JP2000237678A - Hydrophilic coating film forming method, and hydrophilic coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method capable of realizing formation of a hydrophilic coating film high in hydrophilicity and to obtain such a coating film. SOLUTION: Titanium dioxide is vapor-deposited on the surface of a glass substrate 14 heated to 300 deg.C or higher to form a photocatalyst layer 18 whose titanium dioxide is converted to have an anatase type crystal structure. Subsequently, silicon dioxide is vapor-deposited on the photocatalyst layer 18 without introducing oxygen into the layer 18 to form a hydrophilic layer 20. Since the photocatalyst layer 18 becomes an uneven state by this method, the surface area of the photocatalyst layer 18 per a unit surface area of the glass substrate 14 becomes large. Further, by forming the hydrophilic layer 20 by the vapor deposition of silicon dioxide without introducing oxygen, the hydrophilic layer 20 becomes a state near to a bulk and has high density and does not become porous. Therefore, the oil component bonded on the hydrophilic layer 20 is easy to flow down and a residual oil component is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a hydrophilic film capable of securing hydrophilicity by decomposing oils and the like on a hydrophilic layer by a photocatalytic function. The present invention relates to a hydrophilic film forming method suitable for a hydrophilic film to be formed and a hydrophilic film.

[0002]

2. Description of the Related Art A vehicle is provided with a so-called side mirror (sometimes referred to as a door mirror or an outer view mirror) for confirming both left and right rear sides. As the reflecting mirror, a reflecting mirror in which a two-layer coating of a silicon dioxide layer and a titanium dioxide layer as described below is formed on a glass substrate is used.

[0003] That is, since this type of reflecting mirror is provided outside the vehicle, it is exposed to rain when it rains. At this time, if water droplets such as raindrops adhere to the surface of the reflecting mirror, the reflection image is distorted. Therefore, a hydrophilic film having a hydrophilic layer made of silicon dioxide (SiO ₂ ) is formed on the surface of the reflecting mirror. By improving the hydrophilicity of the surface and making the water attached to the surface thinner, distortion of the reflected image due to the attachment of water droplets is suppressed.

[0004] On the other hand, in this type of reflector, even during normal times, components of exhaust gas of other vehicles, oil (mainly organic substances) and the like may adhere to the surface of the reflector and become dirty. If the surface of the reflecting mirror is dirty, the hydrophilicity of the hydrophilic layer of the above-mentioned hydrophilic coating decreases. Therefore, the formed photocatalyst layer by the titanium dioxide (TiO ₂₎ or the like between the hydrophilic layer and the glass surface is provided, the hydrophilic coating of titanium dioxide in the vicinity of the surface of the organic substance adhering to the surface of the (hydrophilic layer) (TiO ₂ It has been considered that the hydrophilic layer is decomposed by a photocatalytic function such as (a) to recover and maintain the hydrophilicity of the hydrophilic layer.

[0005] The above-mentioned coating (layer) is first deposited,
A layer of titanium dioxide (photocatalyst) is applied to a glass substrate by a method such as ion plating or sputtering, or by applying a sol- or gel-like solution to the substrate, or by immersing the substrate in such a solution and then heating. Layer), followed by a porous silicon dioxide layer (hydrophilic layer).

[0006]

When a titanium dioxide layer (photocatalyst layer) has been formed on a glass substrate, the photocatalyst layer is first heated at a temperature of less than 300 degrees Celsius. After the film is formed, the glass substrate on which the titanium dioxide layer is formed is heated at 400 degrees Celsius by another heating device.
By heating at a temperature higher than or equal to the temperature, titanium dioxide constituting the photocatalytic layer was further made to have an anatase type crystal structure.

However, in the photocatalyst layer formed in this manner, there may be a part where the anatase type crystal structure is not formed, and the surface irregularities are small.
For this reason, satisfactory photocatalytic properties cannot be obtained, and there has been a long-felt need for a hydrophilic coating that can ensure high hydrophilicity due to a photocatalytic layer having higher photocatalytic properties.

