阅读说明：本技术 光学元件及其制造方法 (Optical element and method for manufacturing the same ) 是由 内山博一 桥本昌树 板津信夫 于 2020-03-10 设计创作，主要内容包括：提供具有基材和形成于其上的层叠被膜而成的光学元件的制造方法。在本发明的制造方法中,包括：形成层叠被膜的光学多层部的多层形成工序；以及形成层叠被膜的最表面部的最表面形成工序,在多层形成工序与所述最表面形成工序之间,使用于形成所述层叠被膜的压力条件不连续。另外,在最表面形成工序中,在含氟化合物层的形成之前形成含氧化硅层。(Provided is a method for manufacturing an optical element having a base material and a laminated film formed thereon. The manufacturing method of the present invention includes: a multilayer forming step of forming an optical multilayer portion of the laminated coating; and an outermost surface forming step of forming an outermost surface portion of the laminated film, wherein a pressure condition for forming the laminated film is discontinued between the multilayer forming step and the outermost surface forming step. In the outermost surface forming step, the silicon oxide-containing layer is formed before the formation of the fluorine-containing compound layer.)

1. A method for manufacturing an optical element comprising a base material and a laminated film formed on the base material, wherein,

comprising a multilayer forming step of forming an optically multi-layer portion of the laminated coating film and an outermost surface forming step of forming an outermost surface portion of the laminated coating film,

discontinuing pressure conditions for forming the laminated film between the multilayer forming step and the outermost surface forming step,

the outermost surface forming step includes forming a silicon oxide-containing layer before forming the fluorine-containing compound layer.

2. The method for manufacturing an optical element according to claim 1, wherein a mixed layer in which a fluorine compound and silicon oxide are mixed is formed between the fluorine compound-containing layer and the silicon oxide-containing layer.

3. The method of manufacturing an optical element according to claim 1 or 2, wherein both the multilayer forming step and the outermost surface forming step are performed under a vacuum low pressure condition, and the vacuum low pressure condition is temporarily released between the multilayer forming step and the outermost surface forming step.

4. The method for manufacturing an optical element according to any one of claims 1 to 3, wherein the fluorine-containing compound layer is formed as a layer having surface irregularities.

5. An optical element comprising a base material and a laminated film formed on the base material,

the laminated coating film is composed of an optical multi-layer part and an outermost surface part,

the outermost surface portion has a silicon oxide-containing layer and a fluorine-containing compound layer, and the fluorine-containing compound layer is formed as a layer having surface irregularities.

6. The optical element according to claim 5, wherein a mixed layer in which a fluorine compound and silicon oxide are mixed is present between the fluorine compound-containing layer and the silicon oxide-containing layer.

7. The optical element according to claim 5 or 6, wherein the difference in thickness of the surface irregularities is 10nm or more and 80nm or less.

8. The optical element according to any one of claims 5 to 7, wherein a convex portion occupancy rate of the surface irregularities in the fluorine-containing compound layer is 3% or more and 20% or less.

9. The optical element according to any one of claims 5 to 8, wherein in a sectional image of the optical element, an interface is observed between the optical multi-layer portion and the outermost surface portion.

10. The optical element according to any one of claims 5 to 9, wherein the fluorine compound contained in the fluorine-containing compound layer is a compound having a perfluoroalkyl ether group.

11. The optical element according to any one of claims 5 to 10, wherein the minimum thickness of the fluorine-containing compound layer is 3nm or more and 25nm or less.

12. The optical element according to any one of claims 5 to 11, wherein the optical multi-layer portion is formed by alternately laminating a high refractive index layer having a relatively high refractive index and a low refractive index layer having a relatively low refractive index.

13. The optical element according to any one of claims 5 to 12, wherein the optically multilayer portion is formed by laminating 4 or more layers.

Technical Field

The present invention relates to an optical element and a method for manufacturing the same. And more particularly to a method of manufacturing an optical element having more suitable surface characteristics, and to an optical element obtained by such a manufacturing method.

Background

Patent document 1 discloses an optical element having weather resistance, which is provided with a layer containing a large number of fluorine atoms on the surface. Patent document 2 discloses an optical element having a hydrophobic film containing fluorine atoms on a glass lens, and having improved abrasion resistance of the hydrophobic film.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2005/292340

Patent document 2: japanese patent laid-open No. 2018/159892

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide an optical element having excellent weather resistance and abrasion resistance.

Means for solving the problems

The manufacturing method of the present invention is a manufacturing method of an optical element having a base material and a laminated film formed on the base material,

the method for manufacturing an optical element includes a multilayer forming step of forming an optical multi-layer portion of a laminated coating film and an outermost surface forming step of forming an outermost surface portion of the laminated coating film,

between the multilayer forming step and the outermost surface forming step, the pressure conditions for forming the laminated film are not continuous,

in the outermost surface forming step, the silicon oxide-containing layer is formed before the fluorine-containing compound layer is formed.

The optical element of the present invention comprises a base material and a laminated film formed on the base material,

the laminated coating film is composed of an optical multi-layer part and an outermost surface part,

the outermost surface portion has a silicon oxide-containing layer and a fluorine-containing compound layer, and the fluorine-containing compound layer is formed as a layer having surface irregularities.

ADVANTAGEOUS EFFECTS OF INVENTION

In the present invention, an optical element having both weather resistance and abrasion resistance is provided. More specifically, the optical element having an optical multilayer portion and a silicon oxide-containing layer provided prior to the fluorine-containing compound layer under discontinuous pressure conditions as an outermost surface portion brings excellent weather resistance and abrasion resistance at the same time.

Drawings

Fig. 1 is a cross-sectional view schematically showing an optical element according to an embodiment of the present invention.

Fig. 2 (a) to 2 (c) are cross-sectional views schematically showing ductility of the fluorine-containing compound layer according to the embodiment of the present invention.

Fig. 3 (a) and 3 (b) are schematic cross-sectional views showing a fluorochemical layer according to an embodiment of the present invention.

Fig. 4 is a schematic cross-sectional view mainly showing the outermost surface portion of the optical element and the vicinity thereof according to one embodiment of the present invention.

Fig. 5 is a schematic cross-sectional view mainly showing the outermost surface portion of the optical element (optical element of example 1) according to one embodiment of the present invention and the vicinity thereof.

Fig. 6 (a) to 6 (c) are cross-sectional views schematically showing various embodiments of the optical element of the present invention.

Fig. 7 is a graph showing the results of the abrasion resistance test of example 1 and comparative example 1.

Fig. 8 is a graph showing the results of the weather resistance test of example 1 and comparative example 1.

Fig. 9 is a graph showing the results of the wear resistance test in examples 1 and 2.

Fig. 10 is a graph showing the results of the weather resistance test in examples 1 and 2.

Fig. 11 is a cross-sectional TEM image of the optical element taken by a Transmission Electron Microscope (TEM) at a magnification of 500000 times.

Fig. 12 is a cross-sectional TEM image of the optical element taken by a Transmission Electron Microscope (TEM) at a magnification of 1000000 times.

Fig. 13 is a surface image of the optical element of example 1 of the present invention taken by an optical microscope.

Detailed Description

[ findings on the basis of the present invention, etc. ]

Conventionally, optical elements formed of a resin material, a glass material, or the like have been used for various purposes. For example, the optical element is used as an optical fiber, a lens, or the like.

In recent years, optical elements have been used in the field of optical lenses for monitoring systems for disaster prevention, crime prevention, and the like, and exterior applications such as lenses for vehicle-mounted cameras, and the like.

In an optical element used for an exterior lens, it is important to have desired surface characteristics.

The present inventors have noted that problems to be overcome still remain in optical elements proposed in the past, and have found the necessity of taking countermeasures for this. Specifically, the present inventors found that the following problems exist.

There is known a technique of applying a coating film exhibiting various properties to a base material of an optical element by a coating method, a vapor deposition method, or the like. For example, an optical element having excellent weather resistance by having a layer containing a large amount of fluorine atoms on the surface thereof has been proposed. Further, an optical element having a glass lens and a hydrophobic film containing fluorine atoms and having improved abrasion resistance of the hydrophobic film has been proposed.

