JP7213866B2 - Article with layer containing organic polymer with high affinity for sebum - Google Patents

Description

TECHNICAL FIELD The present invention relates to an article provided with a layer that facilitates coping with appearance deterioration due to adhesion of dirt, and more particularly to an article provided with a layer that facilitates coping with adhesion of sebum.

Adhesion of dirt is a factor that deteriorates the appearance of various articles, particularly articles having surfaces made of metal, plastic, ceramics, glass, or the like. Antifouling coatings are known means for addressing this problem. Antifouling coatings are often implemented by forming a membrane containing a fluorine-containing polymer. Fluoropolymers having oil repellency are sometimes used to prevent adhesion of oil-based dirt in addition to water-based dirt. Antifouling membranes containing fluorine-containing polymers are disclosed, for example, in US Pat.

JP 2014-196455 A JP 2014-196456 A

However, according to the studies of the present inventors, conventional antifouling films have room for improvement as a coating for dealing with dirt including sebum that adheres to the body due to contact with the human body. For example, sebum, which is observed as a transferred fingerprint, is difficult to prevent from adhering even with a film containing a fluorine-containing polymer. In addition, a film containing a fluorine-containing polymer does not necessarily make it possible to easily remove dirt containing sebum by wiping with a dry cloth or paper that is readily available.

SUMMARY OF THE INVENTION One of the objects of the present invention is to provide an article having a film on its surface suitable for suppressing or recovering appearance deterioration due to sebum adhesion.

As a result of intensive studies, the present inventors have found that the above object can be achieved by a completely different approach from conventional coatings that improve oil repellency to prevent dirt from adhering.

The present invention, as one form thereof,
comprising a substrate and a film formed on the substrate;
the membrane comprises a layer exposed on the surface of the membrane;
The surface roughness Ra of the surface is 0.5 nm to 50 nm,
The falling angle of water measured by dropping a water droplet with a mass of 4 mg on the surface is 30 degrees or less,
Provided is an article in which at least one of the following a) to c) is satisfied.
a) said layer comprises an organic polymer having a backbone comprising a polydialkylsiloxane structure;
b) said layer comprises an organic polymer, said organic polymer being free of perfluoroalkyl or perfluoroalkylene groups;
c) A contact angle of 15 degrees or more measured by dropping a droplet of oleic acid having a mass of 4 mg on the surface.
At least one of a) to c) may be established, and only one of them may be established, only any two of them may be established, or all of them may be established.

As another form of the present invention,
comprising a substrate and a film formed on the substrate;
the membrane comprises a layer exposed on the surface of the membrane;
The surface roughness Ra of the surface is 0.5 nm to 50 nm,
The layer provides an article comprising a polymeric brush of an organic polymer having a backbone comprising a polydialkylsiloxane structure.

The article described above has a film on its surface that is suitable for suppressing or recovering appearance deterioration due to adhesion of sebum from the human body. The surface of the article described above has a sufficiently low falling angle of water, and is also suitable for preventing contamination supplied from adhering droplets.

1 is a diagram schematically showing a polymer brush included in one embodiment of the present invention; FIG. FIG. 10 is a diagram showing the result of observing the surface of the film formed in Example 2 with a scanning electron microscope (SEM). FIG. 10 is a diagram showing the results of SEM observation of the surface of the film formed in Example 3; FIG. 10 is a diagram showing the result of observing the surface of the film formed in Example 3 with an atomic force microscope (AFM); FIG. 10 is a diagram showing the results of SEM observation of the surface of the film formed in Example 4; FIG. 10 is a diagram showing the results of AFM observation of the surface of the film formed in Example 4;

Embodiments of the present invention will be described below, but the following description is not intended to limit the present invention to specific embodiments.

In one form of the invention, an article comprises a substrate and a film formed on the substrate. The membrane includes a layer exposed on the surface of the membrane. This layer covers at least part of the surface of the article. The layer exposed on the surface of the membrane preferably contains an organic polymer. In this specification, a polymer whose main chain is a repeating unit of (—O—Si—) like a polydialkylsiloxane structure, as long as it contains an organic group (a side chain alkyl group in the polydialkylsiloxane structure), To be included in organic polymers.

(Base material)
The substrate typically has a surface composed of metal, plastic, ceramics or glass. The surface roughness Ra of this surface may be less than 2 nm, or even less than 1 nm. Sebum adhering to such a smooth surface locally diffuses the light incident on the surface, and its presence is likely to be visually recognized as dirt.

