Patent Description:
For example, for driving support of the vehicle, it is performed to mount the vehicle-mounted camera to the vehicle. More specifically, a camera for imaging the rear or side of the vehicle is mounted on the vehicle body of the vehicle, to reduce the blind spot by displaying the image captured by the camera in a position visible to the driver, thereby contributing to safe driving. Incidentally, the vehicle-mounted camera is often attached to the outside of the vehicle, and water droplets are often attached by rain on the lens. Depending on the degree of water droplets adhering to the lens, distortion occurs in the image captured by the camera, there is a fear that visibility is deteriorated.

Conventionally, as a technique for transporting a minute amount of droplets, a technique for transporting a droplet to a weaker hydrophobic surface and a larger area by arranging regions having different hydrophobic surfaces in a wedge shape has been disclosed (for example, see Patent Document <NUM>). However, when trying to apply the technique to the lens of the imaging system, since the boundary is present in regions with different contact angles, the optical characteristics are rapidly changed, and there is a problem that the image is disturbed. In addition, a semiconductor process is required to cope with micro water droplets below the dimensions of the pattern, and the productivity is significantly reduced, consequently, it is difficult to transport such micro water droplets.

Further, a technique is disclosed in which a hydrophilic coating and a water-repellent coating are applied to a surface of a lens, regions having different contact angles are provided on the same surface, and water droplets are concentrated and guided to one point in a guide at a boundary portion of the region (for example, see Patent Document <NUM>). However, the removal of water droplets is left to its own weight, and there is no force for moving water droplets to the lens surface itself, and the hydrophilic coating and the water-repellent coating are only a guide role for controlling the direction of movement when water droplets naturally fall.

Patent Document <NUM> describes a fluid guiding surface comprising a first elongate directional band A on a substrate, wherein a surface energy of a surface of the first elongate directional band A exhibits a first water contact angle at <NUM>° C; and a second elongate directional band B proximate the first elongate directional band A on the substrate, wherein a surface energy of a surface of the second elongate directional band B exhibits a second water contact angle at <NUM>° C, wherein the difference between the first water contact angle on the surface of directional band A and the second water contact angle on the surface of directional band B is between <NUM>°-<NUM>°.

Patent Document <NUM> describes a method of modifying the wetting properties of the surface of a substrate, the method comprising the steps of: (A) applying a first mold having an imprint forming surface to said substrate to form a first imprint thereon, said imprint forming surface being chosen to modify the wetting properties of the substrate surface; (B) applying a second mold having an imprint forming surface to said first imprint to form a second imprint on said first imprint; and (C) orienting, during said applying step (B), said second mold relative to said first imprint, wherein said orienting and said first and second imprint dimensions are selected to modify the wetting properties of the substrate surface.

Patent Document <NUM> describes a method for detecting an alcohol concentration with a gradient wetted surface. The method utilizes the property that alcohol with different concentrations has different flow lengths on a gradient wetted surface to establish a standard library with alcohol concentration and its flow length on the gradient wetted surface in one-to-one correspondence. For detecting the alcohol concentration, a dropper is employed to suck an alcohol solution so as to measure the flow length of the solution on the gradient wetted surface, and the length is compared with the flow length-alcohol concentration standard library so as to obtain the concentration of the alcohol to be detected.

Patent Document <NUM> describes a microfluid controlling structure wherein a conductive substrate of the structure is provided with a medium layer. The medium layer is provided with a thinning liquid layer; and both sides of the thinning liquid layer are provided with two side barrier walls. The two side barrier walls are provided with top end barrier walls. A flowing cavity is formed by a space among the thinning liquid layer, the two side barrier walls and the top end barrier walls. A microfluid is positioned in the flowing cavity; and the thickness of the medium layer is gradually reduced along the flowing direction of the microfluid so as to realize that the microfluid flows to one end with stronger wettability.

The present invention has been made in view of the above-mentioned problems and situation, and an object of the present invention is to provide a transparent member and a method of manufacturing a transparent member which can remove water droplets on a surface by a simple method and can clearly maintain a photographed image when used in a lens.

