WO2024203501A1

WO2024203501A1 - Optical element, lens unit, and camera module

Info

Publication number: WO2024203501A1
Application number: PCT/JP2024/010433
Authority: WO
Inventors: 建杉本; 貴則加本; 昌之西川; 小百合中川; ティジェニファートレスダマスコ; 明典山本; 政孝川上
Original assignee: ニデック株式会社; ニデックインスツルメンツ株式会社
Priority date: 2023-03-31
Filing date: 2024-03-18
Publication date: 2024-10-03
Also published as: JP2024146496A

Abstract

This optical element has an optical axis Lx. The optical element comprises a plastic lens, a hard coat layer, and an anti-reflection film. The hard coat layer is positioned between the plastic lens and the anti-reflection film. The anti-reflection film is disposed on at least one surface side of the plastic lens. The thickness of the hard coat layer on the optical axis is 2-20 μm. The minimum thickness of the hard coat layer is 2 μm or more, and the maximum thickness of the hard coat layer is 20 μm or less.

Description

Optical element, lens unit and camera module

The present invention relates to an optical element, a lens unit, and a camera module.

In order to protect the light-transmitting plastic lens substrate, it is known to coat the plastic lens substrate with a hard coat layer that is harder than the plastic lens substrate, and to provide an anti-reflection layer on the surface of the hard coat layer to prevent light reflection (see, for example, Patent Document 1).

Patent Document 1 describes the use of a plastic lens having an antireflection layer on a hard coat layer covering a plastic lens substrate as a spectacle lens. In the plastic lens of Patent Document 1, the antireflection layer is a multilayer film in which a low refractive index film made of silicon dioxide ( _SiO2 ) and a high refractive index film made of trisilicon _tetranitride ( _Si3N4 ) are alternately laminated, and the low refractive index film and the high refractive index film of the antireflection layer are set to specific film thicknesses to improve the durability of the plastic lens.

Japanese Patent Publication: JP 2008-76598 A

However, even with the plastic lens of Patent Document 1, there is a risk that the durability of the optical element will decrease due to the anti-reflection layer peeling off or the hard coat layer being damaged due to the surrounding environment. On the other hand, in a plastic lens, if the hard coat layer becomes thicker, the decrease in durability can be suppressed, but there is a risk that optical distortion will occur and the optical properties will decrease.

The present invention was made in consideration of the above problems, and its purpose is to provide an optical element, lens unit, and camera module that can improve durability and suppress deterioration of optical characteristics.

An exemplary optical element of the present invention is an optical element having an optical axis, and includes a plastic lens, an anti-reflection film disposed on at least one surface side of the plastic lens, and a hard coat layer located between the plastic lens and the anti-reflection film. The thickness of the hard coat layer on the optical axis is 2 μm or more and 20 μm or less.

An exemplary lens unit of the present invention includes a plurality of lenses and a housing member that houses the plurality of lenses. The plurality of lenses are arranged in order from the opening of the housing member, and the outermost lens of the plurality of lenses that is located on the opening side of the housing member is the optical element described above.

An exemplary camera module of the present invention includes the lens unit described above and an image sensor.

The exemplary present invention can provide an optical element, lens unit, and camera module that can improve durability and suppress deterioration of optical characteristics.

FIG. 1A is a schematic diagram of an example of an optical element according to this embodiment. FIG. 1B is an enlarged view of a portion of FIG. 1A. FIG. 2A is a schematic diagram of a camera module according to the present embodiment. FIG. 2B is an enlarged view of a portion of FIG. 2A. FIG. 3A is a schematic diagram of a camera module according to the present embodiment. FIG. 3B is an enlarged view of a portion of FIG. 3A. FIG. 4A is an exploded view of the camera module according to the present embodiment. FIG. 4B is a schematic diagram of a manufacturing process of the camera module according to this embodiment. FIG. 4C is a schematic diagram showing the camera module according to the present embodiment.