The substrate may be composed of at least one selected from metals, plastics, ceramics and glass. The substrate may be transparent or opaque. An example of the substrate is a transparent material having a visible light transmittance of 70% or more and a haze of 10% or less, such as plastic or glass. Another example of a substrate is a highly reflective material with a visible light reflectance of 70% or more, such as a metal with a mirror-polished surface or deposited as a smooth film. Sebum adhering to the surface of a base material having such a high transmittance or reflectance is easily visible and tends to affect the appearance. The shape of the substrate is not particularly limited, but the substrate is typically a shape having a pair of flat surfaces parallel to each other, that is, a plate. There are also no particular restrictions on the size and thickness of the substrate.

A glass plate is a typical plate material to which sebum adhesion is a problem. Glass sheets are used in architectural applications such as window glass and doors; furniture and shop decoration applications such as partitions and showcases; and industrial applications such as commercial refrigerators and touch panels. ing. One of the applications where this requirement is most apparent is smartphone cover glass. For this purpose, chemically strengthened glass sheets are often used.

(film)
The film formed on the substrate may be composed of a single layer or multiple layers. When the film is composed of a plurality of layers, layers other than the layer forming the surface of the film are hereinafter referred to as underlayers. The underlayer may be a single layer, or may be composed of a plurality of layers.

The surface roughness Ra of the film surface is preferably 0.5 nm or more, more preferably 0.7 nm or more, and may be 1 nm or more. Ra is preferably 50 nm or less, 40 nm or less, 30 nm or less, further 20 nm or less, particularly 15 nm or less, and may be 10 nm or less. If Ra is controlled to be small, it becomes easy to make the finger touching the surface feel smooth and to suppress glare in the appearance of the surface of the film. If this characteristic is important, Ra should be controlled to 12 nm or less, more preferably 10 nm or less, and particularly 8 nm or less. However, when Ra is less than 0.5 nm, it becomes difficult to make fingers feel smooth. As is well known, Ra means arithmetic mean roughness, and is specified in JIS B0601:2013 in Japanese Industrial Standards.

The surface of the film preferably has convex portions and flat portions. The convex portion may be surrounded by a flat portion. In this case, the flat portion may surround each of the protrusions or may surround a plurality of protrusions. With such a preferable surface, the influence of the deposition of fine dust on the surface roughness Ra is smaller than with a surface having concave portions instead of convex portions. Note that the flat portion need not be completely flat. In this specification, even if the surface height of the film locally varies within a range of ±0.8 nm, or even ±1 nm, the film thickness is considered to be “flat”.

The surface of the membrane may be substantially composed of convex portions and flat portions. However, even in this case, regions (usually concave portions) that cannot be regarded as convex portions or flat portions may exist in less than 5% of the surface of the film.

The shape of the convex portion is preferably dome-shaped. This preferred shape is advantageous in that it provides a smooth feel to the finger touching the surface. The shape and size of the convex portion can be measured by SEM observation. In this specification, the dome shape means that the cross-sectional profile passing through the apex becomes an upwardly convex curve in the part that can be observed from the direction perpendicular to the surface of the film, and 70% or more of the surface can be observed from the same direction. refers to the shape. The dome-shaped convex portion can be formed, for example, by filling the remainder of the lower part of the spherical fine particles with a binder so that the upper part of the spherical fine particle is exposed.

If the protrusions are too high, the feel of the finger touching the surface may be impaired. If this is important, the height of the convex portion is preferably 100 nm or less, more preferably 80 nm or less, particularly 60 nm or less, and may be 50 nm or less in some cases. The height of the protrusions is preferably 5 nm or more, particularly 8 nm or more. A perfectly non-planar surface is desirable to reduce the extent of sebum and other dirt adhesion.

The diameter of the projections is preferably 200 nm or less, more preferably 150 nm or less, particularly 120 nm or less, and may be 100 nm or less in some cases. The diameter of the convex portion is preferably 10 nm or more, particularly 20 nm or more. The diameter of the projection is determined by the diameter of a circle having the same area as the bottom of the film when observed from the direction perpendicular to the surface of the film. Also, the ratio of the height to the diameter of the convex portion is, for example, 10 to 85%, further 15 to 75%.

On the surface of the film, the ratio of the total area occupied by the convex portions to the area of the flat portions is preferably 15:85 to 80:20, more preferably 20:80 to 75:25, and in some cases 30:70 to 70. :30.

The underlayer preferably has a surface roughness Ra within a suitable range for the surface roughness Ra to be imparted to the surface of the film. According to this preferred embodiment, even if the layer containing the organic polymer is formed very thinly, a suitable Ra can be imparted to the surface of the film. The surface of the underlayer is also preferably composed of flat portions and convex portions. The preferable shape and size of the projections and the area ratio between the flat portion and the projections are as described above. For example, the surface of the underlayer preferably has a dome-shaped convex portion and a flat portion.

