularities. Further, the influence of the light diffusing component in the base material on the haze value may be reduced in consideration of the constituent components of the base material, the type thereof, the film thickness of the base material, and the like.
Each of these factors described above may be considered in order to obtain a laminate showing the desired haze value.

<Application of laminated body>
As shown in the above test example and the following examples, the laminate of the present invention exhibits a self-cleaning function capable of easily removing oil stains by washing with water and easily recovering hydrophilicity. Therefore, even in an environment where a large amount of oil or oil mist adheres, oil stains can be easily removed by washing with rainwater or water.
Further, as shown in the following examples, the laminate of the present invention has an effect that it is difficult for dust to adhere to it, and even if it adheres, it can be easily removed by washing with water. It is considered that this is because, as described above, due to the high ionization of the fluorine-based ionomer, the antistatic function is obtained, so that a surface on which dust does not easily adhere can be formed.
Therefore, the laminate of the present invention can be applied to products in various fields such as optical parts and design parts as a transparent protective substrate having a high barrier property against dust and oil stains. For example, a security camera or a surveillance camera It can be applied to a transparent cover or the like that protects an optical element such as.

The present invention will be described in more detail with reference to Examples below, but the scope of the present invention is not limited to these Examples.

(Example 1)
A laminate was formed by laminating a hydrophilic resin layer containing a tetrafluoroethylene resin (fluorine-based ionomer resin) having a sulfonic acid group in a side chain, a urethane acrylic resin, and SiO ₂ particles on a base material.
As the fluorine-based ionomer resin, a resin having the formula (3) as Rf of the formula (1) (manufactured by Daikin Industries, Ltd.) was used.
The urethane acrylic resin used was manufactured by DSM Co., Ltd.
As the SiO ₂ particles, silica sol IPA-ST (particle diameter: 12 nm) manufactured by Nissan Chemical Industries, Ltd. was used.
The content of the fluorine-based ionomer resin in the hydrophilic resin layer was 25% by mass.
The content of SiO ₂ particles in the hydrophilic resin layer was 40% by mass.

As the base material, a polycarbonate base material (ECW100 t = 3 (thickness 3 mm) 10 cm square manufactured by Sumitomo Bakelite Co., Ltd.) was used. The haze value of the polycarbonate substrate was 0.13.

A coating material was prepared by uniformly mixing 15 parts by mass of a fluorine-based ionomer resin, 14 parts by mass of a urethane acrylic resin, 20 parts by mass of SiO ₂ particles, and 45 parts by mass of a mixed solvent of isopropyl alcohol and water.
A coating material was applied to a polycarbonate base material with a bar coater # 10 and dried at a temperature of 120 ° C. for 20 minutes to obtain a laminate in which a hydrophilic resin layer was laminated on the base material.
The thickness of the hydrophilic resin layer before drying was 20 μm, and the film thickness after drying was 5 μm.

Gear oil was dropped on the surface of the hydrophilic resin layer, left for 1 hour, and then washed with water while gently rubbing with a Bencot.
The contact angle (°) before dropping the gear oil and the contact angle (°) after washing the gear oil with water (after washing) were measured with respect to the surface of the hydrophilic resin layer in the laminate. Then, the amount of change Δ (°) between the contact angle before dropping the gear oil and the contact angle after cleaning was determined.
Here, the contact angle (°) is such that 10 μL of water droplets are dropped from a height of 10 cm onto the surface of the hydrophilic resin layer in the laminate, and the water droplets formed on the hydrophilic resin layer and the surface of the hydrophilic resin layer are formed. The angle between the two was measured using FAMAS, a multifunctional integrated analysis software installed in a contact angle meter manufactured by Kyowa Interface Science Co., Ltd.

(Example 2)
In Example 1, the coating material was coated on the polycarbonate substrate with bar coater # 10, and the drying conditions for drying the coating material were changed to drying at a temperature of 120 ° C. for 10 minutes. The laminate of Example 2 was prepared in the same manner as in the example.
With respect to the laminate of Example 2, the contact angle (°) before dropping the gear oil and the contact angle (°) after washing with the gear oil (after washing) at the time of producing the laminate were measured in the same manner as in Example 1.