However, the hydrophobic film described above merely improves abrasion resistance against hydrophobicity, and does not have excellent weather resistance (particularly light resistance). Therefore, when the lens is used in a severe use environment for exterior applications (for example, a lens for an in-vehicle camera), sufficient performance may not be obtained.

The present inventors have attempted to solve the above-described problems by dealing with the extension in a new direction, rather than dealing with the extension in the related art. As a result, the invention of an optical element having both of the desired weather resistance and abrasion resistance has been completed.

The optical element of the present invention will be described in more detail below. In some cases, the detailed description may be omitted. For example, detailed descriptions of already known matters or repetitive descriptions of substantially the same configuration may be omitted. This is to avoid unnecessarily lengthy descriptions that would be apparent to one skilled in the art.

The drawings and the following description are provided to enable those skilled in the art to fully understand the present invention, and are not intended to limit the subject matter described in the claims. It should be noted that the various elements in the drawings are merely schematically and exemplarily illustrated for understanding the optical element of the present invention and the manufacturing method thereof, and the appearance, the size ratio, and the like may be different from those of the actual object.

In the present invention, the "optical element" means a member for transmitting light. Thus, the optical element is, for example, a lens, a prism or a mirror, and further, may also be a window article or the like associated with light transmission.

In the present specification, the "cross section" is based on a cross section obtained by cutting along the thickness direction of the optical element. In other words, the schematic diagram in a cross section taken along the thickness of the optical element corresponds to a "cross section". Typically, the "thickness direction of the optical element" may correspond to the light transmission direction in the optical element.

[ method for producing optical element of the present invention ]

The manufacturing method of the present invention is a method for manufacturing an optical element including a base material and a laminated film formed thereon. The manufacturing method is characterized at least in terms of pressure conditions for forming the laminated film.

The manufacturing method of the present invention includes a multilayer forming step and an outermost surface forming step. The multilayer forming step is a step for forming the optical multilayer portion of the laminated coating, and the outermost surface forming step is a step for forming the outermost surface portion of the laminated coating. In fig. 1, a cross-section of an optical element 100 is illustrated. The optical element 100 has an optical multi-layer portion 23 and an outermost surface portion 22 thereon as a laminated coating film 20. The formation of the optical multi-layer portion 23 is performed as a multi-layer forming step, and the formation of the outermost surface portion 22 is performed as an outermost surface forming step. In the manufacturing method of the present invention, the pressure conditions for forming the laminated film are not continuous between the multilayer forming step and the outermost surface forming step.

More specifically, after the formation of the optical multi-layer portion of the laminated film in the multi-layer forming step, the outermost surface portion of the laminated film is formed in the outermost surface forming step, and the pressure condition is not continuously maintained when the transition from the multi-layer forming step to the outermost surface forming step is made. For example, when the laminated film is formed under low pressure in the multilayer forming step and then is formed under low pressure in the outermost surface forming step, the low pressure condition is temporarily released without continuously maintaining the low pressure condition therebetween. That is, when the laminated film is formed in the outermost surface forming step, the pressure condition is temporarily reset before that.

By discontinuing the pressure conditions, the continuity of the formation of the laminated film can be temporarily cut between the multilayer forming step and the outermost surface forming step. That is, the formation of the laminated film can be once retreated before the outermost surface forming step is performed. For example, in a multilayer forming step of sequentially forming a plurality of layers, the surface may be gradually roughened as the number of layers increases, and when the fluorochemical layer is provided in a state where such surface roughness is present, it is difficult to provide good adhesion to the fluorochemical layer due to the surface roughness. In "discontinuation of pressure conditions", measures to reduce such surface roughness are easily taken. For example, by forming a layer to be thin on a rough surface, the surface roughness can be reduced, and good adhesion to the fluorine-containing compound layer can be provided. Further, by subjecting the surface of the optical multilayer portion of the laminated film to surface modification treatment such as ion cleaning and/or oxygen plasma treatment before the outermost surface forming step, it is also possible to provide higher adhesion between the optical multilayer portion and the outermost surface portion formed thereon.

In the manufacturing method of the present invention, both the multilayer forming process and the outermost surface forming process may be based on a gas phase method. That is, the optical multilayer portion and the outermost surface portion of the coating film may be laminated by a vapor phase method. For example, in the multilayer forming step and the outermost surface forming step, the optically multilayer portion and the outermost surface portion may be formed by a Vapor phase method such as a PVD (Physical Vapor Deposition) method or a CVD (Chemical Vapor Deposition) method. The PVD method is a gas phase method using physical movement of particles in a broad sense, and is a method of forming a layer by temporarily evaporating and vaporizing a layer material by energy such as heat or plasma in a narrow sense. Examples of the PVD method include a vapor deposition method, a sputtering method, an ion plating method, and an MBE (molecular beam epitaxy) method. The CVD method is a gas phase method utilizing a chemical reaction in a broad sense, and is a method of forming a layer by applying heat, light, and/or plasma energy to a layer-constituting material supplied in a gas form to form a decomposed product, a reactant, or an intermediate product of a raw material gas molecule. Examples of the CVD method include a thermal CVD method, an MOCVD (Metal Organic Chemical Vapor Deposition) method, an RF plasma CVD method, an optical CVD method, a laser CVD method, and an LPE (Liquid Phase Epitaxy) method.

In the manufacturing method of the present invention, the multilayer forming step and the outermost surface forming step may be formed by the same method as each other, or may be formed by different methods from each other. Similarly, the formation of each layer of the optical multilayer portion and the outermost surface portion may be performed by the same method for all or a part of the layers, or may be performed by different methods for each layer.

In one embodiment, the multilayer forming step and the outermost surface forming step are based on a vapor deposition method. That is, both the optical multi-layer portion and the outermost surface portion of the laminated coating film can be formed by a vapor deposition method. As the vapor deposition method, for example, a vacuum vapor deposition method, an ion-assisted vapor deposition method, or the like can be used. The vacuum evaporation method is a method of temporarily evaporating a raw material under a vacuum low pressure and then forming a layer as a vapor-deposited film. The ion assisted deposition method is a method in which gas ion irradiation is added at the time of vacuum deposition to form a layer as a deposited film in the same manner as in the vacuum deposition.

When the multilayer forming step and the outermost surface forming step are performed by vapor deposition, the multilayer forming step and the outermost surface forming step may be performed under vacuum and at low pressure. In this case, the vacuum low-pressure condition is not continued between the multilayer forming step and the outermost surface forming step. That is, after the formation of the laminated film is performed under a low vacuum pressure in the multilayer formation step, when the laminated film is formed under a low vacuum pressure also in the outermost surface formation step, the low vacuum pressure condition is temporarily released without continuously maintaining the low vacuum pressure condition therebetween. This makes it possible to temporarily cut off the continuity of the formation of the laminated film between the multilayer formation step and the outermost surface formation step, and to reprocess the formation of the laminated film before the outermost surface formation step is performed. In the present invention, the "vacuum low-pressure condition" means a pressure condition at least lower than atmospheric pressure, and substantially means a low-pressure condition at a level that can be regarded as a vacuum by those skilled in the art who perform a vapor deposition method, as compared with a complete vacuum. In short, the vacuum low pressure condition may be 1.0X 10, which is merely exemplary^-5Pa～1.0×10^-1A pressure around Pa or a pressure lower than Pa. More specifically, the background pressure may be set to 4.0 × 10^-4Pa or less, and the pressure at the time of vapor deposition is 4.0X 10^-4Pa～7.0×10^-2A vacuum low pressure condition such as a pressure condition of about Pa or lower.

In short, the vacuum vapor deposition apparatus used in the multilayer formation process is merely an example, and the sealed state can be temporarily released after the formation of the optical multilayer portion. This makes it possible to discontinue the pressure conditions for forming the laminated film. For example, the surface forming step may be performed by releasing the vacuum low-pressure condition after the formation of the optical multilayer portion, and setting the vacuum low-pressure condition again after passing through the atmospheric pressure condition. In the multilayer forming step and the outermost surface forming step, separate vapor deposition apparatuses may be used by releasing the vacuum. This also makes it possible to discontinue the pressure conditions for forming the laminated film. For example, in the case of using a vacuum vapor deposition apparatus, a multilayer formation step of forming the optical multilayer portion on the substrate may be performed in a 1 st film deposition apparatus, and then an outermost surface formation step of forming the fluorine-containing compound layer and the silicon oxide-containing layer on the optical multilayer portion may be performed in a 2 nd film deposition apparatus different from the 1 st film deposition apparatus. The temperature condition in the multilayer forming step may be 200 ℃ to 350 ℃ from the viewpoint of vaporizing the vapor deposition material in the optical multilayer portion. In addition, the temperature condition in the outermost surface forming step may be 200 ℃ or lower from the viewpoint of weather resistance, abrasion resistance, and the like of the fluorine-containing compound layer. For example, the 2 nd film formation/deposition apparatus may be used without heating.