The underlayer preferably has a functional group on its surface that reacts with the functional group contained in the organic polymer to fix the organic polymer to the underlayer. The type of this functional group is not limited as long as it can react with the reactive functional group contained in the organic polymer. A hydroxy group may be present on the surface of the underlayer as a silanol group (Si—OH).

A metal oxide film formed by a sol-gel method has abundant hydroxy groups on its surface in the formed state, and is suitable for an underlayer. The metal atom constituting the metal oxide is preferably at least one selected from Si, Ti, Al, Zr, Ta, Nb, Nd, La, Ce and Sn, more preferably at least one selected from Si, Ti and Al. A particularly suitable metal oxide film is an oxide film of Si, that is, a silica film. For the sake of convenience, in this specification, an oxide of Si is treated as a metal oxide, and Si is treated as one type of metal atom in accordance with common practice.

A hydrolyzable metal compound represented by the following formula (1) is preferably used for forming a metal oxide film by the sol-gel method.
R _q MX _pq (1)
In formula (1), M is a metal atom, and preferred examples thereof are as described above. R is a hydrocarbon group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms. Preferred hydrocarbon groups are alkyl groups, especially linear alkyl groups. X is a hydrolyzable functional group or a halogen atom. The hydrolyzable functional group is preferably at least one selected from alkoxyl groups, acetoxy groups, alkenyloxy groups and amino groups. A preferred halogen atom is Cl. p is the valence of the metal atom and is 4 when M is Si. q is an integer of 0 or more and (p-1) or less. When M is Si, q is 0-3, preferably 0-2, more preferably 0 or 1.

The convex portion of the film may be derived from fine particles contained in the underlayer. Metal oxide fine particles are suitable for the fine particles. Preferred examples of the metal oxide that constitutes the metal oxide fine particles are as described above for the metal oxide film. Particularly preferred metal oxide fine particles are silica fine particles. The metal oxide fine particles may be introduced into the film by, for example, adding colloidal silica to the film-forming liquid by the sol-gel method. In this preferred embodiment, the metal oxide produced from the hydrolyzable metal compound serves as a binder for the metal oxide fine particles and constitutes the flat portion. The diameter of the metal oxide fine particles may be determined according to the target diameter and height of the projections, for example, it may be determined so as to match the target diameter of the projections. Fine particles preferably do not contain secondary particles in which primary particles are aggregated.

Subcomponents other than the metal oxide, such as an ultraviolet absorber, an infrared absorber, a colorant, and a silane coupling agent, may be added to the metal oxide film, if necessary. The silane coupling agent improves the adhesive strength between the plastic substrate and the underlying layer. In this specification, the metal oxide film is used as a term that refers to a film in which the metal oxide is the most abundant component on a mass basis, and hydrocarbons derived from organic subcomponents and hydrolyzable compounds Groups (R) are permissible. The silane coupling agent may be applied on the substrate as a primer layer before forming the metal oxide film.

(layer exposed on the surface of the membrane)
The layer exposed on the surface of the membrane preferably has at least one selected from the following features a) to c).
a) Contains an organic polymer having a backbone comprising a polydialkylsiloxane structure.
b) It contains an organic polymer, which organic polymer does not contain perfluoroalkyl or perfluoroalkylene groups.
c) It has a surface with a contact angle of 15 degrees or more when a droplet of oleic acid having a mass of 4 mg is dropped and measured.
This layer may have more than one of the above features, such as a) and b), a) and c), b) and c), or all of the above features a)-c).

The layer exposed on the surface of the membrane preferably comprises an organic polymer having at least one selected from the following characteristics i) to iv).
i) The Hansen total solubility parameter δ total is in the range of 10 to 20 MPa ^1/2 and/or the distance between coordinates with oleic acid in Hansen space is 8 MPa ^1/2 or less.
ii) have a backbone containing a polydialkylsiloxane structure;
iii) One end is fixed to an underlying layer or substrate included in the film separately from the layer containing the organic polymer, and the other end is exposed on the surface of the film.
iv) does not contain fluorine-containing groups such as perfluoroalkyl or perfluoroalkylene groups, as well as fluoroalkyl groups;

(About feature i))
The Hansen Solubility Parameter (HSP) is known as a parameter that describes the mutual solubility of substances. In HSP, the dispersion term dD indicating intermolecular dispersion force, the polarization term (polarity term) dP indicating intermolecular dipole interaction, and the hydrogen bonding term dH indicating intermolecular hydrogen bond Solubility is indicated. A combination of substances having a smaller distance between coordinates of HSPs in the Hansen space whose coordinate axes are the above three terms has a higher affinity and is more likely to be mutually dissolved.