In order to solve the above-mentioned problems, the present inventor has found that, in the process of examining the problem of the above-mentioned problems, by forming a surface portion in which the contact angle with respect to water changes continuously, it is possible to easily remove water droplets adhering to the surface, and to provide a transparent member capable of clearly maintaining a photographed image. In other words, the above problem according to the present invention is solved by the transparent member, use and manufacturing method as defined in the appended claims.

According to the above-mentioned means of the present invention, it is possible to provide a transparent member and a method of manufacturing the transparent member which can remove water droplets on the surface by a simple method and can clearly maintain a photographed image when used in a lens. The expression mechanism or action mechanism of the effect of the present invention is not clarified, but is inferred as follows. Since the surface portion has a continuously changing contact angle with respect to water, a force (driving force) for moving the water droplet is applied to the surface portion regardless of the amount of change in the contact angle. Therefore, when a water droplet adheres to the surface portion, the water droplet naturally slides down in the direction of decreasing the contact angle, and the water droplet is removed from the surface portion. Therefore, when such a transparent member is used for a lens used outdoors, such as a vehicle-mounted camera or a surveillance camera, the photographed image is not distorted and the visibility is improved. In addition, water droplets are difficult to adhere to the lens, and good visibility may be maintained even in bad weather conditions.

The transparent member of the present invention is a transparent member comprising a base material provided with a water-repellent layer on the base material, wherein the transparent member has a surface portion in which a contact angle to water changes continuously, wherein the water-repellent layer includes said surface portion, and wherein the thickness of the water-repellent layer changes continuously, and the flow direction of water adhering to the surface portion is controlled. These features are technical features common to or corresponding to each of the following embodiments.

In the present invention, the surface portion is contained in the water-repellent layer in view of excellent water droplet removal. In addition, the thickness of the water repellent-layer changes continuously in terms of more conveniently removing water droplets. It is preferable that the water-repellent layer contains a fluoride in view of easy adjustment of the contact angle with respect to water and large contact angle. It is preferable to have an antireflection layer on the rear surface of the water-repellent layer from the viewpoint of excellent optical performance. It is preferable that the surface roughness of the surface portion changes continuously in terms of controlling the flow direction of water by changing the surface energy. It is preferable to be used for an optical component for vehicle use or outdoor use in terms of preventing water droplets from adhering due to rain and obtaining good visibility. In particular, it is preferable that the optical component is an optical lens.

The method of manufacturing a transparent member of the present invention includes a step of forming a water-repellent layer by forming a film of a water-repellent material, and in the above-mentioned step, the thickness of the water-repellent layer changes continuously. In the above step, it is preferable to use either the vapor deposition method or the coating method because water droplets may be more easily removed.

Hereinafter, the present invention and the constitution elements thereof, as well as configurations and embodiments to carry out the present invention, will be detailed in the following. In the present description, when two figures are used to indicate a range of value before and after "to", these figures are included in the range as a lowest limit value and an upper limit value.

The transparent member of the present invention is a transparent member comprising a base material provided with a water-repellent layer on the base material, wherein the transparent member has a surface portion in which a contact angle to water changes continuously, wherein the water-repellent layer includes said surface portion, and wherein the thickness of the water-repellent layer changes continuously.

In the present invention, "changes continuously" means that the difference between the maximum value and the minimum value of the contact angle in a specific region is preferably <NUM>° or more, and when the difference is <NUM>° or more, a force (driving force) for sufficiently moving the water droplet acts. In particular, when the transparent member of the present invention is used for a lens for a vehicle-mounted camera, it is preferable to set the contact angle to <NUM>° or more. In addition, the larger the amount of change in the contact angle, the greater the force for moving the water droplet, and the smaller the amount of change, the smaller the force for moving the water droplet, but in the region where the contact angle continuously changes, the force for moving the water droplet acts regardless of the amount of change. When the transparent member of the present invention is used in a circular lens, for example, it is preferable to set the amount of change from the center of the lens to the outside in the radial direction to be as large as possible. The maximum contact angle itself does not necessarily have to be large (i.e., it does not have to be a water-repellent surface). In addition, the amount of change in the contact angle may not be constant for the purpose of water droplet removal. The necessary width for the region where the contact angle changes continuously is preferable <NUM> or more. When the width is less than <NUM>, there is a concern that the optical characteristics may change abruptly. When the transparent member of the present invention is used for a lens for a vehicle-mounted camera, it is preferable that the contact angle changes in a portion where water droplets are to be removed, that is, in the entire optical effective diameter region of the lens, and it is more preferable that the entire surface of the lens excluding the effective diameter be a region where the contact angle changes, because water droplets may be completely removed from the lens surface.