The optical element, lens unit, and camera module according to the embodiments of the present invention will be described below with reference to the drawings as appropriate. Note that in the drawings, the same or corresponding parts are given the same reference symbols and the description will not be repeated. The dimensions, shapes, and dimensional relationships between components in the drawings are not necessarily the same as the actual dimensions, shapes, and dimensional relationships between components. In particular, the thicknesses of the anti-reflection film, hard coat layer, and plastic lens in the drawings may differ significantly from the actual thicknesses of the anti-reflection film, hard coat layer, and plastic lens. Note that in this specification, the "thickness" of each part of the optical element refers to the length parallel to the optical axis direction of the optical element.

Below, the optical element 10 according to this embodiment will be described with reference to Figs. 1A and 1B. Fig. 1A is a schematic diagram of the optical element 10 according to this embodiment. Fig. 1B is a partially enlarged view of Fig. 1A.

As shown in Figures 1A and 1B, the optical element 10 has a curved shape. Typically, the optical element 10 has a spherical shape. The optical element 10 has a spherical shape centered on a central axis.

The optical element 10 has an optical axis Lx. The optical axis Lx passes through the center of the curved shape of the optical element 10. The optical element 10 has a symmetric structure centered on the optical axis Lx. Typically, the optical element 10 has a rotationally symmetric structure centered on the optical axis Lx. Light is incident on the optical element 10 from a direction along the optical axis Lx.

The optical element 10 comprises a plastic lens 11, a hard coat layer 12, and an anti-reflection film 13. The plastic lens 11, the hard coat layer 12, and the anti-reflection film 13 are laminated in this order. Typically, the plastic lens 11, the hard coat layer 12, and the anti-reflection film 13 are arranged in close contact with each other in this order.

[Plastic Lens 11]
The plastic lens 11 transmits light. For example, the plastic lens 11 is transparent. The plastic lens 11 may also be translucent or have light-transmitting properties.

Typically, the plastic lens 11 is made of resin. The plastic lens 11 may be composed of a single member. For example, the plastic lens 11 includes a resin having a cyclic imide structure as a ring structure. Examples of such resins include AZP manufactured by Asahi Kasei Corporation, and RM-104, RM-250, and RM-100-Z manufactured by Nippon Shokubai Co., Ltd.

The plastic lens 11 has a curved shape. Typically, the plastic lens 11 has a spherical shape. At least one surface of the plastic lens 11 may be a convex or concave surface. When the plastic lens 11 has a convex or concave surface, the plastic lens 11 functions as a lens (specifically, for example, a biconvex lens, a plano-convex lens, a convex meniscus lens, and a concave meniscus lens).

The plastic lens 11 may have a convex surface. For example, the radius of curvature of the plastic lens 11 is 9 mm or more and 16 mm or less.

The thermal expansion coefficient of the plastic lens 11 is preferably 60 ppm/K or more and 150 ppm/K or less. This makes it possible to suppress the effects of thermal stress between the plastic lens 11 and the anti-reflection coating 13.

[Hard coat layer 12]
The hard coat layer 12 covers the plastic lens 11. For example, the hard coat layer 12 covers one surface of the plastic lens 11 located on the object side in the extension direction of the optical axis Lx. The hard coat layer 12 has a higher hardness than the plastic lens 11. The hard coat layer 12 imparts scratch resistance to the plastic lens 11 and improves adhesion between the plastic lens 11 and the antireflection film 13.

The hard coat layer 12 transmits light. For example, the hard coat layer 12 is transparent. The hard coat layer 12 may also be semi-transparent or have light-transmitting properties.

The hard coat layer 12 may have a base layer. Typically, the base layer includes an organic material layer or an organosilicon compound layer. In addition, in the hard coat layer 12, metal oxide fine particles may be dispersed in the base layer.

The elastic modulus of the hard coat layer 12 is preferably 5 GPa or more and 12 GPa or less. When the elastic modulus of the hard coat layer 12 is 5 GPa or more, damage to the plastic lens 11 can be suppressed. Furthermore, when the elastic modulus of the hard coat layer 12 is 12 GPa or less, the occurrence of cracks in the hard coat layer 12 due to temperature changes can be suppressed.