Oleic acid is a representative fat that constitutes sebum. Sebum contains various components, but the component that is the main cause of deterioration in appearance is fat. Therefore, oleic acid is suitable as an evaluation criterion for affinity with sebum. Specifically, the distance in the Hansen space between the HSP of the organic polymer and the HSP of oleic acid (also referred to as the HSP distance) is preferably 7 MPa ^1/2 or less, more preferably 6 MPa ^1/2 or less, and even more preferably 5 MPa ¹ . It is preferable to select the organic polymer so that it becomes ^/2 or less.

As the organic polymer, those having a Hansen total solubility parameter δtotal in the range of 10 to 20 MPa ^1/2 are suitable. δtotal may be in the range of 12-19 MPa ^1/2 . For example, .delta.total of polydimethylsiloxane is about 15.1 MPa.sup.1 ^/2 , and .delta.total of oleic acid is about 18.0 ^MPa.sup.1 /2, which is close to the range.

An organic polymer with the above-mentioned solubility parameters and a high affinity for oleic acid can provide a layer surface that facilitates dealing with sebum stains.

(About feature ii))
The alkyl group constituting the polydialkylsiloxane structure preferably has 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, more preferably 1 or 2 carbon atoms. The alkyl group may be a linear or branched chain alkyl group or a cyclic alkyl group.

A backbone comprising a polydialkylsiloxane structure is preferably represented by formula (2).
—(Si(R ¹ )(R ² )—O—) _n — (2)
R ¹ and R ² are each directly bonded to Si. R ¹ and R ² are each independently an alkyl group having the above-mentioned number of carbon atoms (1-6, preferably 1-3, more preferably 1 or 2). n is a natural number in the range 3-2000, more preferably 4-1000, especially 5-750. Incidentally, the oxygen atom (--O--) in the formula (2) is partly a bond that can be formed by a reactive functional group described later, such as an ester bond (--C(=O)--O--), an amide It may be substituted with a bond (-C(=O)-N(-H)-) or the like.

An organic polymer having a polydialkylsiloxane structure in its main chain has an excellent affinity with the fat component of sebum. A notable property expressed by this affinity is sebum absorbability, in other words, sebum disappearance, exhibited by an organic polymer having a relatively small n, which indicates the degree of polymerization. For example, even if a human finger touches the surface of the sebum-dissipating film, it becomes difficult to see after at least a predetermined period of time has passed, and in some cases, it becomes completely invisible. Organic polymers with n between 3 and 50, especially between 4 and 20, especially between 5 and 10 are suitable for exhibiting fugitive properties.

An organic polymer having a polydialkylsiloxane structure with a high degree of polymerization is inferior to an organic polymer with a low degree of polymerization in sebum elimination properties, but exhibits practically sufficient sebum wiping properties. It has been thought that it is difficult to completely wipe off sebum with a dry cloth or paper. However, an organic polymer having a large degree of polymerization n, for example, an organic polymer having n of 50 to 1000, particularly 100 to 500, is suitable for erasing residual sebum by wiping with a dry cloth or the like to such an extent that it becomes invisible. ing.

One end of the organic polymer having a main chain containing a polydialkylsiloxane structure may be fixed to the underlying layer or substrate, and the other end may be exposed on the surface of the film. One end to be fixed is one end of the main chain, and the other end of the main chain is exposed on the surface of the membrane. The configuration in which one end is fixed can contribute to improving the durability of the layer containing the organic polymer.

A collection of side-by-side organic polymers with one end fixed and the other free end is sometimes called a polymer brush. A general purpose oil repellent film may include a polymer brush composed of groups of perfluoroalkyl chains. In contrast, polymer brushes that may be constructed in this embodiment may comprise linear polydialkylsiloxane chains.

(About feature iii))
An organic polymer with this feature can constitute a polymer brush, with one end anchored to an underlying layer or substrate and the other end exposed to the surface of the membrane. The surface of the polymer brush is suitable for improving sebum disappearance and wiping. In particular, flexible organic polymers that do not contain perfluoroalkyl groups that cause flexibility loss can form polymer brushes that are relatively flexible and have microscopically smooth surfaces.

(About feature iv))
An organic polymer containing a perfluoroalkyl or perfluoroalkylene group, particularly a perfluoroalkyl or perfluoroalkylene group having about 8 or more carbon atoms, contributes to high oil repellency. Fluorine-containing polymers of this type are of value as membranes to prevent adhesion of water-based soils and certain types of oil-based soils. The perfluoroalkyl group is a monovalent group represented by CF ₃ -(CF ₂ ) _r -, and the perfluoroalkylene group is a divalent group represented by -(CF ₂ ) _r+1 -. Here, r is an integer of 0 or more. However, fluorine-containing polymers with perfluoroalkyl or perfluoroalkylene groups are unsatisfactory in their ability to remove adhering sebum. This is thought to be related to the fact that perfluoroalkyl groups and the like exhibit high crystallinity especially when they are long.