On the other hand, the hydrophilic layer of the conventional hydrophilic coating is porous having a large number of through holes penetrating the surface side and the photocatalyst layer side, and the photocatalyst layer is formed through the formed holes. The photocatalytic function on the surface of the hydrophilic layer was exhibited by exposing it to the surface side of the hydrophilic layer.

However, if the hydrophilic layer is made porous,
Impurities such as oil that impairs hydrophilicity are less likely to flow off the hydrophilic layer. Therefore, the amount of decomposition of impurities due to the photocatalytic function increases, and as a result, recovery of hydrophilicity in the hydrophilic layer is delayed. The fact that the recovery is slow means that at least the hydrophilicity at that time is low.Therefore, in this sense, the hydrophilicity of the conventional hydrophilic coating cannot be said to be high. Longed for.

In view of the above, an object of the present invention is to provide a method for forming a hydrophilic film and a method for forming a hydrophilic film having high hydrophilicity.

[0011]

According to a first aspect of the present invention, there is provided a photocatalytic layer having a photocatalytic property formed on a substrate with titanium dioxide as a main component, and the photocatalytic layer with a silicon oxide as a main component. And a hydrophilic layer having hydrophilicity formed on the side opposite to the above, and a hydrophilic film forming method for forming a hydrophilic film including the hydrophilic layer, wherein the substrate is heated to 300 ° C. or more. And the photocatalyst layer is formed on the substrate in the heated state.

In the method of forming a hydrophilic film having the above structure, first, the substrate is heated to 300 ° C. or more, and a photocatalytic film containing titanium dioxide as a main component is deposited, ion-plated, or The film is formed by a method such as sputtering. In the present forming method, by heating the substrate to 300 ° C. or more, the crystal structure of titanium dioxide becomes anatase in the film forming process, and the crystallinity of anatase increases, and the surface of the photocatalytic film becomes uneven. Thereby, the surface area of the photocatalytic film increases, and the photocatalytic function improves.

[0013] In addition, since the titanium dioxide film is formed on the substrate and then reheated to make the crystal structure of titanium dioxide anatase, the number of steps is reduced by one step, so that productivity is reduced. improves.

According to a second aspect of the present invention, there is provided a photocatalytic layer having titanium oxide as a main component and having a photocatalytic property formed on a substrate, and a photocatalytic layer formed mainly of silicon oxide on a side opposite to the substrate of the photocatalytic layer. A hydrophilic layer having a hydrophilic property, and a hydrophilic film forming method for forming a hydrophilic film comprising the above, comprising: evaporating silicon oxide on the photocatalytic layer in an oxygen-free state; Forming a hydrophilic layer.

In the method of forming a hydrophilic film having the above-mentioned structure, when the hydrophilic layer is deposited on the photocatalyst layer without introducing oxygen, the hydrophilic layer is in a state close to a bulk, and has a high density and high porosity. It is not quality. This makes it easier for oil or the like adhering to the hydrophilic layer to flow down. For this reason, in the hydrophilic film formed in this manner, even if oil adheres, the oil flows down and the residual oil on the film (on the hydrophilic layer) is reduced, so that it must be decomposed by the photocatalytic function of the photocatalytic layer. Low oil content. As a result, the recovery of hydrophilicity is accelerated.

According to a third aspect of the present invention, there is provided a photocatalytic layer having a photocatalytic property formed on a substrate with titanium dioxide as a main component, and a photocatalytic layer formed on a side opposite to the substrate with the silicon oxide as a main component. And a hydrophilic layer having a hydrophilic property, wherein the substrate is heated to 300 degrees Celsius or more while the substrate is heated. The photocatalyst layer is formed on the photocatalyst layer, and after the photocatalyst layer is formed, silicon oxide is deposited on the photocatalyst layer in an oxygen-free state to form the hydrophilic layer.