Specifically, a pattern example of the contact angle change is shown in <FIG> are plan views of front surfaces of lenses which are transparent members. <FIG> varies so that the contact angle decreases continuously from the center of the lens toward the outside (radial direction). In this case, the water droplet may be removed by moving in the radial direction of the lens, which is the same as the existing lens, and may be used as it is without restricting the orientation of the lens. In <FIG>, from one end of the outer periphery of the lens, the contact angle toward the other end facing the one end portion changes so as to be continuously small. In this case, water droplets may be moved to and removed from the other end of the lens. When the lens is tilted, water droplets may be removed in one direction.

Another pattern example of the contact angle change is shown in <FIG>. In <FIG>, the horizontal axis represents the surface position (distance from the start point of the water droplet in the portion where the water droplet moves) when the cross section of the transparent member in the water droplet movement direction is viewed, and the vertical axis represents the contact angle with water.

As a method of forming the surface portion in which the contact angle continuously changes as described above, although described later, since the contact angle depends on the thickness, it is preferable to provide a slope so as to continuously change the thickness of the water-repellent layer constituting the surface portion.

The contact angle may be measured by a known method. For example, the measurement is performed in accordance with the method defined in JIS R3257. The measurement conditions are set to a temperature of <NUM> ± <NUM> and a humidity <NUM> ± <NUM>%. As a specific procedure, about <NUM>µL of water (distilled water) is dropped onto the transparent member, and five points on the transparent member are measured by a solid-liquid interface analyzer (Drop Master <NUM>, manufactured by Kyowa Interface Sciences Co. ), and an average contact angle is obtained from the average of the measured values. The time of the contact angle measurement is <NUM> minute after dropping water.

The transparent member of the present invention comprises a base material provided with a water-repellent layer on the base material. In other words, the water-repellent layer provided on the base material has a surface portion whose contact angle with respect to water varies continuously. The transparent member of the present invention preferably has an antireflection layer formed by laminating a low refractive index layer and a high refractive index layer between a base material and a water-repellent layer. As a preferred configuration of the transparent member of the present invention, as shown in <FIG>, it is a configuration in which an antireflection layer <NUM> and a water-repellent layer <NUM> are provided on a base material <NUM> in this order from the side of the base material <NUM>. The surface side of the water-repellent layer <NUM> is a side in contact with air.

Examples of the base material include glasses and resins. Examples of the resin are a polycarbonate resin and a cycloolefin resin.

The water-repellent layer is provided on the base material and has a surface portion whose contact angle with respect to water varies continuously. In other words, since the contact angle with respect to water depends on the thickness, the thickness of the water-repellent layer having a surface portion changes continuously. Further, it is preferable that the surface roughness of the water-repellent layer, which is the surface portion, changes continuously.

When, for example, a fluoride is used as a constituent material of the water-repellent layer, the contact angle of the water-repellent layer with respect to water is preferably within a range of not less than a contact angle to water of the base material and not more than <NUM>°. In order to achieve such a contact angle, it is preferable that the thickness of the water-repellent layer located at the center of the base material is <NUM>, for example, the thickness of the water-repellent layer is formed to be continuously thin in the radial direction of the base material, and the thickness of the water-repellent layer on the end portion of the base material is formed to be <NUM>. The thickness of the center of the water-repellent layer is preferably within a range of <NUM> to <NUM>, and the thickness of the water-repellent layer on the radial end side is preferably within a range of <NUM> to <NUM> in view of sufficiently securing the water-repellent performance.