In the outermost surface forming step of the production method of the present invention, the silicon oxide-containing layer is formed before the fluorine-containing compound layer is formed. In the outermost surface forming step, when the fluorine-containing compound layer and the silicon oxide-containing layer are formed, the silicon oxide-containing layer is formed before the fluorine-containing compound layer. More specifically, after the optical multilayer portion is formed in the multilayer forming step, the pressure conditions are not continued but are reset, whereby the silicon oxide-containing layer and the fluorine-containing compound layer are sequentially formed on the optical multilayer portion in the outermost surface forming step.

The silicon oxide-containing layer formed in the outermost surface forming step may be an additional silicon oxide-containing layer. This is described in detail. For example, in the case where the layer to be formed at the end of the multilayer formation step is a silicon oxide-containing layer (that is, in the case where the outermost layer of the optical multilayer portion is a silicon oxide-containing layer), in the outermost surface formation step, a fluorine-containing compound layer is formed on the silicon oxide-containing layer of the optical multilayer portion through the same or the same silicon oxide-containing layer, without forming the fluorine-containing compound layer. Therefore, the silicon oxide-containing layer formed in the outermost surface forming step can be considered to be a layer added to the silicon oxide-containing layer in the outermost layer of the optical multilayer portion. The "additional silicon oxide-containing layer" may contribute to a reduction of the surface roughness of the optical multilayer portion. That is, in the multilayer forming step of sequentially forming a plurality of layers, the surface may be gradually roughened as the number of layers increases, but in the outermost surface forming step, the surface roughness can be reduced by thinly forming the silicon oxide-containing layer on the roughened surface. More specifically, by thinly forming the "additional silicon oxide-containing layer" so as to fill the recessed portions of the rough surface in the outermost surface forming step, the silicon oxide-containing layer can be provided as a dense film (for example, the surface roughness of Ra >5nm can be reduced to Ra < 2nm or the like by the dense film). Therefore, good adhesion can be provided between the fluorochemical layers formed thereon.

In other words, the optical element obtained through the outermost surface forming step includes the silicon oxide-containing layer provided before the fluorine-containing compound layer under pressure conditions discontinuous from the optical multilayer portion, and therefore, the weather resistance and the abrasion resistance can be improved. For example, the optical element has improved weather resistance such as light resistance, chemical resistance and/or moist heat resistance, or has improved abrasion resistance such as surface friction resistance.

In one embodiment, the hybrid layer is formed in the laminated film in the outermost surface forming step. Specifically, a mixed layer in which a fluorine compound and silicon oxide are mixed is formed between the fluorine compound-containing layer and the silicon oxide-containing layer.

The hybrid layer can be formed by continuing to form the silicon oxide-containing layer and the fluorine-containing compound layer after temporarily resetting the pressure condition. In the case where both the multilayer formation step and the outermost surface formation step are based on the vapor deposition method, the formation of the hybrid layer can be particularly facilitated. The reason is not limited by a particular theory, but is that the fluorine compound component containing the silicon oxide layer functions in such a manner as to appropriately infiltrate the fluorine compound containing layer.

The "mixed layer in which a fluorine compound and silicon oxide are mixed" obtained in the outermost surface forming step can make the adhesion between the fluorine-containing compound layer and the silicon oxide-containing layer stronger, and therefore, it is easy to maintain, for a longer period of time, light resistance that suppresses a decrease in characteristics due to light such as ultraviolet light, visible light, and/or infrared light, and abrasion resistance that has resistance to friction due to external elements.

In one embodiment, the fluorochemical layer is formed as a "layer having surface irregularities". That is, when the fluorochemical layer constitutes the outermost layer of the laminated coating film of the optical element, the surface of the outermost layer is obtained as an uneven surface.

In the present invention, the fluorochemical layer corresponds to a layer provided after the silicon oxide-containing layer is formed under pressure conditions discontinuous from the optical multilayer portion, and the surface irregularities of such a fluorochemical layer can contribute particularly effectively to abrasion resistance. Although not limited by a particular theory, the abrasion resistance in the present invention is due to the ductility of the surface irregularities in the fluorochemical layer. As will be described in detail later, the fluorine-containing compound layer having irregularities can follow the frictional force applied to the surface thereof, and the abrasion of the layer can be appropriately prevented. In particular, if the layer has irregularities, when the surface of the layer receives a frictional force, the portion having a large layer thickness can be deformed so as to compensate the portion having a small layer thickness, and good durability can be provided for the frictional force. Therefore, an optical element including a fluorochemical layer having surface irregularities exhibits more excellent abrasion resistance.

The present inventors have found that such surface irregularities can be suitably obtained by forming a silicon oxide-containing layer under pressure conditions discontinuous with those of the optical multi-layer portion and then forming a fluorine-containing compound layer. That is, by successively forming the silicon oxide-containing layer and the fluorine-containing compound layer after the pressure condition is temporarily reset, the fluorine-containing compound layer having appropriate surface irregularities in terms of wear resistance can be easily obtained.

[ optical element of the present invention ]

The optical element of the present invention has a fluorochemical layer on the outermost surface, and has at least the features related to the fluorochemical layer. The optical element of the present invention can be obtained by the above-described production method.

More specifically, the optical element of the present invention includes a substrate and a laminated film formed thereon, and the laminated film includes an optical multilayer portion and an outermost surface portion. The outermost surface portion has a silicon oxide-containing layer and a fluorine-containing compound layer, and the fluorine-containing compound layer on the outermost surface portion is formed as a layer having surface irregularities. The fluorochemical layer has a low coefficient of friction and can contribute to wear resistance.

In the laminated film formed on the optical element, "outermost portion" in the present invention means the outermost surface and its peripheral portion (i.e., the outermost layer and at least 1 layer located therebelow, preferably the outermost layer and 1 or 2 layers therebelow). In the illustrated exemplary embodiment, the fluorochemical layer 22A corresponds to the outermost layer of the laminated film 20 in the cross-section of the optical element 100 shown in fig. 1.

The fluorine-containing compound layer may have ductility due to its surface irregularities. More specifically, when a frictional force is applied to the fluorochemical layer, the surface irregularities can be deformed to follow the frictional force, and abrasion of the layer can be prevented appropriately. In particular, when the uneven fluorochemical layer is deformed on the surface thereof following the frictional force, the thick portion of the layer can compensate the thin portion of the layer, and the layer can exhibit excellent durability against the friction.

In one embodiment, the difference in thickness between the surface irregularities of the fluorochemical layer is 10nm or more and 80nm or less. If the difference in thickness is 10nm or more, the portion having a large thickness is easily deformed so as to compensate the portion having a small thickness, and abrasion of the layer can be more appropriately prevented. In addition, if the difference in thickness is 80nm or less, unintended surface reflection of light is easily suppressed, and the transparency of the optical element is easily maintained well. In other words, if the thickness difference is less than 10nm, it becomes difficult for the thick layer portion to compensate for the thin layer portion, and the layer surface portion tends to follow the rubbing. Moreover, if the difference in thickness is greater than 80nm, surface reflection of unintended light is easily generated. The difference in the thickness of the surface irregularities of the fluorochemical layer is preferably 10nm or more and 50nm or less, for example, 20nm or more and 40nm or less, or 20nm or more and 30nm or less.