In the method for forming a hydrophilic film having the above structure, first, the substrate is heated to 300 ° C. or higher, and a photocatalytic film containing titanium dioxide as a main component is deposited, ion-plated, or The film is formed by a method such as sputtering. In this formation method, the crystal structure of titanium dioxide is converted to anatase in the film formation process by heating the substrate to 300 ° C. or higher. Therefore, the number of steps is reduced by one in comparison with the conventional formation method in which the crystal structure of titanium dioxide is changed to anatase by reheating after film formation, thereby improving the productivity.

When the substrate is heated to 300 ° C. or more to form a film, irregularities are formed on the surface of the photocatalytic film.
Thereby, the surface area of the photocatalytic film increases, and the photocatalytic function improves.

Furthermore, in the present forming method, when the hydrophilic layer is deposited on the photocatalyst layer without introducing oxygen, the hydrophilic layer is in a state close to a bulk, and has a high density and is porous. No. This makes it easier for oil or the like adhering to the hydrophilic layer to flow down. For this reason, in the hydrophilic film formed in this manner, even if oil adheres, the oil flows down and the residual oil on the film (on the hydrophilic layer) decreases, so that it must be decomposed by the photocatalytic function of the photocatalytic layer. Low oil content. As a result, the recovery of hydrophilicity is accelerated.

When a hydrophilic layer is formed by depositing silicon oxide on the surface of the photocatalyst layer having an uneven surface under the above conditions, the hydrophilic layer is formed mainly on the projections of the photocatalyst layer.
For this reason, the photocatalytic layer is exposed to the outside more, the photocatalytic function can be maintained, and the amount of decomposition of the photocatalytic layer by the photocatalytic function increases.

[0021] The hydrophilic film according to claim 4 is formed on a substrate with titanium dioxide having an anatase crystal structure as a main component, and has a concavo-convex shape having a height difference of 20 nm or more along a substantially surface direction of the substrate. A photocatalytic layer having photocatalytic properties, and a hydrophilic layer having silicon oxide as a main component and having hydrophilicity formed on the side opposite to the substrate via the photocatalytic layer.

In the hydrophilic coating having the above structure, water droplets attached to the surface due to the hydrophilic property of the hydrophilic layer have a small contact angle and spread substantially in a film shape. Further, when oil adheres to the hydrophilic layer, the hydrophilicity of the hydrophilic layer is reduced. However, the oil is decomposed by the photocatalytic function of the photocatalytic layer provided between the hydrophilic layer and the substrate, so that the hydrophilic layer is decomposed. Is restored.

Here, in the present hydrophilic film, a photocatalyst layer is formed mainly of titanium dioxide having an anatase type crystal structure. In addition, this photocatalyst layer has an uneven surface having a height difference of 20 nm or more (that is, a difference from the lowest position to the highest position) along the substantially surface direction of the substrate. Alternatively, it is different from the photocatalyst layer on the surface having relatively small irregularities. With such an uneven shape, the surface area of the photocatalyst layer is larger than that of the conventional photocatalytic layer having a hydrophilic coating, and the photocatalytic function is improved.

In the above-described production method according to the first to third aspects and the hydrophilic film according to the fourth aspect, the silicon oxide constituting the hydrophilic layer is silicon dioxide (Si).
O ₂ ) or silicon monoxide (SiO).

[0025]

FIG. 1 shows the structure of a reflecting mirror 12 having a hydrophilic coating 10 (that is, a hydrophilic coating 10 formed by the manufacturing method of the present invention) according to an embodiment of the present invention. The outline is shown by a schematic sectional view.

As shown in this figure, the reflecting mirror 12 has a glass substrate 14 as a substrate. Although the glass substrate 14 is entirely colorless and transparent or transparent, it is entirely colored blue or greenish so that all light or light in a predetermined wavelength range can be transmitted.