Typically, the hard coat layer 12 can be formed by drying the component liquid attached to the surface of the plastic lens 11, and then curing the film of the component liquid with electromagnetic waves such as ultraviolet rays or an electron beam. The component liquid may be heated when drying.

In one example, the hard coat layer 12 may be formed by a spin coating method. In this case, the component liquid of the hard coat layer 12 is discharged onto the plastic lens 11 rotating at a predetermined rotation speed, and the component liquid of the hard coat layer 12 is cured by applying electromagnetic waves such as ultraviolet rays or an electron beam to the component liquid.

Alternatively, the hard coat layer 12 may be formed by a dipping method. In this case, the plastic lens 11 is immersed in the component liquid of the hard coat layer 12, and then the component liquid of the hard coat layer 12 on the plastic lens 11 rotating at a predetermined rotation speed is cured by applying electromagnetic waves such as ultraviolet rays or an electron beam.

When the hard coat layer 12 is formed on the surface of the plastic lens 11 while rotating the plastic lens 11, the thickness of the hard coat layer 12 varies depending on the distance from the optical axis Lx. Typically, the thickness of the hard coat layer 12 decreases as the distance from the optical axis Lx increases.

[Anti-reflection film 13]
The anti-reflection film 13 covers the hard coat layer 12. For example, the anti-reflection film 13 covers the air side of the hard coat layer 12. The anti-reflection film 13 suppresses reflection of light incident on the anti-reflection film 13. The anti-reflection film 13 suppresses at least a part of light traveling in a direction incident on the plastic lens 11 from being reflected on the surface side of the plastic lens 11. For example, the anti-reflection film 13 suppresses visible light traveling in a direction incident on the plastic lens 11 from being reflected on the surface side of the plastic lens 11.

The anti-reflective film 13 transmits light. For example, the anti-reflective film 13 is transparent. The anti-reflective film 13 may also be semi-transparent or have light-transmitting properties.

The thickness of the anti-reflection film 13 is 100 nm or more and 1000 nm or less. The thickness of the anti-reflection film 13 may be 200 nm or more and 900 nm or less, or may be 300 nm or more and 800 nm or less.

The thermal expansion coefficient of the anti-reflection coating 13 is preferably 1 ppm/K or more and 10 ppm/K or less. This makes it possible to suppress the effects of thermal stress between the plastic lens 11 and the anti-reflection coating 13.

The anti-reflection film 13 may have a laminated film structure. For example, layers with different compositions are laminated in the anti-reflection film 13.

For example, the anti-reflection film 13 is made of an inorganic oxide. Examples of inorganic oxides in the anti-reflection film 13 include metal oxides such as silicon oxide, titanium oxide, lanthanum titanate, tantalum oxide, and niobium oxide. For example, layers of multiple types of metal oxides are stacked in the anti-reflection film 13.

For example, the anti-reflection film 13 has a high refractive index film and a low refractive index film. The anti-reflection film 13 is configured so that the high refractive index film and the low refractive index film are alternately overlapped.

The refractive index of a high refractive index film is higher than that of a low refractive index film. Typically, in the visible range, the refractive index of a high refractive index film is higher than that of a low refractive index film.

The high refractive index film contains trisilicon tetranitride ( _Si3N4 ). The low refractive index film contains silicon dioxide ( _SiO2 ). In this way, the high refractive index film contains trisilicon _tetranitride ( _Si3N4 ) and the low refractive index film contains silicon dioxide ( _SiO2 ) _, thereby improving thermal shock resistance.

For example, the high refractive index film is 1.9 or more. In one example, the high refractive index film is 1.9 or more and 2.3 or less.

For example, the refractive index of the low refractive index film is 1.5 or more and 1.8 or less. In one example, the refractive index of the low refractive index film is 1.6 or more and 1.75 or less.