The arithmetic average roughness Ra of the surface of the water-repellent layer preferably changes continuously within a range of <NUM> to <NUM> in terms of good water droplet removal. In order to obtain such a surface roughness, it may be formed by, for example, etching, or blasting, which will be described later. The arithmetic average roughness, according to JIS B <NUM>:<NUM>, is a value measured using AFM (atomic force microscopy). Specifically, Dimension Icon (manufactured by Bruker Co. ) was used, and the measuring area was set to <NUM> x <NUM>.

As a constituent material of the water-repellent layer, a fluoride is preferable because it is easy to adjust the contact angle with respect to water, and it is particularly easy to secure a high contact angle. Examples of the fluoride include a fluororesin material. A commercially available products is preferably SURFCLEAR <NUM> (SC-<NUM>) in a tablet form (Canon Optron, Inc. In addition, it may be in a liquid form other than the tablet shape.

The antireflection layer preferably has a multilayer structure in which a high refractive index layer and a low refractive index layer are alternately stacked. The high refractive index layer according to the present invention is a layer having a refractive index higher than that of the base material, and the low refractive index layer according to the present invention is a layer having a refractive index lower than that of the base material. The refractive index of the high refractive index with respect to the wavelength of <NUM> is preferably within a range of <NUM> to <NUM>, and the refractive index with respect to the wavelength of <NUM> of the low refractive index is preferably within a range of <NUM> to <NUM>.

As a material used for the antireflection layer according to the present invention, a dielectric material is preferably used. Suitable examples thereof are oxides of Ti, Ta, Nb, Zr, Ce, La, Al, Si, and Hf, and oxidized compounds combining these compounds. By stacking multiple layers of different dielectric materials, it is possible to add a function of reducing the reflectivity of the entire visible range.

Although the number of laminated layers depends on the required optical performance, it is preferable that the reflectivity of the entire visible range be reduced by laminating approximately <NUM> to <NUM> layers, and that the upper limit number be <NUM> layers or less in view of preventing the film from being peeled off due to an increase in the stress of the film.

As a specific configuration of the antireflection layer according to the present invention, it is preferable that a low refractive index layer, a high refractive index layer, a low refractive index layer, a high refractive index layer, and a low refractive index layer are sequentially arranged from the base material side. It is preferable that a water-repellent layer is provided on the low refractive index layer of the uppermost layer of the antireflection layer, but it is not limited to these layer configurations.

The low index layer is composed of a material having a lower index than the base material, and is preferable, for example, SiO<NUM>, or a mixture of SiO<NUM> and Al<NUM>O<NUM>. In particular, it is preferable to provide a layer made of SiO<NUM> directly below the water-repellent layer in terms of strong bonding between SiO<NUM> and the fluoride in the water-repellent layer.

The low refractive index layer may be formed on the base material by a known method such as a vacuum deposition method, a sputtering method, or an ion plating method, but it is particularly preferable to form the low refractive index layer by a vacuum deposition method. In addition, IAD (Ion Assisted Deposition) (hereinafter, simply referred to as "IAD") may be used in the vacuum deposition method, whereby scratch resistance is improved.

It is preferable that the high refractive index layer is made of a material having a higher refractive index than the base material, and it is, for example, a mixture of an oxide of Ta and an oxide of Ti, or otherwise, an oxide of Ti, an oxide of Ta, a mixture of an oxide of La and an oxide of Ti. Commercially available products of oxides of Ta and oxides of Ti (Ta<NUM>O + TiO<NUM>) include OA-<NUM> (manufactured by Canon Optron, Inc.

The high refractive index layer may be formed on the base material by a known method such as a vacuum deposition method, a sputtering method, or an ion plating method, but it is particularly preferable to form the high refractive index layer by a vacuum deposition method. In addition, in the vacuum deposition method, IAD may be used, which improves scratch resistance.

The thickness of the antireflection layer (the total thickness when a plurality of layers are stacked) is preferably in the range of <NUM> to <NUM>. When the layer thickness is <NUM> or more, it is possible to exhibit the optical properties of antireflection, when the layer thickness is <NUM> or less, it is possible to prevent the surface deformation due to the layer stress generated by the antireflection layer itself.