One side in the thickness direction of the glass substrate 14 (FIG. 1)
A reflection film 16 is formed on a surface on the side opposite to the arrow RE). The reflection film 16 is formed of, for example, chromium or an alloy containing chromium as a main component, and has a thickness of about 35 nm or more. At least the surface of the reflection film 16 formed on the glass substrate 14 on the glass substrate 14 side has a sufficient gloss and a high light reflectance. Therefore, light incident on the glass substrate 14 from the side of the glass substrate 14 where the reflective film 16 is formed is reflected by the reflective film 16.

In the present embodiment, the reflection film 16 is formed of chromium or a metal containing chromium as a main component. However, the configuration of the reflection film 16 is not limited to this, and other metals, for example, Aluminum, silver, or an alloy mainly containing these metals may be used.

On the opposite side of the glass substrate 14 from the reflection film 16, a hydrophilic coating 10 composed of a photocatalyst layer 18 and a hydrophilic layer 20 is formed. The photocatalyst layer 18 of the hydrophilic film 10 is mainly composed of titanium dioxide (TiO ₂ ) and has an average thickness of 50 nm or more. Directly formed. Further, among the three titanium dioxide transformation modes of rutile type, brookite type and anatase (anatase) type, the photocatalyst layer 18 is formed so as to be a tetragonal anatase type (so-called “anatase type titanium oxide”).
Is). Furthermore, the photocatalyst layer 18 has a large unevenness (columnar shape) with a large difference in height as compared with the surface of the conventional hydrophilic coating photocatalyst layer, and the height difference (the photocatalyst layer 18 along the surface direction of the glass substrate 14). (The height from the top of the convex to the bottom of the concave) is 20 nm or more. Therefore, the photocatalyst layer 18 per unit surface area of the glass substrate 14
Is larger than the surface area of the photocatalytic layer of the conventional hydrophilic coating.

Further, the glass substrate 1 of the photocatalyst layer 18
A hydrophilic layer 20 is formed on the surface opposite to the surface 4. The main component of the hydrophilic layer 20 is silicon dioxide, and its average thickness is 30 nm or less. As shown in FIG. 1, among the irregularities on the surface of the photocatalyst layer 18, the hydrophilic layer 20 is mainly formed on the projection of the photocatalyst layer 18, and the hydrophilic layer 20 is formed on the projection of the photocatalyst layer 18. The thickness is large, and the hydrophilic layer 20 is not formed in the concave portion of the photocatalyst layer 18, or even if formed, it is extremely thin compared to the average thickness. That is, the hydrophilic layer in the conventional hydrophilic film is basically formed uniformly on the photocatalytic layer,
Since the hydrophilic layer was porous, a part of the photocatalyst layer was exposed to the outside. In contrast, the present hydrophilic coating 1
In the case of 0, the surface of the photocatalyst layer 18 is made uneven, and the hydrophilic layer 20 is formed intermittently on the photocatalyst layer 18 by forming the hydrophilic layer 20 on the photocatalyst layer 18 by a method described later. That is, the photocatalyst layer 18 is exposed from the gaps between the respective portions of the hydrophilic layer 20.

Next, a method for forming the present hydrophilic film 10 (manufacturing method) will be described.

In the method of forming the hydrophilic coating 10, first,
The glass substrate 14 is set in a vapor deposition apparatus, and the glass substrate 1
4 Heat the whole to 300 degrees Celsius or more. Next, in this state, titanium dioxide (Ti
O ₂ ) is deposited to form the photocatalyst layer 18. Here, as described above, when the titanium dioxide is deposited, the glass substrate 14 has already been heated to 300 ° C. or more, and therefore, when the titanium dioxide is deposited,
When the photocatalyst layer 18 is formed thereon, the titanium dioxide has an anatase-type crystal structure. Moreover, the glass substrate 14
Is heated to 300 ° C. or more, the titanium dioxide is not deposited on the glass substrate 14 on average, and the surface thereof has unevenness with a height difference of 20 nm or more (especially, relatively Column with a high convex portion).