(Example 3)
A laminate of Example 3 was produced in the same manner as in Example 1 except that the SiO ₂ particles were not contained in Example 1.
With respect to the laminate of Example 3, the contact angle (°) before dropping the gear oil and the contact angle (°) after washing with the gear oil (after washing) at the time of producing the laminate were measured in the same manner as in Example 1.

(Comparative Example 1)
In Example 1, the type of the binder resin was changed to a fluororesin emulsion, the content of the fluorine-based ionomer was changed to 10% by mass, and the SiO ₂ particles (silica sol IPA-STL (particle size: 45 nm) manufactured by Nissan Chemical Industries, Ltd.) were prepared. A laminate of Comparative Example 1 was prepared in the same manner as in Example 1 except that the content was changed to 30% by mass.
In Comparative Example 1, the fluororesin emulsion used was manufactured by Daikin Industries, Ltd.
For the laminated body of Comparative Example 1, the contact angle (°) before dropping the gear oil and the contact angle (°) after washing with the gear oil (after washing) at the time of producing the laminated body were measured in the same manner as in Example 1.

(Comparative Example 2)
A laminate of Comparative Example 2 was produced in the same manner as in Comparative Example 1 except that the SiO ₂ particles were not contained in Comparative Example 1.
With respect to the laminated body of Comparative Example 2, the contact angle (°) before dropping the gear oil and the contact angle (°) after washing with the gear oil (after washing) at the time of producing the laminated body were measured in the same manner as in Example 1.

The haze value (%) of the laminated body in Examples 1 to 3 and Comparative Examples 1 and 2, the contact angle (°) before dropping and the contact angle (°) after washing when the gear oil was dropped on the laminated body. The results of the change in contact angle Δ (°) are shown in Table 3 below.

(Example 4)
The laminate prepared in Example 1 was stored for one year in a container installed indoors in which temperature and humidity were not controlled.
The following experiment was carried out on the laminated body of Example 1 after one year had passed.
First, the contact angle (°) was measured with respect to the laminated body of Example 1 one year after it was taken out of the container.
Next, the laminate of Example 1 after one year had passed was washed with water, gear oil was dropped on the surface of the hydrophilic resin layer, left for 1 hour, and then washed with water while being lightly rubbed with a bencot. The place where the gear oil was dropped was the same as the place marked in the gear oil dropping experiment one year ago.
Then, the contact angle (°) before dropping the gear oil after washing with water and the contact angle (°) after washing with water (after washing) of the gear oil were measured with respect to the surface of the hydrophilic resin layer in the laminated body after one year. .. Then, the amount of change Δ (°) between the contact angle before dropping the gear oil and the contact angle after cleaning was determined. Furthermore, the contact angle (°) (initial value contact angle) before dropping the gear oil at the time of preparing the laminate in the experiment conducted one year ago and the laminate after one year in the experiment conducted one year later. The amount of change Δ (°) with the contact angle after cleaning the gear oil was also determined.

(Example 5)
Similar to the laminate of Example 1 used in Example 4, the laminate prepared in Example 2 was also stored in the same container for one year.
With respect to the laminate of Example 2 after one year has passed, the contact angle (°) before dripping the gear oil after washing with water and the contact angle (° after washing) after washing with the gear oil (after washing) are performed in the same manner as in Example 4. ) Was measured respectively.

(Comparative Example 3)
Similar to the laminate of Example 1 used in Example 4, the laminate prepared in Comparative Example 1 was also stored in the same container for one year.
The contact angle (°) before dripping gear oil after washing with water and the contact angle (°) after washing with gear oil (after washing) with respect to the laminate of Comparative Example 1 after one year has passed, in the same manner as in Example 4. ) Was measured respectively.