The method of manufacturing a transparent member of the present invention includes a step of forming a water-repellent layer by forming a film of a water-repellent material, and in the above-mentioned step, the thickness of the water-repellent layer changes continuously.

In the step of forming the water-repellent layer, the thickness of the water-repellent layer changes continuously because the contact angle of the water-repellent layer with respect to water depends on the thickness of the water repellent layer. In addition to controlling the thickness of the water-repellent layer as described above, the water-repellent layer may be formed so that the surface roughness of the water-repellent layer changes continuously, without controlling the thickness of the water-repellent layer. As a means for forming the water-repellent layer so as to continuously change its thickness, for example, when coating a water-repellent material with a mask plate, the thickness may be inclined (film thickness gradient) by using vignetting. In this case, as will be described later, it is preferable to use a vacuum deposition method. In addition, a mask plate having a different opening area depending on the position may be disposed in front of the base material to coat the water-repellent material, thereby providing a film thickness gradient. In this case, it is preferable to use a vacuum deposition method or a spray method. In addition, by forming a mask material on the uniform water-repellent layer with an inclination and etching it, it is also possible to form the water-repellent layer so that the thickness thereof changes continuously.

On the other hand, as a means for forming the water-repellent layer so as to continuously change the surface roughness, an etching method or a blasting method may be used. Specifically, the surface roughness may continuously change by forming a fine concavo-convex pattern so that the period and the depth gradually change and performing etching. Further, the surface roughness may continuously change by the blast method so that the injection amount and the speed are gradually changed. Incidentally, in addition to changing the thickness and surface roughness of the water-repellent layer, as a means for continuously changing the contact angle of the water repellent layer, the contact angle may be reduced by irradiating oxygen plasma or ozone. Therefore, by irradiating while changing the irradiation intensity, the inclination of the contact angle may be created.

In the following, a method of forming a water-repellent layer having a film thickness gradient using vignetting in a vacuum deposition method will be described.

A film-forming method using the vacuum deposition method will be described below together with a description of a vacuum deposition apparatus. As shown in <FIG>, the vacuum deposition apparatus <NUM> according to the present invention includes a chamber <NUM>, a dome <NUM>, and a monitor system <NUM>.

At the bottom of the chamber <NUM>, a plurality of evaporation sources <NUM> are disposed. Here, as the evaporation source <NUM>, <NUM> evaporation sources 6a and 6b are shown, but the number of evaporation sources <NUM> may be <NUM> or <NUM> or more. By heating and evaporating a film-forming material (e.g., a water-repellent material) of the evaporation source <NUM> and adhering the film-forming material to a base material <NUM> (e.g., a glass plate) installed in the chamber <NUM>, a layer <NUM> (e.g., a water-repellent layer) made of a film-forming material (see <FIG>) is formed on the base material <NUM>. As the heating method when evaporating the film-forming material in each evaporation source <NUM>, there are resistance heating, electron beam heating, high-frequency induction heating, or laser beam heating. Any types may be used. The chamber <NUM> is provided with a vacuum evacuation system (not shown), by which the interior of the chamber <NUM> is evacuated.

Incidentally, the mask plate <NUM> is provided in the chamber <NUM>, and the details thereof will be described later.

The dome <NUM> holds at least one holder <NUM> for holding the base material <NUM> and the mask plate <NUM> (see <FIG>), and it is also called a vapor deposition umbrella. The dome <NUM> has an arc-shaped cross section and has a rotationally symmetrical shape that rotates about an axis AX that passes through the center of the chord connecting both ends of the arc and is perpendicular to the chord. When the dome <NUM> rotates about the axis AX at a certain speed, for example, the base material <NUM> and the mask plate <NUM> held by the dome <NUM> via the holder <NUM> revolve around the axis AX at a constant speed.

The dome <NUM> may hold a plurality of holders <NUM> side by side in the rotation radial direction (revolving radial direction) and the rotation direction (revolving direction). This makes it possible to simultaneously form a film on the plurality of base materials <NUM> held by the plurality of holders <NUM>, thereby improving the manufacturing efficiency of the optical element.