Next, the glass substrate 1 on which titanium dioxide is deposited and the photocatalyst layer 18 is formed on the surface in this manner.
4, a hydrophilic layer 20 is further formed. The hydrophilic layer 20 is also formed by depositing silicon dioxide on the surface of the photocatalyst layer 18 similarly to the photocatalyst layer 18. However, when forming a hydrophilic layer of a hydrophilic coating so far, silicon dioxide was vapor-deposited while introducing oxygen into the vapor deposition apparatus. However, in the present forming method, oxygen was not introduced into the vapor deposition apparatus. The silicon dioxide is deposited (ie, essentially free of oxygen). Thereby, the hydrophilic layer 20 is in a state close to a so-called bulk state with respect to the interface with the photocatalyst layer 18. Moreover, as described above, the surface of the photocatalyst layer 18 has an uneven shape with a height difference of 20 nm or more. By depositing silicon dioxide on the surface of the photocatalyst layer 18 under such conditions, the photocatalyst layer is mainly formed. Silicon dioxide is deposited on the projections 18. Thereby, the hydrophilic layer 20
Does not become as porous as the hydrophilic layer of a conventional hydrophilic coating, but rather a large number of
Will be formed on the surface.

Here, FIG. 2 shows a traced observation result obtained by observing the surface of the hydrophilic coating 10 formed by the above-described manufacturing method using an atomic force microscope.
FIG. 3 is a diagram tracing observation results obtained by observing the surface of a hydrophilic film formed by a conventional manufacturing method using an atomic force microscope. As can be seen by comparing these figures, the hydrophilic film 10 formed by the present manufacturing method can be used.
It can be seen that the surface roughness is larger than that of the hydrophilic film formed by the conventional method.

FIG. 4 is a table showing the results of observing the surface and crystal structure of the hydrophilic film 10 and the hydrophilic film formed by the conventional manufacturing method using an atomic force microscope and X-ray diffraction. Are indicated by. The observation conditions in this table (FIG. 4) will be briefly described. The upper middle part of the table shows the actual measurement range (effective heating temperature) of the temperature of the glass substrate 14.
Since the measurement is performed by visually checking the scale of the meter of the measuring device, the measured value has a certain range. Further, as shown in the top row of the table, the measurement range where the measured temperature range is less than 300 degrees Celsius (that is, the range of 225 degrees Celsius to 240 degrees Celsius and the range of 280 degrees Celsius to 295 degrees Celsius) is the conventional range. In the photocatalyst layer formed by the manufacturing method, the actual measurement range of the temperature is 300 degrees Celsius or more (that is, the range of 300 degrees Celsius to 315 degrees Celsius and the range of 320 degrees Celsius to 340 degrees Celsius). Is the photocatalyst layer 18 formed by On the other hand, the middle and lower parts of the table show values indicating the height difference of the surface of the conventional photocatalyst layer and the height difference of the photocatalyst layer 18 formed by the forming method of the present invention, and are results of observation by an atomic force microscope. The bottom row of the table shows the state of each crystal structure as a result of analyzing a sample in each measurement range by X-ray diffraction.

As can be seen from this table (FIG. 4), the height difference of the photocatalyst layer formed by the conventional manufacturing method is 5 to 1%.
It is as small as 0 nm. On the other hand, in the photocatalyst layer 18 formed by the formation method of the present invention, the height difference of the surface (that is, the height from the top of the projection to the bottom of the recess) of the photocatalyst layer 18 is 2.
5 nm.

Further, the crystal structure shows an amorphous state instead of an anatase type at a relatively low temperature of 225 ° C. to 240 ° C. in the conventional manufacturing method, and a temperature of 280 ° C. to 295 ° C. higher than this. In the range of degrees, it becomes weak anatase type. In contrast, the present hydrophilic film 10
The photocatalyst layer 18 has an anatase-type crystal structure at any temperature range from 300 degrees Celsius to 315 degrees Celsius and from 320 degrees Celsius to 340 degrees Celsius.

Next, the present hydrophilic film 10 having both the hydrophilic layer 20 and the photocatalyst layer 18 and the hydrophilic film having one of the hydrophilic layer 20 and the photocatalyst layer 18 and forming the other by a conventional manufacturing method are described. 3 shows the results of comparing. The evaluation method in comparison is as follows.