(Comparative Example 4)
Similar to the laminate of Example 1 used in Example 4, the laminate prepared in Comparative Example 2 was also stored in the same container for one year.
The contact angle (°) before dripping gear oil after washing with water and the contact angle (°) after washing with gear oil (after washing) with respect to the laminate of Comparative Example 1 after one year has passed, in the same manner as in Example 4. ) Was measured respectively.

In Examples 4 to 5 and Comparative Examples 3 to 4, the contact angle (°) when taken out of the container after one year has passed, the contact angle (°) after washing with water (= before dropping gear oil), and washing with gear oil with water. Table 4 below shows the results of the subsequent (after cleaning) contact angle (°), the amount of change in the contact angle Δ (°), and the amount of change in the contact angle Δ (°) with the initial value at the time of fabrication. ..
Table 4 shows the contact angle (°) before dropping the gear oil, the contact angle (°) after cleaning the gear oil, and the change amount Δ (°) of the contact angle when the laminate was manufactured one year ago. Each result described in 3 is also described.

(Example 6)
The laminate of Example 6 was prepared in the same manner as in Example 1.
After conducting a wear experiment on the laminated body of Example 6 under the following test conditions, the contact angle (°) was measured in the same manner as in the method described in Example 1.
<Abrasion test conditions>
Testing machine: (Traverse wear testing machine)
Test conditions: Nell cloth, load 500 g / 4 cm ² , number of wears 500, 1000, 1500, 2000, 2500 reciprocations The measurement results of the contact angle (°) when the number of times of wear is 500, 1000, 1500, 2000, 2500 are shown in the figure. Shown in 8.

(Example 7)
In Example 1, the laminate of Example 7 was produced in the same manner as in Example 1 except that the base material was a dome-shaped polycarbonate base material and the method of applying the coating material on the base material was spray coating. did.
Eleven kinds of JIS test powder 1 (Kanto loam layer) were sprinkled on the dome cover with respect to the laminate of Example 7. The dome cover was then turned over to remove the sand. Furthermore, water was sprayed on the entire dome cover by spraying, and the dome cover was washed with water.
A photograph of the surface of the laminate of Example 7 before sprinkling sand (before the test) is shown in FIG. 9A, a photograph of the surface during the test of sprinkling sand is shown in FIG. 9B, and after the test, the dome. FIG. 9C shows a photograph of the surface after the cover was turned over to remove sand, and FIG. 9D shows a photograph of the surface after washing with water by spraying water.

As shown in Examples, the laminate of the present invention exhibits a self-cleaning function that can easily remove oil stains by washing with water and easily restore hydrophilicity, and further maintains hydrophilicity stably for a long period of time. I found that I could do it.
Further, as shown in FIG. 8, the laminate of the present invention showed a stable contact angle up to 2500 reciprocations, and was found to be excellent in wear resistance. As described above, the laminate of the present invention has excellent wear resistance, and the adhesion between the base material and the hydrophilic resin layer is also excellent.
Further, as shown in FIGS. 9A to 9D, it was found that the laminate of the present invention is difficult to adhere to dust, and even if it adheres, it can be easily removed by washing with water.

1 Laminate 2 Hydrophilic resin layer 3 Base material 4 Ethylene tetrafluoride resin having a sulfonic acid group in the side chain 5 Binder resin 6 Particles of SiO ₂

Claims (3)

A laminate formed by laminating a hydrophilic resin layer containing a tetrafluorinated ethylene resin having a sulfonic acid group in a side chain and a binder resin, and a base material.
A laminate characterized in that the haze value of the base material is 0.2% or less, and the difference between the haze value of the laminate and the haze value of the base material is 1% or less. The laminate according to claim 1, wherein the binder resin is at least one resin selected from a urethane acrylic resin, a vinylidene fluoride copolymer, an acrylic resin, a fluororesin emulsion, and a self-crosslinking polyester resin. The laminate according to claim 1 or 2, wherein the hydrophilic resin layer contains particles of SiO ₂ .