Unlike conventional approaches to enhancing oil repellency, in this embodiment it is preferred to use organic polymers that do not contain per-fluoroalkyl or perfluoroalkylene groups, and even organic polymers that do not contain fluorine-containing groups. This organic polymer, as described above, may preferably have one end fixed to the underlying layer or substrate and the other end exposed to the surface of the membrane to form a flexible polymer brush. Flexible polymer brushes are considered suitable for absorption of sebum into membranes because their shafts easily bend. One of the main chains of the organic polymer suitable for constructing the flexible polymer brush is the polydialkylsiloxane structure described above, but the main chain of the organic polymer is not limited to that having the same structure.

For the sake of convenience, features i) to iv) have been separately described above, but the organic polymer may optionally have any of the features described in each section.

The layer exposed on the surface of the membrane may be a layer substantially composed of an organic polymer. As in the case described above, in this specification, substantially constituted does not mean that other ingredients are not allowed at all, but the total content of other ingredients is allowed in the range of less than 5% by mass. It is the intention to

Organic polymers can be formed, for example, using reactive functional group-containing polymers represented by formula (3).
Z ¹ Si(R ³ )(R ⁴ )—O—(Si(R ¹ )(R ² )—O—) _m —Si(R ⁵ )(R ⁶ )Z ² (3)
Each of R ¹ to R ⁶ is directly bonded to Si. R ¹ to R ⁶ are each independently an alkyl group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, more preferably 1 or 2 carbon atoms. The alkyl group may be a linear or branched chain alkyl group or a cyclic alkyl group. m is a natural number in the range from 3 to 2000, from 4 to 1000, also from 5 to 750, especially from 5 to 200, sometimes from 5 to 100. Z ¹ and Z ² are reactive functional groups, for example, independently of each other, hydroxy, carboxyl, aldehyde, amino or glycidyl groups, preferably hydroxy groups.

In the polymer described above, the functional group Z ¹ or Z ² present at one end reacts with the functional group present on the surface of the underlying layer or substrate and is fixed, and the other end forms the surface of the monomolecular layer. In some cases, repeated reaction between the other end of the fixed polymer and one end of another polymer extends the polymer chain having the polydimethylsiloxane structure. In this polymerization reaction, steric hindrance is so pronounced that cross-linking between polymer chains is virtually eliminated.

When the organic polymer is produced by polymerization of the monomers of formula (3), the organic polymer will contain bonds depending on the type of reactive functional group. For example, this bond becomes an ester bond when a carboxyl group and a hydroxy group react, and an amide bond when a carboxyl group and an amino group react. When dehydration condensation occurs between hydroxy groups, the resulting bond becomes a siloxane bond. In this case, a main chain containing only siloxane bonds as chemical bonds is produced. However, in any case, the main chain of the resulting organic polymer will contain a polydialkylsiloxane structure.

The thickness of the layer containing the organic polymer is preferably between 1 nm and 30 nm, more preferably between 1.5 nm and 20 nm, and optionally between 2 nm and 10 nm, and even between 2 nm and 8 nm.

The content of carbon atoms contained in the organic polymer per cm ² of membrane area is preferably 0.01 μg to 0.2 μg, particularly preferably 0.02 μg to 0.1 μg. The carbon atom content can be measured, for example, by thoroughly washing the surface and using an EPMA (electron probe microanalyzer).

(Contact angle and falling angle of film surface)
A layer containing an organic polymer exposed on the surface of the membrane increases the contact angle of water on this surface and reduces the sliding angle. A water contact angle of 90 degrees or more, further 95 degrees or more, particularly 100 degrees or more, and in some cases 110 degrees or more, is measured by dropping a water droplet having a mass of 4 mg on the surface of the film. However, the contact angle of water may be 140 degrees or less, further 130 degrees or less, particularly 120 degrees or less.

The falling angle of water measured by dropping a water droplet having a mass of 4 mg on the surface of the film can be reduced to 30 degrees or less, further to 25 degrees or less, particularly 20 degrees or less. However, the falling angle of water may be 3 degrees or more, further 5 degrees or more, particularly 8 degrees or more.

A layer containing an organic polymer exposed on the surface of the membrane reduces the contact angle of oleic acid on this surface. The contact angle of oleic acid measured by dropping an oil droplet of 4 mg mass of oleic acid on the surface of the film can be reduced to 50 degrees or less, even 45 degrees or less, especially less than 40 degrees. The contact angle of oleic acid may be 15 degrees or more, 20 degrees or more, or even 25 degrees or more. This degree of contact angle is slightly higher than the oleic acid contact angle (which is typically less than 10 degrees) that organic polymers containing perfluoroalkyl (alkylene) groups can exhibit.