First, an oil 22 is dropped onto each surface of the hydrophilic film 10 and the other hydrophilic film formed by a conventional method (see FIG. 5). Next, the present hydrophilic coating 10 and either of them are held such that each surface direction of the hydrophilic coating formed by the conventional manufacturing method is substantially orthogonal to the vertical direction, and in this state, the present hydrophilic coating 10 and either On the other side, a predetermined amount of running water 24 is applied from above to each surface of the hydrophilic film formed by a conventional manufacturing method for a predetermined time (see FIG. 6). A certain amount of the oil 22 flows down together with the running water 24, and the remaining oil spreads as an oil film 26 on the surface of the hydrophilic coating 10 or one of the hydrophilic coatings formed by a conventional manufacturing method. The water droplet 2 is formed on the oil film 26 thus formed.
8, the contact angle of the water droplet 28 is first measured (see FIG. 7), and then the light intensity is applied to each surface of the hydrophilic film 10 and the other surface of the hydrophilic film formed by a conventional method. Irradiates ultraviolet rays of 1 mW / cm ² at a wavelength of 365 nm (see FIG. 8). Hydrophilic coating 1 by irradiated ultraviolet light
The zero photocatalyst layer 18 and the photocatalyst layer of a hydrophilic film formed on either side by a conventional manufacturing method have a photocatalytic action and decompose the oil film 26. After irradiating ultraviolet rays for a predetermined time, a water droplet 28 is dropped on each surface of the hydrophilic film 10 and the other hydrophilic film formed by the conventional method again, and the contact angle of the water droplet 28 at this time is measured (FIG. 9).

As a result of performing the above operations, the relationship between the ultraviolet irradiation time and the contact angle of the water droplet 28 is shown in the graph of FIG.

In this graph, a curve indicated by an arrow A represents a hydrophilic layer equivalent to the hydrophilic layer 20 of the present hydrophilic film 10 (that is, a non-porous hydrophilic layer) and a photocatalytic layer formed by a conventional manufacturing method. In the data of a hydrophilic film (hereinafter, for convenience, this hydrophilic film is referred to as “hydrophilic film A”), a curve indicated by an arrow B indicates a hydrophilic layer formed by a conventional manufacturing method and a hydrophilic layer formed by a conventional manufacturing method. Data of a hydrophilic coating (hereinafter, for convenience, this hydrophilic coating is referred to as “hydrophilic coating B”) in which a photocatalytic layer equivalent to the photocatalytic layer 18 of the coating 10 (that is, a photocatalytic layer having irregularities) is combined,
The curve indicated by arrow C indicates the hydrophilic layer 20 and the photocatalyst layer 18.
3 is data of the present hydrophilic coating 10 having both of the above.

First, the hydrophilic film A and the hydrophilic film A having a difference in the structure of the photocatalytic layer are compared. As described above, the surface area of the photocatalyst layer 18 of the hydrophilic film 10 is made uneven, so that the surface area of the photocatalyst layer 18 is larger than that of the photocatalyst layer of the hydrophilic film A, and the substantial photocatalytic function is improved. As a result, the amount of oil decomposed per unit time increases. For this reason, as shown in FIG. 10, the contact angle of the water droplet 28 between the hydrophilic film 10 and the hydrophilic film A before the UV irradiation is almost the same as about 50 degrees, but the UV light irradiation for about 3 hours is performed. Thus, the hydrophilic film 10 can make the contact angle of the water droplet 28 less than about 10 degrees, and can improve the wettability in a short time. On the other hand, even if the hydrophilic film A is irradiated with ultraviolet rays for about 3 hours, the contact angle of the water droplet 28 is only about 40 degrees, and the ultraviolet rays for about 21 hours (that is, about 24 hours in total) Even if the irradiation is performed, the contact angle of the water droplet 28 does not fall below about 20 degrees.