The "surface irregularity"/"irregularity" in the present invention broadly means an optical element having undulations (i.e., projections) and depressions (i.e., recesses) in the same layer, but does not contribute to the directivity of light like a fresnel lens. That is, the surface irregularities of the fluorochemical layer do not generally have a regular or constant cross-sectional shape, and also do not generally have an angular cross-sectional shape. Further, since the surface irregularities do not correspond to optical elements such as grooves provided in the fresnel lens, the surface irregularities are randomly distributed in the surface direction of the fluorochemical layer. Further, the convex portions and/or concave portions are preferably curved in a microscopic view as a cross-sectional profile of the surface irregularities. Also, similarly, if the cross-sectional profile is microscopically captured, the tip portion of the convex portion and/or the bottom-most portion of the concave portion may be rounded from the viewpoint of improving wear resistance. Such curved surface irregularities can contribute more effectively to the wear resistance resulting from the follow-up deformation.

As is clear from the above, the surface irregularities of the fluorochemical layer may be referred to as "curved surface irregularities", "irregular irregularities", "random surface irregularities", and the like in the present invention. In a narrow sense, "surface unevenness"/"unevenness" in the present invention means that the difference in thickness in the same layer is, for example, 10nm or more. The "thickness difference within the same layer" can be determined from the following image: a cross-sectional direction cross section was cut out at an acceleration voltage of 10 to 40KV by a focused ion beam apparatus (model FB2200 manufactured by Hitachi, Ltd.), and an image was obtained at an acceleration voltage of 200KV by a Transmission Electron Microscope (TEM) (model JEM-2800 manufactured by JEOL).

In the present invention, the difference in thickness of the surface irregularities of the fluorochemical layer is preferably 10nm or more and 80nm or less, which can be determined from a cross-sectional TEM image of an arbitrary site. In the present invention, the phrase "the difference in thickness between the surface irregularities is 10nm to 80 nm" means that the difference between the maximum thickness and the minimum thickness of the fluorine-containing compound layer in a cross-sectional TEM image of an arbitrary portion of the layer is in the range of 10nm to 80 nm. For example, from a cross-sectional TEM image having a width of 3 μm or less (as an example, an image of a portion having a width of about 300nm is taken), the thicknesses of the portion having the largest layer thickness and the portion having the smallest layer thickness in the fluorochemical layer are determined as the maximum thickness and the minimum thickness, respectively, and the difference between the maximum thickness and the minimum thickness is calculated. This measurement is performed on any 5 or more cross-sectional TEM images, and the thickness difference may be in the range of 10nm to 80nm in all the measurements.

As is clear from the exemplary embodiment shown in fig. 1, in the optical element 100, when the laminated film 20 is provided on the substrate 10, the fluorine-containing compound layer 22A and the silicon oxide-containing layer 22B are provided so as to form the surface layer of the laminated film 20. That is, the optical element 100 is formed of at least the base 10 and the laminated film 20, and the laminated film 20 has at least the fluorine-containing compound layer 22A and the silicon oxide-containing layer 22B as its outermost surface portion.

The fluorochemical layer 22A has surface irregularities, and the difference in thickness of the irregularities is preferably 10nm or more and 80nm or less. In the exemplary embodiment shown in fig. 1, "maximum thickness of the unevenness" means "T" in the drawing_max"," minimum thickness of unevenness "means" T "in the drawing_min". Thus, in one embodiment, 10nm ≦ T_max-T_min≤80nm。

The fluorochemical layer 22A having surface irregularities preferably has ductility (particularly ductility from the viewpoint of microscopic properties on the order of nanometers to micrometers). Therefore, when a frictional force F is applied to the surface of the fluorochemical layer 22A, the layer surface portion can deform following the frictional force F (see fig. 2 (a)). In the fluorochemical layer 22A, since a force is easily transmitted to a portion having a large layer thickness (i.e., a convex portion) by the friction, the thick portion is preferentially deformed to complement a portion having a small layer thickness (i.e., a concave portion) (see fig. 2 (b)). When a frictional force F' in the opposite direction to the frictional force F is applied to the surface of the fluorochemical layer 22A, the surface returns to the original surface state (i.e., the state of fig. 2 (a)) and deforms (see fig. 2 (c)). Due to such follow-up deformation, the fluorochemical layer 22A can exhibit better abrasion resistance against friction.

In one exemplary embodiment, the surface area of the fluorochemical layer 22A having surface irregularities may be 0.01 μm²Above and 100 μm²Having a maximum thickness T in the following range_maxAnd a minimum thickness T_minThe difference is 10nm to 80nm (see FIG. 3 (a)). In other words, the fluorochemical layer 22A had a surface area of 0.01 μm²Above and 100 μm²Within the following range, layerThe difference between the thickness of the thick portion and the thickness of the thin portion may be 10nm to 80 nm. By applying a voltage of 0.01 μm to the surface area²The surface irregularities are present in the above range, and the surface irregularities can be formed widely. Therefore, the strength of the portion where the surface irregularities are formed can be increased, and the wear resistance can be further improved. In addition, the surface area of the film is 100 μm²The surface irregularities are present in the following range, and the surface irregularities can be formed densely. Therefore, the surface portion of the fluorochemical layer is more likely to be deformed by the frictional force. The fluorochemical layer 22A preferably has a surface area of 0.02 μm²Above and 20 μm²Surface irregularities in the following range, for example, having a surface area of 0.02 μm²Above and 9 μm²Surface irregularities in the following range.

The fluorochemical layer 22A having surface irregularities may have a surface area of 0.01 μm²Above and 100 μm²The following range has a plurality of irregularities (see fig. 3 (b)). In one embodiment, the thickness Ts of the projections adjacent to each other_maxAnd the thickness Ts of the recess_minThe difference is 10nm to 80 nm. In other words, the height difference between the top of the convex portion and the bottom of the concave portion adjacent to each other may be 10nm or more and 80nm or less. With such a configuration, the distance in the in-plane direction between the thick-layer portion and the thin-layer portion of the surface irregularity can be reduced. Therefore, when a frictional force is applied to the surface of the fluorochemical layer 22A, the portion having a large layer thickness can be more easily deformed, and the portion having a small layer thickness can be particularly easily and effectively supplemented. The distance D in the in-plane direction of the adjacent convex and concave portions is preferably 100nm or more and 10 μm or less, for example, 200nm or more and 5 μm or less. This provides excellent abrasion resistance and makes it easier to suppress fogging.

In one embodiment, the fluorochemical layer 22A has a thickness of 3nm or more and 200nm or less. By setting the thickness to 3nm or more, not only the fluorochemical layer 22A can be easily given hydrophobic properties, but also the fluorochemical layer 22A can be easily given good abrasion resistance and weather resistance. In addition, when the thickness is 200nm or less, unexpected surface reflection of light is easily suppressed, and transparency of the optical element is easily maintained more favorably. The thickness of the fluorochemical layer 22A is preferably 4nm or more and 150nm or less, and more preferably 5nm or more and 100nm or less (for example, 10nm or more and 85nm or less, or 15nm or more and 60nm or less).

In the optical element of the present invention, the minimum thickness (minimum thickness to be a layer basis) among the thicknesses of the fluorochemical layer 22A may be about 3nm, 4nm, or 5 nm. Even with such a thin fluorochemical layer, the optical element of the present invention can exhibit desirable weatherability and abrasion resistance. The minimum thickness may be about 15nm, 20nm or 25nm, and thus, as the minimum thickness increases, the effects of weather resistance and abrasion resistance are more easily maintained for a longer period of time. In general, the minimum thickness of the fluorochemical layer provided as the outermost surface portion may be 3nm or more and 25nm or less, 4nm or more and 20nm or less, or 5nm or more and 15nm or less, or the like.

In one embodiment, in the fluorochemical layer having surface irregularities, the occupancy rate of the convex portions of the surface irregularities with respect to the surface area of the entire fluorochemical layer may be 3% or more and 30% or less, for example, 3% or more and 25% or less, or 3% or more and 20% or less. If the occupancy is 3% or more, a portion having a thick layer which can be deformed preferentially by friction can be sufficiently provided, and abrasion of the layer can be more suitably prevented. In addition, if the area ratio is 30% or less, 25% or less, 20% or less, or the like, unexpected surface reflection of light tends to be easily suppressed, and the transparency of the optical element tends to be more favorably maintained.