The thickness of the high refractive index film and the low refractive index film is 5 nm or more and 200 nm or less. This allows the high refractive index film and the low refractive index film to be formed uniformly, and allows multiple high refractive index films and low refractive index films to be arranged in the anti-reflection film 13. The thickness of the high refractive index film and the low refractive index film may be 10 nm or more and 180 nm or less, or may be 20 nm or more and 170 nm or less.

The anti-reflection film 13 preferably transmits light in the visible range while reflecting light in the ultraviolet range. In the anti-reflection film 13, it is preferable that the average reflectance of visible light wavelengths is lower than the average reflectance of ultraviolet wavelengths.

In addition, from the viewpoint of further suppressing the effect of thermal stress between the plastic lens 11 and the anti-reflection coating 13, it is preferable that the difference between the thermal expansion coefficient of the plastic lens 11 and the thermal expansion coefficient of the anti-reflection coating 13 is relatively small. For example, it is preferable that the thermal expansion coefficient of the plastic lens 11 is 60 ppm/K or more and 100 ppm/K or less, and the thermal expansion coefficient of the anti-reflection coating 13 is 5 ppm/K or more and 10 ppm/K or less.

As shown in FIG. 1B, the plastic lens 11 has a curved shape. Here, one surface of the plastic lens 11 is curved, and the other surface is flat. The thickness of the plastic lens 11 varies depending on the distance from the optical axis Lx.

The thickness of the hard coat layer 12 varies depending on the distance from the optical axis Lx. Typically, the thickness of the hard coat layer 12 is greatest at the center of the optical axis Lx. Also, typically, the thickness of the hard coat layer 12 is smallest at the outer edge.

Typically, the thickness Lx2 of the outer edge of the hard coat layer 12 is smaller than the thickness Lx1 of the hard coat layer 12 at the optical axis Lx. However, it is preferable that the difference between the thickness Lx1 of the hard coat layer 12 at the optical axis Lx and the thickness Lx1 of the outer edge of the hard coat layer 12 is relatively small. For example, the difference between the thickness Lx1 of the hard coat layer 12 at the optical axis Lx and the thickness Lx2 of the outer edge of the hard coat layer 12 is preferably 15 μm or less, and more preferably 6 μm or less.

If the thickness of the hard coat layer on the optical axis Lx is small, when the optical element is exposed to an outdoor environment and the adhesion at the interface between the hard coat layer and the anti-reflection film decreases, the anti-reflection film may peel off from the hard coat layer or the hard coat layer may be damaged, resulting in a decrease in the durability of the optical element.

On the other hand, if the thickness of the hard coat layer on the optical axis Lx is large, optical distortion occurs in the optical element, and the optical characteristics of the optical element may deteriorate. Furthermore, if the thickness of the hard coat layer on the optical axis Lx becomes even larger, the film condition of the hard coat layer becomes non-uniform, and cracks may occur in the hard coat layer.

In the optical element 10 of this embodiment, the thickness Lx1 of the hard coat layer 12 on the optical axis Lx is 2 μm or more, so that even if the optical element 10 is exposed to an outdoor environment, the anti-reflection film 13 can be prevented from peeling off from the hard coat layer 12 or the hard coat layer 12 can be prevented from being damaged and the durability of the optical element 10 can be prevented from decreasing on the optical axis Lx through which a high amount of light transmits. In addition, in the optical element 10 of this embodiment, the thickness Lx1 of the hard coat layer 12 on the optical axis Lx is 20 μm or less, so that the optical characteristics of the optical element 10 can be prevented from decreasing on the optical axis Lx through which a high amount of light transmits.

In the optical element 10 of this embodiment, the thickness Lx1 of the hard coat layer 12 on the optical axis Lx is 2 μm or more and 20 μm or less. Since the thickness Lx1 of the hard coat layer 12 on the optical axis Lx is 2 μm or more, peeling of the anti-reflection film 13 from the hard coat layer 12 can be suppressed even when light is irradiated onto the optical element 10 on the optical axis Lx through which a high amount of light of the optical element 10 transmits. Furthermore, since the thickness of the hard coat layer 12 on the optical axis Lx is 20 μm or less, optical distortion can be suppressed and cracks can be suppressed from occurring in the hard coat layer 12.