The monitoring system <NUM> monitors the characteristics of the layers formed on the base material <NUM> by monitoring the layers that evaporate from the evaporation sources <NUM> and adhere to the monitoring system <NUM> during vacuum deposition. By this monitoring system <NUM>, the optical characteristics of the layer to be deposited on the base material <NUM> are monitored. The optical properties (e.g., transmittance, reflectance, and optical layer thickness) may be grasped. The monitoring system <NUM> may also include a quartz layer thickness monitor to monitor the physical layer thickness of the layer deposited on the base material <NUM>. The monitoring system <NUM> also functions as a control unit for controlling switching of ON/OFF of the plurality of evaporation sources <NUM> in accordance with the monitoring result of the layer.

<FIG> is an enlarged cross-sectional view showing a portion A of <FIG>. The holder <NUM> is a holding member for holding the base material <NUM> and the mask plate <NUM>. The holder <NUM> has a holding plate <NUM> for holding the base material <NUM> and a shaft <NUM>. The shaft <NUM> penetrates a hole (not shown) provided in the holding plate <NUM> and a hole (not shown) provided in the mask plate <NUM>. Holding plate <NUM> is fixed to the shaft <NUM> sandwiched by the nuts <NUM> and <NUM>. Mask plate <NUM> is fixed to the shaft <NUM> sandwiched by the nuts <NUM> and <NUM>.

By turning nuts <NUM> and <NUM> or nuts <NUM> and <NUM>, it is possible to move the mask plate <NUM> relative to the base material <NUM> in the axial direction of the shaft <NUM>. This makes it possible to adjust the distance T between the base material <NUM> and the mask plate <NUM>. Incidentally, when the position of the mask plate <NUM> with respect to the base material <NUM> by the holder <NUM> is once fixed (the gap T is set to a predetermined value), in the film formation (film forming step), the position of the mask plate <NUM> (i.e., the gap T) is not changed.

Next, the details of the mask plate <NUM> will be described.

The mask plate <NUM> is located on the side of the plurality of evaporation sources <NUM> with respect to the base material <NUM>, and revolves together with the base material <NUM> in a state where a gap T is formed between the mask plate <NUM> and a part of the base material <NUM>. It is held in the chamber <NUM> by the holder <NUM> described above. <FIG> is a plan view of each of the base materials <NUM> and the mask plate <NUM> corresponding to any base material <NUM> when the holder <NUM> holding the base material <NUM> and the mask plate <NUM> is aligned in the revolving radial direction and in the revolving direction and held on the dome <NUM>. In order to clarify the shape of the mask plate <NUM>, in <FIG>, hatching is conveniently attached to the mask plate <NUM> (the same applies to other drawings). As shown in the figure, the width of the revolving direction of the mask plate <NUM> is constant in the revolving radial direction, the planar shape of the mask plate <NUM> has a rectangular.

By holding the mask plate <NUM> in the chamber <NUM> as described above, a film thickness gradient corresponding to the gap T may be imparted to the layer <NUM> (water-repellent layer) made of the film-forming material which evaporates from the evaporation source <NUM> and adheres on the base material <NUM>. This point will be described in more detail as follows.

<FIG> schematically show the principle that the mask plate <NUM> imparts a film thickness gradient to the layer <NUM> (water-repellent layer) formed on the base material <NUM>. When the mask plate <NUM> is positioned on the side of the evaporation source <NUM> with respect to the base material <NUM>, at each position in the revolving direction of the base material <NUM> and the mask plate <NUM>, a part of the film-forming material from each evaporation source <NUM> toward the base material <NUM> is shielded by the mask plate <NUM>. At this time, when the gap T between the base <NUM> and the mask plate <NUM> is narrow (the gap T at this time is Ta), the film-forming material directed toward the base <NUM> hardly enters the depth (up to the end portion of the base <NUM>) between the base <NUM> and the mask plate <NUM>. Therefore, the film thickness gradient of the layer <NUM> formed on the base material <NUM> becomes steep (see 7A).