The "convex portion occupancy of the surface irregularities with respect to the surface area of the entire fluorochemical layer" in the present invention may be a value calculated from an image obtained by observing the surface of the fluorochemical layer using an optical microscope (model MX50, manufactured by OLYMPUS), a reflectance measuring instrument (model USPM-RU, manufactured by OLYMPUS) and/or a microscope (model VHX-5000, manufactured by KEYENCE). For example, the occupancy of the convex portions of the surface irregularities in the fluorochemical layer can be calculated by performing binarization processing on the image obtained by the above-described device. I.e. if in the imageThe surface area of the entire fluorochemical layer is defined as A₁The area of the convex part is defined as A₀The ratio of the convex portion occupancy (%) can be (A)₀/A₁) The convex occupancy was determined by the equation of x 100. More specifically, for example, with respect to an image obtained using a microscope VHX5000 (manufactured by KEYENCE corporation) at an optical magnification of 1000 times, the color tone of the convex portions having convexo-concave surface of the fluorochemical layer was selected using the color extraction function of "VHX image editing software (manufactured by KEYENCE corporation)" to obtain a binary image (see fig. 13). The occupancy (%) can be obtained by calculating the ratio of the area occupied by the spot portion in the binarized image by software.

In the present invention, the surface unevenness can be provided by forming the silicon oxide-containing layer and the fluorine-containing compound layer in this order under pressure conditions that are not continuous with the formation of the optical multi-layer portion. On the other hand, the vapor deposition method can contribute to more effectively forming a fluorine-containing compound layer having surface irregularities by adjusting the amount of fluorine compound to be fed into the vapor deposition apparatus (for example, adjusting the volume of the fluorine compound and/or adjusting the composition of the fluorine compound to be mixed), and/or by changing the amount of fluorine compound to be irradiated (for example, changing the energy for vaporizing the fluorine compound).

In one embodiment, a mixed layer 22C in which a fluorine compound and silicon oxide are mixed is provided between the fluorine compound containing layer 22A and the silicon oxide containing layer 22B (see fig. 4). In other words, the 3 layers form a layer continuously as the outermost surface portion of the laminated film 20. The presence of the mixed layer 22C can further enhance the adhesion between the fluorochemical layer 22A and the silicon oxide-containing layer 22B. Therefore, it is easy to maintain light resistance capable of suppressing deterioration of optical characteristics with respect to light such as ultraviolet light, visible light, and/or infrared light, and abrasion resistance capable of resisting friction caused by external elements for a longer period of time. For example, the thickness of the mixed layer 22C is smaller than the thickness of each of the fluorine-containing compound layer 22A and the silicon oxide-containing layer 22B. That is, as a layer thinner than the fluorine compound containing layer 22A and the silicon oxide containing layer 22B, the mixed layer 22C may be interposed between these layers.

The silicon oxide-containing layer may contain at least silicon oxideContains other compounds and binders such as resin. The silicon oxide-containing layer preferably contains silicon dioxide (SiO) from the viewpoint of high transparency and ease of adjustment of refractive index₂). The thickness of silicon oxide-containing layer 22B may be 100nm or less. When the thickness of the layer is 100nm or less, the layer tends to have a dense and smooth surface property, and the fluorochemical layer 22A tends to be provided with more excellent abrasion resistance, weather resistance and water repellency. The layer thickness of silicon oxide-containing layer 22B is preferably 50nm or less, for example, 30nm or less.

In one embodiment, the hybrid layer 22C has a thickness of 0.5nm or more and 5nm or less. When the thickness is 0.5nm or more, the adhesion between the fluorine-containing compound layer 22A and the silicon oxide-containing layer 22B can be particularly strong. In addition, if the thickness is 5nm or less, unexpected surface reflection of light can be suppressed, and the transparency of the optical element can be easily maintained well. The "thickness of the hybrid layer" in the present invention can be measured by the same method as the maximum thickness and the minimum thickness of the unevenness.

The fluorine compound in the fluorine-containing compound layer of the present invention is not particularly limited, and examples thereof include compounds selected from the group consisting of methyl trifluoroacetate, ethyl perfluoropropionate, ethyl perfluorooctanoate, perfluoroalkyl ether, 2, 2, 2-trifluoroethyl difluoromethyl ether, 1, 2, 2-tetrafluoroethyl ethyl ether, hexafluoroisopropyl methyl ether, 1H-tridecafluoroheptamine, perfluorohexyl iodide, perfluorohexyl ethylene, chlorotrifluoroethylene, fluoroalkyl ether, 3-perfluorohexyl-1, 2-epoxypropane, perfluoropropionic acid, perfluoroheptanoic acid, ethyl 2- (perfluorobutyl) acrylate, perfluoro-4-ethoxybutane, ethyl 2- (perfluorohexyl) acrylate, 1H-heptafluorobutanol, fluoropolyether, 2- (perfluorobutyl) ethanol, perfluorohexane, perfluorocyclobutane, perfluoroethylhexane, perfluoroethylhexylamine, perfluoroethylperfluoroethylperfluoroethylhexane, perfluoroethylhexylamine, perfluoroethylketone, or the like, At least one of perfluorooctane, perfluorodecane, perfluoromethylcyclohexane, perfluoro-1, 3-dimethylcyclohexane, perfluoro-4-methoxybutane, perfluoro-4-ethoxybutane, m-xylene hexafluoride, 6- (perfluorobutyl) hexanol, and 2- (perfluorooctyl) ethanol.

In one embodiment, the fluorine compound comprises a perfluoroalkyl ether group. The number of carbons constituting the perfluoroalkyl ether group may be 1 or more and 10 or less. For example, the perfluoroalkyl ether group may beIs- (C)₄F₈O)_a-(C₃F₆O)_b-(C₂F₄O)_c-(CF₂O)_d-. Wherein a, b, c and d are each independently an integer of 0 to 90, the sum of a, b, c and d may be at least 1, and the order of the repeating units in the formulae shown by a, b, c and d in parentheses is arbitrary. The terminal of the compound including a perfluoroalkyl ether group may be composed of any element or group. When the fluorine compound contains the perfluoroalkyl ether group as described above, the fluorine-containing compound layer can be easily provided with more favorable ductility and more excellent abrasion resistance. Further, more excellent weather resistance (particularly, light resistance) can be easily imparted.

In one embodiment, the fluorine compound in the fluorine compound containing layer comprises a fluorine compound having a group C₃F₆O is a perfluoroalkyl ether group having a linear skeleton of a structural unit. C₃F₆The structural unit of O may be repeated at least 2 times, for example, 5 or more and 10 or less times in the fluorine compound. By the inclusion of fluorine compounds having the formula C₃F₆O is a perfluoroalkyl ether group having a linear skeleton of a structural unit, and a fluorochemical layer having excellent ductility can be easily obtained. C in the perfluoroalkyl ether group₃F₆The skeleton of O may have no branched skeleton but only a linear skeleton.

The perfluoroalkyl ether group in the fluorochemical layer can be confirmed by determining the composition of the constituent material by Nuclear Magnetic Resonance (NMR) spectroscopy (model NMR _ SPECTROMETER, manufactured by Nippon electronics Co., Ltd.) or TOF-SIMS (model TOF-SIMS5, manufactured by ION-TOF).

In one embodiment, the weight average molecular weight of the fluorine compound is 1000 or more and 20000 or less. If the weight average molecular weight is 1000 or more, low friction properties and water repellency can be more effectively imparted to the fluorochemical layer, and if it is 20000 or less, adhesion to other layers in the laminated film can be particularly easily secured. The weight average molecular weight may be 2000 or more and 10000 or less. The weight average molecular weight of the fluorine compound may be a value measured by Gel Permeation Chromatography (GPC) (product model number: HLC8120GPC, manufactured by Tosoh corporation).

In one embodiment, the fluorochemical layer comprises silicon. Since the fluorine-containing compound layer contains silicon, when the fluorine-containing compound layer is adjacent to the silicon oxide-containing layer, the fluorine-containing compound layer can easily exhibit more excellent adhesion to the silicon oxide-containing layer.

In one embodiment, the thickness of the laminated coating film 20 in the optical element is 350nm to 1000nm (see fig. 1). By setting the film thickness to 350nm or more, when the optical element is used in a severe use environment in exterior applications, it is easy to exhibit more excellent abrasion resistance against physical contact (for example, impact of dust and the like) and to impart more excellent durability against corrosion fatigue (for example, acid rain, salt damage and the like). Further, the thickness of the entire optical element can be made thinner by making the film thickness 1000nm or less.