Next, the hydrophilic film 10 and the hydrophilic film B having a difference in the structure of the hydrophilic layer will be compared. As mentioned above,
Since the hydrophilic layer 20 of the hydrophilic coating 10 is not as porous as the hydrophilic layer of the hydrophilic coating B, the attached oil tends to flow down, and the residual oil after running water 24 is more hydrophilic than the hydrophilic coating B. The coating 10 is less. Hydrophilic coating 10
Photocatalytic layer (or photocatalytic layer 18)
If the amount of decomposition of the oil component per unit time is the same, the time required for the hydrophilic layer 20 of the hydrophilic coating 10 having less residual oil component to restore the hydrophilicity is shorter. Therefore, FIG.
As shown in FIG. 0, the contact angle of the water droplet 28 before the ultraviolet irradiation is about 80 degrees in the hydrophilic film B, whereas the contact angle of the hydrophilic film 10 is as small as about 50 degrees, and the wettability is good.

When the above results are applied to a case where the present invention is actually applied to a door mirror for a vehicle, in a door mirror to which the present hydrophilic coating 10 is applied, the oil content of the hydrophilic coating 10 during rainfall is reduced.
Even if it adheres to the surface of the surface, the oil will easily flow down by being exposed to rain, so that the oil remaining on the surface of the hydrophilic coating 10 can be reduced. Moreover, as described above, the surface of the photocatalyst layer 18 is made uneven so as to substantially improve the photocatalytic action, whereby the amount of oil decomposed per unit time can be improved. Therefore, when the present hydrophilic film 10 is applied to a door mirror, the hydrophilicity of the photocatalytic layer 18 (that is, wettability on the surface of the hydrophilic film 10) can be sufficiently ensured as compared with the case where a conventional reflecting mirror is used.

Further, as an advantage from the viewpoint of the manufacturing process, as described above, the hydrophilic coating 10 has a glass substrate 1
4 is heated to 300 degrees Celsius or more, and then titanium dioxide is deposited on the glass substrate 14 to form the photocatalyst layer 18. After the deposition, the titanium dioxide of the photocatalyst layer 18 has an anatase type crystal structure. I have. On the other hand, conventionally, titanium dioxide is deposited in a state where the glass substrate is heated at a temperature of less than 300 degrees Celsius, and then reheated at a temperature of 400 degrees Celsius or more to form the titanium dioxide into an anatase-type crystal structure.
That is, while the heating step was conventionally two steps,
In the present hydrophilic film 10, only one heating step is required. Therefore, the number of manufacturing steps can be reduced, which contributes to cost reduction.

In the present embodiment, the hydrophilic film 10 is formed directly on the glass substrate 14. However, for example, as shown in FIG. In between, a sodium diffusion limiting coating 30 for preventing diffusion of sodium ions in the glass substrate 14 into the hydrophilic coating 10 may be formed. The sodium diffusion limiting film 30 at this time is mainly formed of, for example, silicon dioxide (SiO ₂ ) and has a thickness of 30 n.
m or more silicon dioxide layers.

In the present embodiment, silicon dioxide (S
Although the layer formed by iO ₂ ) was the hydrophilic layer 20,
The main component of the hydrophilic layer 20 may be silicon oxide. Therefore, a layer containing silicon monoxide (SiO) as a main component instead of silicon dioxide may be used as the hydrophilic layer.

[0048]

As described above, the hydrophilic film formed by the method of the present invention and the hydrophilic film of the present invention can ensure high hydrophilicity.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a reflector having a hydrophilic film according to one embodiment of the present invention.

FIG. 2 is a trace diagram of an observation result obtained by observing a surface of a photocatalytic layer of a hydrophilic film formed by a forming method of the present invention with an atomic force microscope.

FIG. 3 is a trace diagram of an observation result obtained by observing the surface of a photocatalytic layer of a hydrophilic film formed by a conventional forming method using an atomic force microscope.