The minimum thickness of the hard coat layer 12 is preferably 2 μm or more. This makes it possible to prevent the durability of the entire optical element 10 from decreasing.

The maximum thickness of the hard coat layer 12 is preferably 20 μm or less. This makes it possible to prevent the optical properties of the entire optical element 10 from deteriorating.

The optical element 10 of this embodiment has relatively little optical distortion and exhibits relatively high durability. For this reason, the optical element 10 is suitable for use in surveillance cameras or vehicle-mounted cameras. Even when the surveillance camera or vehicle-mounted camera is used in an outdoor environment for a long period of time, the optical element 10 can be used continuously.

In this embodiment, the optical element 10 has an optical axis Lx. The optical element 10 includes a plastic lens 11, a hard coat layer 12, and an anti-reflection film 13. The hard coat layer 12 is located between the plastic lens 11 and the anti-reflection film 13. The anti-reflection film 13 is disposed on at least one surface side of the plastic lens 11. The thickness Lx1 of the hard coat layer 12 on the optical axis Lx is 2 μm or more and 20 μm or less.

By making the thickness Lx1 of the hard coat layer 12 on the optical axis Lx 2 μm or more, peeling of the anti-reflection film 13 from the hard coat layer 12 can be suppressed even when ultraviolet light is irradiated on the optical element 10 on the optical axis Lx of the optical element 10. In addition, by making the thickness Lx1 of the hard coat layer 12 on the optical axis Lx 20 μm or less, optical distortion can be suppressed and cracks can be suppressed from occurring in the hard coat layer 12.

Generally, when an optical element is exposed to ultraviolet light in an outdoor environment, degradation occurs on the surface of the hard coat layer, and adhesion at the interface between the hard coat layer and the anti-reflection film can decrease. In contrast, by making the thickness Lx1 of the hard coat layer 12 on the optical axis Lx 2 μm or more, peeling of the anti-reflection film 13 from the hard coat layer 12 and loss of the hard coat layer 12 can be suppressed even when the optical element 10 is irradiated with light. This makes it possible to provide an optical element 10 that has excellent weather resistance and suppresses deterioration of optical properties.

The minimum thickness of the hard coat layer 12 is 2 μm or more, and the maximum thickness of the hard coat layer 12 is 20 μm or less. By making the minimum thickness of the hard coat layer 12 2 μm or more, peeling of the anti-reflection film 13 can be suppressed even when light is irradiated onto the optical element 10. Furthermore, by making the maximum thickness of the hard coat layer 12 20 μm or less, the occurrence of optical distortion can be suppressed, and the occurrence of cracks in the hard coat layer 12 can be suppressed.

The elastic modulus of the hard coat layer 12 is 5 GPa or more and 12 GPa or less. When the elastic modulus of the hard coat layer 12 is 5 GPa or more, damage to the plastic lens 11 can be suppressed. Furthermore, when the elastic modulus of the hard coat layer 12 is 12 GPa or less, cracks caused by thermal stress can be suppressed from occurring in the hard coat layer 12.

The thermal expansion coefficient of the plastic lens 11 is 60 ppm/K or more and 150 ppm/K or less. By having the thermal expansion coefficient of the plastic lens 11 be 60 ppm/K or more and 150 ppm/K or less, the effect of thermal stress between the plastic lens 11 and the anti-reflection coating 13 can be reduced.

The thermal expansion coefficient of the anti-reflection film 13 is 1 ppm/K or more and 10 ppm/K or less. By having the thermal expansion coefficient of the anti-reflection film 13 be 1 ppm/K or more and 10 ppm/K or less, the effect of thermal stress between the plastic lens 11 and the anti-reflection film 13 can be reduced.