In one embodiment, the optical multi-layer portion of the laminated coating is formed by alternately laminating a high refractive index layer having a relatively high refractive index and a low refractive index layer having a relatively low refractive index. By configuring the optical multilayer portion in this manner, it is easy to prevent light reflection of an unintended wavelength from occurring on the surface of the optical element. Therefore, desired characteristics (for example, transparency, sensor accuracy, and the like) can be easily ensured in an optical element used for an optical lens for a camera, a lens for a photosensor, and the like.

In the exemplary embodiment of the optical element 100 shown in fig. 1, the optical multi-layer portion 23 of the laminated coating film 20 is provided so as to be in contact with the substrate 10 and the silicon oxide-containing layer 22B of the outermost surface portion 22, respectively. That is, the optical element 100 illustrated in fig. 1 is formed of at least the substrate 10 and the laminated coating film 20, and the laminated coating film 20 is composed of an optical multilayer portion 23, and a silicon oxide-containing layer 22B and a fluorine-containing compound layer 22A provided on the optical multilayer portion under a pressure condition discontinuous from the optical multilayer portion.

In the optical multi-layer portion 23, by alternately stacking the high refractive index layers 23H and the low refractive index layers 23L, surface reflection of visible light in a wavelength range of approximately 380nm to 780nm is easily cancelled (see fig. 1). For example, in the optical multi-layer portion 23, the high refractive index layers 23H and the low refractive index layers 23L may be alternately laminated in a range of 4 layers or more and 15 layers or less (more specifically, in a range of 4 layers or more and 10 layers or less, 4 layers or more and 8 layers or less, or 4 layers or more and 7 layers or less). If the number of such layers is 4 or more, desired optical characteristics can be more effectively obtained, and if the number is 15 or less, the entire thickness of the optical element can be made thinner. As an example, the optical multi-layer portion 23 includes 7 layers of the high refractive index layer 23H and the low refractive index layer 23L alternately stacked. Here, the fluorochemical layer 22A and the silicon oxide-containing layer 22B may have a surface antireflection function similarly to the optical multilayer portion 23.

In one embodiment, the optical multilayer portion 23 of the optical element has a film thickness of 350nm or more. When the film thickness is 350nm or more, desired optical characteristics are easily obtained, and further, the film has more excellent rubbing resistance against physical contact and more excellent durability against corrosion fatigue is easily imparted.

The material constituting the high refractive index layer 23H may be at least one selected from oxides of titanium (Ti), zirconium (Zr), hafnium (Hf), tantalum (Ta), and lanthanum (La), and mixtures of these oxides. A Ti/La composite oxide containing titanium and lanthanum can be used in order to obtain a film having high hardness and high smoothness and a film having high environmental test resistance. The refractive index of the high refractive index layer 23H may be 1.80 or more and 2.30 or less from the viewpoint of suppressing surface reflection of light in the visible light wavelength region.

The low refractive index layer 23L may be composed of a binder such as silicon oxide and/or magnesium fluoride, and a resin. From the viewpoint of high transparency and ease of adjustment of refractive index and from the viewpoint of adhesion to the silicon oxide-containing layer, the low refractive index layer 23L may contain silicon dioxide (SiO)₂) The composition may be the same as that of silicon oxide-containing layer 22B. The refractive index of the low refractive index layer 23L may be 1.20 or more and 1.80 or less from the viewpoint of suppressing surface reflection of light in the visible wavelength region.

The material constituting the substrate of the present invention is not particularly limited, and examples thereof include at least one selected from glass frit, resin, metal, and ceramic. In one embodiment, the substrate is made of a glass material, which makes it easy to provide the optical element with high transparency and to improve adhesion to the laminated film.

In the optical element of the present invention, the optical multi-layer portion 23 and the outermost surface portion 22 are preferably provided through mutually discrete steps. In particular, the optical multi-layer portion 23 and the outermost surface portion 22 having the fluorine compound containing layer 22A and the silicon oxide containing layer 22B are preferably formed so that the pressure conditions are not continuous. That is, in the laminated coating film of the present invention, "the outermost surface portion 22 having the silicon oxide-containing layer and the fluorine-containing compound layer" may be provided by temporarily resetting the pressure condition after providing the optical multi-layer portion. Therefore, in the laminated coating, a boundary surface between the optical multilayer portion and the outermost surface portion is easily formed more clearly. For example, in a cross-sectional image of the optical element, an interface between the optical multilayer portion and the outermost surface portion can be seen.

Here, in the formation of the optical multi-layer portion, since a plurality of layers are formed in order, the surface may be undesirably roughened as the number of layers increases. In particular, since crystal grains may be generated in each layer, the surface of the optically multi-layer portion 23 is sometimes formed to be rough (i.e., high in surface roughness). In short, the surface roughness of the rough-surfaced optical multi-layer portion 23 may be Ra >5nm or the like. Therefore, when the outermost surface portion 22 is provided thereon in a discontinuous step, the interface between the optically multi-layer portion 23 and the outermost surface portion 22 is easily expressed as a non-constant, non-linear interface in a cross section (see fig. 5).

In one embodiment, the low refractive index layer 23L as the outermost layer of the optical multi-layer portion 23₄Is of the same composition as silicon oxide-containing layer 22B of outermost surface portion 22. Here, the discontinuous pressure condition is interposed between the low refractive index layer 23L₄And silicon oxide-containing layer 22B. Therefore, in this embodiment, the low refractive index layer 23L as the outermost layer is formed in the optical multi-layer portion 23₄An interface can be seen with silicon oxide-containing layer 22B forming the lowermost layer at outermost surface portion 22. In one embodiment, since the outermost surface layer of the optical multi-layer portion 23 has a rough surface, a non-constant surface portion can be seen in a cross section between the optical multi-layer portion 23 and the outermost surface portion 22,A non-linear interface (or a wavy interface).

When the silicon oxide-containing layer 22B of the outermost surface portion 22 corresponds to an "additional silicon oxide-containing layer", the thickness of the silicon oxide-containing layer 22B is preferably smaller than the outermost surface layer of the optical multi-layer portion 23. For example, the low refractive index layer 23L is formed on the outermost layer of the optical multi-layer portion 23₄In the case of (i.e., the silicon oxide-containing layer of the optical multi-layer portion), the thickness of the silicon oxide-containing layer 22B of the outermost surface portion 22 may be smaller than the thickness of the silicon oxide-containing layer of the optical multi-layer portion 23.

The overall surface shape of the optical element 100 may be planar as shown in fig. 6 (a) and 6 (b), or may be curved as shown in fig. 6 (c) to form a lens. In the optical element 100, the laminated film 20 may be provided only on one side of the surface of the base material 10 (see fig. 6 a), or the laminated film 20 may be provided on both sides of the 2 opposing surfaces (see fig. 6 b).

The optical element 100 may have a shape corresponding to its use. For example, the overall shape of the optical element 100 is a plate-like shape in the case of an optical filter, an infrared transmission window, or the like, and is a concavo-convex shape (a biconcave shape, a biconvex shape, or the like) in the case of a lens for imaging use or the like. The optical element 100 may be formed from a material by any method such as grinding, polishing, and/or press forming.

When the optical element is a lens, the optical element can be formed from a base material obtained by press molding, for example. Hereinafter, a method for forming the base material will be described as an example. First, the raw material is preliminarily formed into a substantially final shape by injection molding. Next, the preformed raw material is housed in a cavity of an optical element molding die heated to a temperature not lower than the load deflection temperature of the raw material but lower than the glass transition temperature. Next, when the temperature of the material substantially matches the optical element molding die and becomes equal to or higher than the deflection temperature under load and lower than the glass transition temperature, the material is pressed while the indenter is lowered, thereby maintaining the deformation. Then, the pressing force is released, the substrate is cooled to the deflection temperature under load, and the material is taken out from the optical element molding die, whereby the substrate of the optical element molded into a desired overall shape (for example, a lens shape) can be obtained.