FIG. 4 is a table showing the measurement results obtained by measuring the difference in height and crystal structure between a photocatalyst layer formed by the formation method of the present invention and a photocatalyst layer formed by a conventional formation method.

FIG. 5 is a diagram showing a state in which oil is dropped on the surface of the reflecting mirror.

FIG. 6 is a diagram showing a state in which running water is flowing on the surface of the reflecting mirror and oil on the surface is flowing.

FIG. 7 is a diagram showing a state in which water droplets are dropped on an oil film on the surface of a reflecting mirror.

FIG. 8 is a diagram showing a state in which ultraviolet light is irradiated on the surface of the reflecting mirror.

FIG. 9 is a diagram showing a state in which a water droplet is dropped on the surface of the reflecting mirror after irradiation with ultraviolet rays.

FIG. 10 is a graph comparing the characteristics of a hydrophilic film formed by a conventional method and a hydrophilic film formed by the method of the present invention, showing the relationship between the time of ultraviolet irradiation and the contact angle of a water droplet dropped on the surface. FIG.

FIG. 11 is a schematic sectional view of another embodiment of a reflecting mirror having a hydrophilic film formed by the forming method of the present invention.

[Explanation of symbols]

 Reference Signs List 10 hydrophilic film 14 glass substrate (substrate) 18 photocatalyst layer 20 hydrophilic layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 5/00 C09D 5/00 L 4J038 Z 4K029 C23C 14/10 C23C 14/10 G02B 1/10 G02B 1 / 10Z (72) Inventor Kie Fukui 3-260 Toyota, Oguchi-cho, Niwa-gun, Aichi Prefecture Inside Tokai Rika Electric Works, Ltd. F-term (reference) in Electric Works 2K009 BB02 CC03 DD03 EE05 3D025 AA04 AC20 AD01 AD13 4D075 BB23Y BB85Y CA34 CA37 DA06 DB13 DC13 EC02 EC10 4G059 AA01 AA11 AB11 AC21 EA04 EA05 EB03 GA01 BA04 BA03 BA04 DA05 FB02 4J038 AA011 HA216 HA441 KA04 NA06 PA07 PA19 PB07 4K029 AA09 AA24 BA17 BA35 BA46 BA48 BB02 CA01

Claims (4)

[Claims] 1. A photocatalytic layer having a photocatalytic property formed on a substrate with titanium dioxide as a main component, and a hydrophilic film formed on the opposite side of the photocatalytic layer from the photocatalytic layer with silicon oxide as a main component. A method for forming a hydrophilic film, comprising: forming a hydrophilic film, comprising: heating the substrate to 300 ° C. or higher and forming the photocatalytic layer on the heated substrate. A method for forming a hydrophilic film, comprising: 2. A photocatalytic layer having titanium oxide as a main component and formed on a substrate and having photocatalytic properties, and a hydrophilic layer having silicon oxide as a main component and being formed on the opposite side of the photocatalytic layer from the substrate. A hydrophilic film forming method for forming a hydrophilic film, comprising: forming a hydrophilic film by depositing silicon oxide on the photocatalytic layer in an oxygen-free state. A method for forming a hydrophilic film, characterized in that: 3. A photocatalytic layer having a photocatalytic property formed on a substrate with titanium dioxide as a main component, and hydrophilic having a hydrophilic property formed on a side opposite to the substrate with the photocatalytic layer containing silicon oxide as a main component. A method for forming a hydrophilic film, comprising: forming a hydrophilic film, comprising: heating the substrate to 300 ° C. or higher and forming the photocatalytic layer on the substrate in the heated state. Forming a hydrophilic layer by depositing silicon oxide on the photocatalyst layer in an oxygen-free state after forming the photocatalyst layer. 4. A photocatalytic layer formed on a substrate with titanium dioxide having an anatase crystal structure as a main component, and having a photocatalytic property in which a height difference along a substantially surface direction of the substrate is 20 nm or more. And a hydrophilic layer having silicon oxide as a main component and having hydrophilicity formed on the opposite side to the substrate via the photocatalyst layer.