(Cross section of one form)
FIG. 1 shows a cross-section of an example of an article according to the invention. The illustrated article 10 comprises a substrate 1 and a film 2 formed on its surface, the film 2 comprising an underlying layer 11 and a layer 12 formed on its surface. Layer 12 includes polymer brushes 20 of an organic polymer, with polymer brushes 20 exposed at surface 12s of layer 12 . The polymer brush 20 is composed of a chain polymer having one end fixed to the surface 11 s of the base layer 11 and the other end exposed to the surface 12 s of the layer 12 . Surface 12s is also the surface of membrane 2 . The surface 1s of the base material 1 is flat, but the surface 11s of the underlying layer 11 has a dome-shaped convex portion 11p and a flat portion 11f. The convex portion 11p is surrounded by the flat portion 11f. The protruding portion 11p is formed by protruding from the surface 11s of fine particles whose lower portion is embedded in the underlying layer 11 . A dome-shaped convex portion 12p derived from the convex portion 11p of the surface 11s is formed on the surface 12s, and the convex portion 12p is surrounded by a flat portion 12f. Ra of the surface 12s of the film 2 is in the range of 0.5 nm to 50 nm.

Polymer brush 20 preferably has a backbone comprising a polydialkylsiloxane structure and is flexible, unlike polymer brushes having perfluoroalkyl or perfluoroalkylene groups. Therefore, the polymer brush 20 is suitable for receiving oil droplets such as sebum while deforming as a whole, in other words, for absorbing the oil droplets. Further, when the organic polymer constituting the polymer brush 20 is formed from the polymer represented by the formula (3), the surface of the polymer brush 20 has functional groups (Z ¹ or Z ² ) will be exposed. For this reason, the surface of the polymer brush 20 does not have a higher affinity for oil droplets than the surface of the polymer brush on which the fluoroalkyl groups are exposed, and the contact angle of the oil droplets is slightly larger. On the other hand, the film is rich in hydrophobic alkyl groups (R ¹ and R ² ) and is highly lipophilic. Therefore, with such a polymer brush, droplets of oil such as sebum are likely to migrate from the surface of the film into the film and be absorbed.

The present invention will be described in more detail below with reference to examples. Film-coated glass plates were produced in the following examples and comparative examples. First, a method for evaluating the properties of the film-coated glass plate will be described.

(1) Characteristic evaluation by microscopic observation Observation of the surface of the film from obliquely above using a field emission scanning electron microscope (manufactured by Hitachi, Ltd., S-4500). and the height and thickness of the flat part of the film were measured. In addition, the surface of the film was observed using an atomic force microscope (manufactured by THERMOMICROSCOPE, scanning probe microscope), and the surface roughness Ra was calculated from an image of a 1 μm square visual field.

(2) Water contact angle and falling angle A 4 mg drop of water was dropped on the film surface of a film-coated glass plate placed so that the surface of the film was horizontal, and the contact angle of water was measured. In addition, the falling angle of a 4 mg water droplet dropped was also measured. Specifically, the angle formed by the surface of the film-coated glass plate and the horizontal plane was sufficiently slowly increased from 0 degrees, and the angle at which the water droplet started to move was taken as the falling angle of the water.

(3) Contact angle of oleic acid (contact angle of oil)
The oil contact angle was measured in the same manner as the water contact angle, except that 4 mg of oleic acid oil droplets were used instead of 4 mg of water droplets.

(4) Measurement of thickness of layer containing organic polymer (polymer thickness)
The reflectance was measured using an ellipsometer (VASE manufactured by JA Woollam), and the thickness of the molecular chain portion of the organic polymer was measured from the real part and the imaginary part of the reflectance.

(5) Fingerprint erasability (sebum erasability)
A 2 cm × 2 cm cotton cloth on which a 4 mg droplet of oleic acid was dropped was pressed against the film surface with a load of 300 g, and 10 seconds after removing the cotton cloth, the diffuse reflection color of the surface pressed with the cotton cloth was measured. The color difference ΔE ^* ab (SCE) in the L ^* a ^* b ^* color system of the two measured values was evaluated from the diffuse reflection color after pressing and the diffuse reflection color previously measured before pressing. The diffuse reflection color was measured using a spectrophotometer (CM-2500d, manufactured by Konica Minolta) with a circular visual field of 8 mm in diameter. In addition, 10 seconds after the removal of the cotton cloth, it was determined whether the portion to which the cotton cloth was pressed and the portion to which the cotton cloth was not pressed could be distinguished with the naked eye. The color difference ΔE ^* ab is calculated based on the following _{formula from two coordinates} (L1, a1, b1) and (L2, _a2 , _b2 ) of the L ^* _a ^* _b ^* color system. can do.
ΔE ^* ab=((L ₁ -L ₂ ) ² +(a ₁ -a ₂ ) ² +(b ₁ -b ₂ ) ² ) ^1/2