On the other hand, as shown in the drawing 7B, when the gap T between the base material <NUM> and the mask plate <NUM> is wide (Tb > Ta, when the gap T at this time is Tb), the film-forming material directed toward the base material <NUM> without being shielded by the mask plate <NUM> easily enters the depth between the base material <NUM> and the mask plate <NUM>. Therefore, the film thickness gradient of the layer <NUM> formed on the base material <NUM> becomes gradual.

Therefore, by arranging the mask plate <NUM> with a part of the base material <NUM> and the gap T therebetween, it is possible to impart a film thickness gradient corresponding to the gap T to the layer <NUM> formed on the base material <NUM>.

In the present invention, a water-repellent material is vapor-deposited on a base material by using the above-described vapor deposition apparatus, thereby forming a water-repellent layer with a film thickness gradient which is imparted by eclipsing with a mask plate.

In the present invention, the gap T between the base material <NUM> and the mask plate <NUM> is preferably within a range of <NUM> to <NUM>, and more preferably within a range of <NUM> to <NUM>. When the optical member is large, it is preferable that the region of the film thickness gradient be large, and therefore, it is preferable that the gap T is also large. When the optical member is small, the region of the film thickness gradient may be small, and therefore, it is preferable to appropriately set the gap T.

Incidentally, the mask plate <NUM>, in <FIG>, is held at one end side of the holder <NUM>, and has been arranged so as to cover the half surface of the base material. It is not limited to this. For example, as shown in <FIG>, a mask plate 12A having a hole formed in the center by a punch or a drill may be used, and the mask plate 12A may be configured to hold at both ends of the holder (not shown). In this case, a part of the film-forming material from the evaporation source <NUM> toward the base <NUM> is eclipsed by the mask plate <NUM>. At this time, since the portion excluding the center portion of the base material <NUM> (the end portion side of the base material <NUM>) is covered with the mask plate <NUM>, a film thickness gradient is formed so that the center portion of the base material <NUM> is thickest and the thickness gradually decreases toward the end portion side of the base material <NUM>. Similarly, when the mask plate 12A having a hole formed in the center portion is used, the film thickness gradient becomes steep when the gap T between the base material <NUM> and the mask plate <NUM> is narrow, and the film thickness gradient becomes gentle when the gap T is wide. Further, the size (opening area) of the hole formed in the central portion may be appropriately changed in accordance with the size of the region of the film thickness gradient in which the water-repellent layer is to be formed. Specifically, when a base material having a diameter of <NUM> is used, it is preferable to use a mask plate in which a hole having a diameter of <NUM> to <NUM> is formed in the center portion. The shape of the hole may not be a perfect circle, and irregularities may be formed on the peripheral surface that forms the hole.

In the coating method according to the present invention, it is preferable to coat a water-repellent material so that the thickness of the water-repellent layer continuously changes on the base material. Examples of the coating method include a spin coating, a dip coating, and a spray method. Among them, the spray method is preferable in that the thickness of the water-repellent layer is easily formed with continuously inclined thickness.

The spray method according to the present invention is a method of coating a water-repellent material by spraying. The thickness of the water-repellent layer may be arbitrarily controlled by the irradiation time of the spray. Further, similarly to the vapor deposition method, the thickness may be continuously changed by a method using a mask at the time of spraying.

Prior to the step of forming the water-repellent layer, a step of forming an antireflection layer on a base material may be provided. In the step of forming the antireflection layer, a film may be formed on the base material by a known method such as a vacuum deposition method, a sputtering method, or an ion plating method, but it is particularly preferable to form the film by a vacuum deposition method. In addition, in the vacuum deposition method, IAD may be used, which improves scratch resistance. In the case of using IAD, an ion gun may be provided in the above-described vapor deposition apparatus, and the drive of the ion gun may be turned on at the time of film formation to form a film.