The optical element 100 of the present invention may be a lens for transmitting at least visible rays. In particular, the lens may be an imaging lens for exterior use. For example, the lens may be a camera lens for a monitoring system for disaster prevention, crime prevention, or the like, and/or a lens used for a camera lens for vehicle mounting.

[ examples ] A method for producing a compound

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[ example 1]

The substrate 10 as a glass lens substrate (refractive index of about 1.825) was ultrasonically cleaned in a weakly alkaline glass cleaning agent, then cleaned with pure water, and then dried at 130 ℃ for 60 minutes (see fig. 1). Next, the temperature of the substrate 10 was set to a set temperature of about 300 ℃, and the low refractive index layer 23L (that is, 23L) was formed by vapor deposition in a state where oxygen gas was introduced₁、23L₂、23L₃And 23L₄) And a high refractive index layer 23H (i.e., 23H)₁、23H₂And 23H₃) The optical multilayer portion 23 is formed on one surface of the substrate 10 by alternately stacking 7 layers. As a material of the high refractive index layer 23H, lanthanum titanate is used. As a material of the low refractive index layer 23L, silicon dioxide is used. The refractive index of each layer was adjusted within the range shown in table 1 so that a desired antireflection function was imparted to the optical element. The vacuum low-pressure condition of the deposition was temporarily cut off, and the ion-assisted deposition apparatus was then used to deposit the optical multi-layer portion 23 (i.e., the low refractive index layer 23L) on the surface thereof₄Upper) a silicon oxide-containing layer 22B and a fluorochemical layer 22A containing a perfluoroalkyl ether group were continuously formed to obtain an optical element 100 (see fig. 1). In the formation of the fluorochemical layer 22A, the amount of the fluorochemical charged into the experimental vapor deposition apparatus was 10 μ L in volume. A mixed layer 22C is formed between the silicon oxide-containing layer 22B and the fluorine-containing compound layer 22A (see fig. 5). In addition, in the cross-sectional image, in the low refractive index layer 23L₄An interface (particularly, a non-constant, non-linear interface in cross section) with silicon oxide-containing layer 22B can be observed. The respective physical property values of each layer are shown in table 1. The refractive index is the refractive index at a wavelength of 500 nm.

[ TABLE 1]

[ example 2]

The substrate 10 as a glass lens substrate (refractive index of about 1.825) was ultrasonically cleaned in a weakly alkaline glass cleaning agent, then cleaned with pure water, and then dried at 130 ℃ for 60 minutes (see fig. 1). Next, the temperature of the substrate 10 was set to a set temperature of about 300 ℃, and the low refractive index layer 23L (that is, 23L) was formed by vapor deposition in a state where oxygen gas was introduced₁、23L₂、23L₃And 23L₄) And a high refractive index layer 23H (i.e., 23H)₁、23H₂And 23H₃) The optical multilayer portion 23 is formed on one surface of the substrate 10 by alternately stacking 7 layers. As a material of the high refractive index layer 23H, lanthanum titanate is used. As a material of the low refractive index layer 23L, silicon dioxide is used. The refractive index of each layer was adjusted within the range shown in table 2 so that a desired antireflection function was imparted to the optical element. The vacuum low-pressure condition of the deposition was temporarily cut off, and the ion-assisted deposition apparatus was then used to deposit the optical multi-layer portion 23 (i.e., the low refractive index layer 23L) on the surface thereof₄Upper) a silicon oxide-containing layer 22B and a fluorochemical layer 22A containing a perfluoroalkyl ether group were continuously formed to obtain an optical element 100 (see fig. 1). In the formation of the fluorochemical layer 22A, the amount of the fluorochemical charged into the experimental vapor deposition apparatus was 3.5. mu.L in volume. A mixed layer 22C is formed between the silicon oxide-containing layer 22B and the fluorine-containing compound layer 22A (see fig. 5). In addition, in the cross-sectional image, in the low refractive index layer 23L₄A non-constant, non-linear interface is formed with silicon oxide-containing layer 22B. The respective physical property values of the respective layers are shown in table 2. The refractive index is the refractive index at a wavelength of 500 nm.

[ TABLE 2]

Comparative example 1

A base material as a glass lens substrate (refractive index of about 1.825) was ultrasonically cleaned in a weakly alkaline glass cleaner, then cleaned with pure water, and then dried at 130 ℃ for 60 minutes. Then, the temperature of the substrate was set to a set temperature of about 300 ℃, and the low refractive index layer (that is, 23L) was formed by vapor deposition in a state where oxygen gas was introduced₁’、23L₂’、23L₃' and 23L₄') and a high refractive index layer (i.e., 23H)₁’、23H₂' and 23H₃') 7 layers were alternately stacked to form an optical multilayer portion on one surface of the substrate. As a material of the high refractive index layer, lanthanum titanate was used. As a material of the low refractive index layer, silicon dioxide is used. The refractive index of each layer was adjusted within the range shown in table 3 so that a desired antireflection function was imparted to the optical element. Then, using the same experimental vapor deposition apparatus, the fluorochemical layer 22' containing a perfluoroalkyl ether group was formed without heating setting, and an optical element was obtained. The amount of the fluorine compound charged into the experimental vapor deposition apparatus was 10. mu.L in volume. The respective physical property values of each layer are shown in table 3. The refractive index is the refractive index at a wavelength of 500 nm.

[ TABLE 3 ]

(comparison of example 1 with comparative example 1)

The following experimental tests of "abrasion resistance test" and "weather resistance test" were carried out for example 1 and comparative example 1.

(abrasion resistance test)

The optical element was evaluated by a method in accordance with JIS standard (JIS K5600-5-10) using Steel Wool (SW)And (3) wear resistance. Specifically, steel wool #0000 (manufactured by BONSTAR) was placed on the surface of the laminated film of the optical element, and applied at 1kg/cm²Under the load of (3), the test piece was reciprocated to perform a scratch test. The reciprocating movement was carried out 3000 times at a moving speed of 80mm/sec and a moving distance of. + -. 10 mm.

(weather resistance test)

The resistance to deterioration caused by natural environment in the optical element was evaluated by a method in accordance with JIS standard (JIS B7754). Specifically, the surface of the laminated coating of the optical element was irradiated with an ultraviolet fluorescent lamp at an illuminance: 30W/m²Irradiation (irradiation wavelength 313nm) and black plate temperature 63 ℃ for 4 hours and dark black wetting for 4 hours were alternately repeated for a total of 500 hours. Due to such tests, the durability of the optical element was evaluated particularly from the viewpoint of light resistance.

The results are shown in fig. 7 and 8 (see the item of "contact angle" described later for the evaluation parameters on the ordinate of the graph). As is clear from the graphs of fig. 7 and 8, it was confirmed that the optical element including the fluorochemical layer and the silicon oxide-containing layer formed under the pressure condition discontinuous from the optical multilayer portion can exhibit more excellent weather resistance and abrasion resistance.

(comparison of example 1 with example 2)

In example 2, the same experimental tests as the "abrasion resistance test" and the "weather resistance test" were also performed. The difference between example 1 and example 2 is that the thickness of the fluorochemical layer provided as the outermost surface portion is different. Specifically, the minimum thickness of the fluorine-containing compound layer in example 2 was about 5nm, whereas the minimum thickness of the fluorine-containing compound layer in example 1 was about 15 nm.

The results are shown in fig. 9 and 10. As is clear from the graphs of fig. 9 and 10, it was confirmed that, in the optical element including the fluorochemical layer and the silicon oxide-containing layer formed under the pressure condition discontinuous from the optical multilayer portion, weather resistance and abrasion resistance were maintained even when the fluorochemical layer was made thinner. In addition, in an optical element having a fluorine-containing compound layer provided thicker, a tendency to maintain weather resistance and abrasion resistance for a longer period of time has also been confirmed.