(6) Fingerprint removal property (sebum wiping property)
A cotton cloth of 2 cm×2 cm on which a droplet of 4 mg of oleic acid was dropped was pressed against the membrane surface with a load of 300 g, and then the cotton cloth was removed. A paper cloth (Kimwipe (registered trademark), manufactured by Nippon Paper Crecia Co., Ltd.) was applied with a load of 1 kg on the surface, and after reciprocating 10 times at a reciprocating speed of 1 second/reciprocating 10 cm, the diffuse reflection color of the surface was measured. . The color difference ΔE ^* ab (SCE) in the L ^* a ^* b ^* color system of the two measured values was evaluated from the diffuse reflection color after wiping and the diffuse reflection color previously measured before pressing with the cotton cloth. The diffuse reflection color was measured in the same manner as in (5). In addition, after wiping, it was determined whether or not it was possible to distinguish with the naked eye the portion wiped off with the paper cloth while the cotton cloth was pressed and the portion not pressed with the cotton cloth.

(7) Abrasion resistance Steel wool (#0000, oil-free) of 2 cm x 2 cm was pressed against the surface of the membrane with a load of 1 kg, and reciprocated 1000 times at an amplitude of 19 cm and a reciprocation frequency of 1 second/reciprocation. The water contact angle and fingerprint erasure and/or removability were then measured.

(Example 1)
A commercially available float glass plate with a thickness of 3 mm was cut into 10 cm squares, and the surface was thoroughly washed and dried. On the other hand, 7.05 parts by mass of tetraethoxysilane, 1.79 parts by mass of concentrated hydrochloric acid, 2.5 parts by mass of water, 19.7 parts by mass of ethanol, silica fine particle dispersion (manufactured by Fuso Chemical Industry, PL-7) 0.8 Parts by mass were mixed and stirred at 25° C. for 4 hours to obtain a stock solution. PL-7 contains substantially spherical solid silica fine particles with an average particle size of 100 nm at a solid content concentration of 23% by weight. Moreover, the solid content of the undiluted solution is 6% by mass. In the solid content, the ratio of the silicon oxide component contained in the fine particles and the silicon oxide component derived from tetraethoxysilane, which is the binder of the fine particles, was 8:92 on a mass basis in terms of SiO ₂ . 37 parts by mass of ethanol was added to the undiluted solution to obtain a base layer forming coating solution. PL-7 does not contain secondary particles.

This coating liquid is applied to the glass plate described above using a bar coater, and held in an electric furnace set at 100° C. for 2 hours to dry and solidify the coating liquid. A base layer having an uneven surface was formed on a glass plate.

A glass plate with an underlayer is placed in a flat container, and polydimethylsiloxane (Gelest Inc., DMS-12, average molecular weight 550) having one silanol group at each end is applied so as to cover the uneven surface of the underlayer. and was held in an electric furnace set at 120° C. for 24 hours. After that, the glass plate was washed with acetone, ethanol and water in that order, and the surface was wiped with the above paper cloth to remove polydimethylsiloxane remaining after the reaction, thereby obtaining a film-coated glass plate.

(Example 2)
The same glass plate as in Example 1 was similarly washed and dried. A methanol solution containing 0.5% by weight of poly (diallyl dimethyl ammonium chloride) (PDDA) was poured onto the glass plate and dried in a drier at 100° C. for 30 minutes. After that, a silica fine particle dispersion (IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd.) different from that in Example 1 was poured over the dried surface, and the excess liquid was allowed to flow down, followed by an electric furnace at 550 ° C. was held for 3 hours to bake, and then slowly cooled to room temperature over 8 hours. This silica fine particle dispersion liquid contains secondary particles with an average particle size of 40 nm, which are formed by associating solid silica fine particles with a primary particle size of 10 nm, at a solid content concentration of 25% by weight. The surface of the glass plate treated with PDDA is positively charged by PDDA, and the negatively charged silanol groups on the surface of the silica fine particles adsorb the silica fine particles to the glass surface. PDDA is burned off by the subsequent firing, and the silica fine particles are strongly bonded to the glass surface to form an underlying layer consisting of projections on the glass surface. Thereafter, this glass plate with the underlayer was treated in the same manner as in Example 1 to obtain a glass plate with a film.