The transparent member of the present invention is used in an optical component for vehicle use or outdoor use. Examples of the vehicle-mounted optical component of the present invention include a lens unit mounted on a vehicle-mounted camera. The "vehicle-mounted camera" is a camera installed on the outer side of the vehicle body of an automobile, and it is installed on the rear portion of the vehicle body and used for the rear confirmation, or it is installed on the front portion of the vehicle body and used for the front confirmation or the side confirmation, or used for the confirmation of the distance from the front vehicle. Such a lens unit for a vehicle-mounted camera is constituted by a plurality of lenses, in particular, an object-side lens disposed on the object side, and an image-side lens group disposed on the image side. The image-side lens group includes a plurality of lenses and an aperture provided between the lenses. Among such a plurality of lenses, the object-side lens has an exposed surface exposed to the outside air, and the transparent member of the present invention is preferably used as a lens having this exposed surface.

Examples of the optical component for outdoor use include a surveillance camera of an outdoor installed type, and the transparent member of the present invention is preferably used as a lens having an exposed surface exposed to the outside air among lenses constituting the surveillance camera.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

As a manufacturing example to give a surface portion where the contact angle changes continuously, a method in which a water-repellent material is vapor-deposited by a vacuum deposition method and the thickness of the water-repellent layer is inclined was adopted.

The above base material was installed in a vacuum deposition apparatus, then, a mask plate was disposed between the evaporation source and the base material so as to cover half of the base material and to be parallel to the base material, and the base material was eclipsed with the mask plate, whereby the thickness of the water-repellent layer on the base material after vapor-deposition changed continuously. In addition, in order to stabilize the water-repellent layer, the film was left at room temperature for more than half a day after film formation. When the distance between the base material and the mask plate was <NUM> and <NUM>, film formation was performed, respectively, to obtain two transparent members having a water-repellent layer formed on the base material. When <NUM>µL of water droplets was attached to each of the obtained transparent members, it was confirmed as follows that the water droplets moved from the portion where the mask plate was not disposed (the portion where the thickness of the water-repellent layer was thick) toward the portion where the mask plate was disposed (the portion where the thickness of the water-repellent layer was thin). At this time, it was confirmed that the moving speed of the water droplet was higher when the distance between the base material and the mask plate was smaller (<NUM>) than when the distance between the base material and the mask plate was larger (<NUM>). Further, it was confirmed that the moving distance of the water droplet was longer when the distance between the base material and the mask plate was larger (<NUM>) than when the distance between the base material and the mask plate was smaller (<NUM>). The thickness of the water-repellent layer of each transparent member was confirmed. When the distance between the base material and the mask plate was <NUM> and <NUM>, the lengths in the moving directions of the water droplets in the regions where a continuous film thickness gradient of <NUM> to <NUM> was formed were found to be <NUM> and <NUM>, respectively. The contact angle in the region where the thickness of the water-repellent layer was <NUM> was <NUM>°, and the contact angle in the region where the thickness was <NUM> was <NUM>°.

A mask plate in which holes were formed was placed between the base material and the evaporation source so that the holes were located at the center of the base material, and a film was formed in the same manner as in Example <NUM>. In addition, a convex lens (diameter <NUM>) was used, the diameter of the hole of the mask plate was set to <NUM>, and the distance between the base material and the mask plate was set to <NUM>. For the obtained transparent member, when the water droplets adhered, it was confirmed that water droplets moved from the portion where the hole portion of the mask plate was arranged (center portion of the base material) towards the radial direction of the portion where the mask plate was arranged. In addition, it was confirmed that the water droplet moved in the outward direction of the base material in the majority of the base material.

In Example <NUM> and Example <NUM>, experiments were conducted on a transparent member in which a water-repellent layer was formed on a base material, but it was confirmed that water droplets moved in the same manner when an antireflection layer (a laminated layer in which SiO<NUM> (low refractive index layer), OA-<NUM> (high refractive index layer), SiO<NUM> (low refractive index layer), OA-<NUM> (high refractive index layer), and SiO<NUM> (low refractive index layer)) was formed in this order from the base material side on the base material, and a water-repellent layer was formed on the antireflection layer in the same manner as in Examples <NUM> and <NUM>.

Claim 1:
A transparent member comprising a base material provided with a water-repellent layer on the base material, wherein the transparent member has a surface portion whose contact angle to water changes continuously,
wherein the water-repellent layer includes said surface portion,
characterized in that
the thickness of the water-repellent layer changes continuously.