[ Cross-sectional analysis of the fluorine-containing Compound layer by TEM ]

The fluorine-containing compound layer was analyzed in cross section by a Transmission Electron Microscope (TEM). First, the cross-sectional direction cross section of the optical element in example 1 was cut out at an acceleration voltage of 10 to 40KV by a focused ion beam apparatus (model FB2200, manufactured by hitachi). Next, a Transmission Electron Microscope (TEM) (model JEM-2800 manufactured by JEOL) was used to obtain a cross-sectional TEM image of the periphery of the fluorochemical layer 22A at a magnification of 500000 times at an acceleration voltage of 200KV (see fig. 11). From the obtained images, the maximum thickness (T) of the irregularities of the fluorochemical layer 22A was obtained_max) And minimum thickness (T)_min). Maximum thickness (T) of unevenness of the fluorochemical layer in FIG. 11_max) And minimum thickness (T)_min) 30.1nm and 5.1nm, respectively, T_max-T_minIs 25.0 nm. This measurement confirmed that the difference in the thickness of the irregularities of the fluorochemical layer 22A was in the range of 10nm to 80 nm. In addition, it was confirmed by the measurement that the thick portion was 10nm to 80nm thick as compared with the thin portion in the fluorochemical layer 22A.

Similarly, a Transmission Electron Microscope (TEM) was used to obtain a cross-sectional TEM image of the periphery of the fluorochemical layer 22A with a magnification of 1000000 (see fig. 12). As shown in fig. 12, it was confirmed that the hybrid layer 22C had a thickness of 0.5nm or more and 5nm or less in example 1 (see table 1). In addition, in the cross-sectional TEM image, it was also confirmed that the low refractive index layer 23L was included in the low refractive index layer 23L₄An interface (particularly, a nonlinear interface) is formed with silicon oxide-containing layer 22B.

[ surface analysis of fluorochemical layer by optical microscope ]

The surface of the fluorochemical layer was analyzed by an optical microscope. The fluorine-containing compounds of examples 1 and 2 and comparative example 1 were obtained at 1000-fold magnification by using a reflectance measuring instrument (model USPM-RU manufactured by OLYMPUS) and a microscope (model VHX-5000 manufactured by KEYENCE)The surface image of the layer is subjected to binarization processing on the obtained image (fig. 13 shows a binarized image of example 1 as a representative example). In the binarized image, the occupancy of the convex portions of the surface irregularities in the fluorochemical layer was calculated. Specifically, the area a of the convex portion (the region where the light point in the shading in fig. 13) of the binarized image is obtained₀(example 1: 12207 μm²Example 2: 2410 μm²Comparative example 1: 20519 μm²) Surface area A of the entire fluorochemical layer 22A₁(74347μm²) Ratio (%) of (c).

The convex portion occupancy rate of the surface irregularities in the fluorochemical layer 22A is as follows.

Example 1: 16.4 percent

Example 2: 3.2 percent of

Comparative example 1: 27.6 percent

When the results of the "abrasion resistance test" and the "weather resistance test" are considered together, it can be confirmed that the optical element of the present invention in which the convex portion occupancy of the surface irregularities of the fluorine-containing compound layer is 3% or more and 20% or less has a high possibility of exhibiting both excellent weather resistance and abrasion resistance.

[ structural analysis of fluorine-containing Compound layer by TOF-SIMS ]

The spectral intensity ratio of the ION derived from the fluoroalkyl ether component on the surface of the fluorochemical layer 22A in example 1 to the entire polymer was measured by TOF-SIMS (model TOF-SIMS5 manufactured by ION-TOF). From the obtained spectral intensity ratio and cycle, it was confirmed that C is present in the fluorine-containing compound layer₃F₆O is a perfluoroalkyl ether group having a linear skeleton of a structural unit.

As a reliability test, the following test was performed on the optical element of example 1 in addition to the above-described "abrasion resistance test" and "weather resistance test".

[ details of reliability test ]

(brine cycle test)

The resistance to corrosion resistance by brine was evaluated by a method in accordance with JIS standard (JIS H8502). Specifically, 8-hour spraying and 16-hour wet storage were repeated for 9 cycles using a 5% saline solution and saline spray tester (STP 200, manufactured by Suga).

(Damp-Heat test)

The resistance to deterioration by moist heat was evaluated by a method in accordance with JIS standard (JIS C60068). Specifically, the optical element was left at (i)110 ℃, (ii)85 ℃/85%, (iii) -40 ℃ for 1000 hours.

(thermal shock test)

The resistance to deterioration caused by repeated environments at high and low temperatures was evaluated by a method in accordance with JIS standards (JIS 60068-2-14 (Na)). Specifically, the atmospheric temperature of the optical element was cycled 1000 times or more between 110 ℃ and-40 ℃. The holding time under each temperature condition in 1 cycle was set to 0.5 hour.

(chemical resistance/oil resistance test)

The test results were evaluated for resistance to various chemicals and oils and fats used in automobiles. Specifically, the optical element was immersed in gasoline, engine oil (manufactured by ENEOS), an automobile detergent (manufactured by CPC), an alkaline cleaning solution (manufactured by Karcher), and an aqueous NaOH solution for a predetermined time.

[ evaluation of reliability test ]

(contact Angle)

The contact angle with water was measured, and the optical element was evaluated after each reliability test. Specifically, a droplet of approximately 1 μ L was formed on the surface of the laminated coating film of each optical element after the test, and the contact angle with water was measured. Here, the "contact angle with water" refers to an angle formed by a tangent line to the water surface and the solid surface at a point where the solid is in contact with water. The larger the value of the contact angle with water, the more effectively the fluorochemical layer in the laminated coating remains. In the measurement of the contact angle with water, the contact angle with water was measured at 5 points on the surface of the laminated coating film, and the case where all the contact angles with water were 100 ° or more in 5 points was designated as "o", and the case where even 1 point among 9 points had a portion having a contact angle with water of less than 100 ° was designated as "x". The results are shown in the table. When the base material had a lens shape, only 1 point at the apex was measured.

As shown in table 4, all of the samples after the above tests showed good contact angles. Therefore, it is found that the optical element of the present invention is less likely to lose the hydrophobicity of the fluorochemical layer even under severe environments. That is, it is found that the fluorine-containing compound layer can effectively remain in a severe environment.

(amount of change in spectral reflectance)

The visible light reflectance was measured, and the optical element was evaluated after each reliability test. Specifically, the spectral reflectance in the wavelength range of 400nm to 700nm was measured with the light incidence angle of 0 degrees on the surface of the laminated film of the optical element before and after each test, and the average wavelength value in this range was calculated. Here, the same portion was measured on the surface of the laminated film of the optical element before and after the above test. For the measurement of the spectral reflectance, a reflectance measuring instrument (model USPM-RU, manufactured by OLYMPUS) was used. From the obtained measurement values, the change rate of the average spectral reflectance of the optical element after the test with respect to the average spectral reflectance of the optical element before the test was calculated. The results are shown in Table 4.

As shown in table 4, all of the samples after the above tests showed small changes in spectral reflectance. Therefore, it is found that the antireflection function of the laminated film is less likely to be impaired even in a severe environment in the optical element of the present invention. That is, it was found that the laminated film can be effectively left in a severe environment.

[ TABLE 4 ]

The embodiments have been described above, but only a typical example is illustrated. Therefore, the optical element and the method of manufacturing the same of the present invention are not limited thereto, and those skilled in the art will readily understand that various aspects can be considered.

For example, in the above, the optical multi-layer portion and the outermost surface portion of the laminated coating film are mainly formed by the vapor phase method, but the present invention is not limited thereto. For example, the optical multi-layer portion and/or the outermost surface portion of the laminated coating film may be formed by at least 1 wet coating method selected from spin coating, flow coating, dipping, spray coating, and inkjet.

Industrial applicability

The present invention can be applied to the field of optical elements requiring high visible transmittance. In short, the optical element of the present invention is merely illustrative, and can be used for various optical units such as an imaging unit (for example, a camera lens for a monitoring system for disaster prevention, crime prevention, and the like, a camera lens for a vehicle-mounted camera, and the like), an optical element mirror simple unit, an optical pickup unit, and the like, various optical systems such as a high-quality imaging optical system, an objective optical system, a scanning optical system, and a pickup optical system, and the like, an imaging apparatus, an optical pickup apparatus, an optical scanning apparatus, and the like.

Description of the reference numerals

10: base material

20: laminated coating film

22: the outermost surface part

22A: fluorine-containing compound layer

22B: layer containing silicon oxide

22C: hybrid layer

23: optical multilayer part

23H: high refractive index layer

23L: low refractive index layer

100: optical element