(Example 3)
A glass plate with a film was prepared in the same manner as in Example 1 except that instead of the dimethyl silicone having an average molecular weight of 550, a dimethyl silicone having silanol groups at both ends and an average molecular weight of 26000 (manufactured by Gelest Inc., DMS-S45) was used. got

(Example 4)
A film-coated glass plate was obtained in the same manner as in Example 3, except that silica fine particle dispersion (IPA-ST-UP) was used instead of silica fine particle dispersion PL-7.

(Comparative example 1)
First, in the same manner as in Example 1, an underlayer having an uneven surface was formed on the surface of a glass plate. Next, a commercially available anti-fingerprint coating solution (Optool DSX, manufactured by Daikin Industries, Ltd.) obtained by diluting a fluorine-containing polymer to 20% by mass with perfluorohexane was further diluted with perfluorohexane to obtain a 0.1% by mass solution. was prepared. After 3 mL of this treatment liquid was applied to a cotton cloth and applied to the surface of the underlayer, excess adhesion of the treatment agent was wiped off with a new dry cotton cloth to obtain a film-coated glass plate. The fluorine-containing polymer contained in OPTOOL DSX is perfluoropolyether and contains many perfluoroalkylene groups.

(Comparative example 2)
A float glass plate was obtained by cutting, washing and drying in the same manner as in Example 1. This glass plate was evaluated as it was.

The evaluation results are summarized in Table 1. In each example, ΔE ^* ab(SCE) was 1.0 or less both before and after the durability test, and residual oleic acid could not be confirmed with the naked eye in the fingerprint erasability or removability test. On the other hand, the presence of oleic acid could be visually recognized in each comparative example. Further, in each example, the contact angle of water was maintained at 90 degrees or more even after the durability test.

The degree of polymerization n of the main chain constituting the organic polymer is 7 in Examples 1 and 2 and 350 in Examples 3 and 4 in terms of the layer thickness. The content of carbon atoms per 1 cm ² of film area is 0.04 μg in Examples 1 and 2, and 0.07 μg in Examples 3 and 4. This carbon atom comes from the side chain of the organic polymer. Further, the organic polymer used in each example had a Hansen total solubility parameter δtotal in the range of 10 to 20 MPa ^1/2 and a distance between coordinates to oleic acid in Hansen space of 8 MPa ^1/2 or less.

In addition, after holding the film-coated glass plate of each example in a freezer set at −15° C. for 3 hours, ice kept in the same freezer was brought into contact with the surface of the film-coated glass plate. It glides smoothly on the surface of the film and does not stick to it. The surface of each example has anti-icing properties. On the other hand, in each comparative example, ice adhered to the surface.

Claims (13)

comprising a substrate and a film formed on the substrate;
the membrane comprises a layer exposed on the surface of the membrane;
The surface roughness Ra of the surface is 0.5 nm to 50 nm,
An article, wherein said layer comprises a polymer brush of an organic polymer having a backbone comprising a polydialkylsiloxane structure.
However, one end of the organic polymer is fixed to the base layer or the base material included in the film separately from the layer, and the other end is exposed to the surface. 2. The article of claim 1, wherein the organic polymer does not contain perfluoroalkyl or perfluoroalkylene groups. 3. The article according to claim 1 or 2, wherein a contact angle measured by dropping a droplet of oleic acid having a mass of 4 mg on said surface is 15 degrees or more. 2. The article according to claim 1 , wherein the falling angle of water measured by dropping a water droplet having a mass of 4 mg on the surface is 30 degrees or less. The article according to any one of claims 1 to 4 , wherein a contact angle measured by dropping a droplet of oleic acid having a mass of 4 mg on the surface is less than 40 degrees. The article according to any one of claims 1 to 5 , wherein a water contact angle measured by dropping a water droplet having a mass of 4 mg on the surface is 90 degrees or more. The article according to any one of claims 1 to 6 , wherein the contact angle of water measured by dropping a water droplet having a mass of 4 mg on the surface is 140 degrees or less. Article according to any one of the preceding claims, wherein the organic polymer has a Hansen total solubility parameter δtotal in the range of 10-20 MPa ^1/2 . The article according to any one of claims 1 to 8 , wherein the organic polymer has a distance between coordinates of oleic acid in Hansen space of 8 MPa ^1/2 or less. The article according to any one of claims 1 to 9 , wherein the alkyl group contained in the polydialkylsiloxane structure has 1 to 6 carbon atoms. The article according to any one of claims 1 to 10 , wherein said surface has a dome-shaped convex portion and a flat portion. The article according to any one of the preceding claims, wherein said surface has protrusions and flats, said protrusions having a diameter of 10 nm to 200 nm and a height of 5 nm to 100 nm. 13. Any one of claims 1 to 12 , wherein the surface has convex portions and flat portions, and the ratio of the total area occupied by the convex portions to the area of the flat portions is in the range of 15:85 to 80:20. or the article according to item 1.

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