The thermal expansion coefficient of the plastic lens 11 is 60 ppm/K or more and 100 ppm/K or less, and the thermal expansion coefficient of the anti-reflective coating 13 is 5 ppm/K or more and 10 ppm/K or less. By having the thermal expansion coefficient of the plastic lens 11 be 60 ppm/K or more and 100 ppm/K or less, and the thermal expansion coefficient of the anti-reflective coating 13 be 5 ppm/K or more and 10 ppm/K or less, the effect of thermal stress between the plastic lens 11 and the anti-reflective coating 13 can be further reduced.

The difference between the thickness Lx1 of the hard coat layer 12 at the optical axis Lx and the thickness Lx2 of the outer edge is 15 μm or less. By making the difference between the thickness Lx1 of the hard coat layer 12 at the optical axis Lx and the thickness Lx2 of the outer edge 15 μm or less, a relatively thin hard coat layer 12 can be suitably formed on the surface of the plastic lens 11 while rotating the component liquid of the hard coat layer 12 at a predetermined speed.

In the optical element 10 shown in Figures 1A and 1B, the hard coat layer 12 and the anti-reflection film 13 are disposed on one side of the plastic lens 11, but this embodiment is not limited to this. The hard coat layer 12 and the anti-reflection film 13 may be disposed on both sides of the plastic lens 11.

Next, the camera module 200 according to this embodiment will be described with reference to Figures 1A, 1B, 2A, and 2B. Figure 2A is a schematic diagram showing an example of the camera module 200 according to this embodiment, and Figure 2B is an enlarged portion of Figure 2A. The camera module 200 captures an image of the surroundings.

As shown in FIG. 2A, the camera module 200 includes a lens unit 100 and an image sensor 210. The image sensor 210 receives light that passes through the lens unit 100 and captures an image of the surroundings.

The lens unit 100 includes a plurality of lenses 110. At least one of the plurality of lenses 110 is an optical element 10.

The lenses 110 include a first lens 110a, a second lens 110b, a third lens 110c, a fourth lens 110d, and a fifth lens 110e. The first lens 110a, the second lens 110b, the third lens 110c, the fourth lens 110d, and the fifth lens 110e are arranged in order from the object side to the image side.

For example, the first lens 110a is the optical element 10 described above. That is, the first lens 110a includes the plastic lens 11 described above, the hard coat layer 12, and the anti-reflection film 13.

The lens unit 100 further includes a housing member 120, a fixing member 122, a filter 130, and a sealing member 140. The housing member 120 is tubular. Typically, the housing member 120 is cylindrical. Note that the inner peripheral surface of the housing member 120 may be provided with irregularities.

The housing member 120 houses a plurality of lenses 110 and filters 130. The housing member 120 is formed from a material that does not transmit light. For example, the housing member 120 is formed from a material that does not transmit visible light and ultraviolet light.

The fixing member 122 fixes at least one of the lenses 110 to the housing member 120. The fixing member 122 penetrates the housing member 120 in a direction perpendicular to the optical axis Lx and fixes at least one of the lenses to the housing member 120.

The first lens 110a, the second lens 110b, the third lens 110c, the fourth lens 110d, and the fifth lens 110e are placed in the housing member 120. At least one of the first lens 110a, the second lens 110b, the third lens 110c, the fourth lens 110d, and the fifth lens 110e may be arranged so that at least a portion of the lens is exposed from the housing member 120. For example, the first lens 110a is arranged so that at least a portion of the lens is exposed from the housing member 120, and the other second lens 110b, the third lens 110c, the fourth lens 110d, and the fifth lens 110e are arranged within the housing member 120.

Here, the diameter of the first lens 110a is larger than the diameters of the second lens 110b, the third lens 110c, the fourth lens 110d, and the fifth lens 110e. Also, the diameter of the fifth lens 110e is larger than the diameters of the second lens 110b, the third lens 110c, and the fourth lens 110d.

The fixing member 122 fixes the first lens 110a to the housing member 120. The fixing member 122 presses the edge surface of the first lens 110a to fix the first lens 110a to the housing member 120.

The filter 130 is disk-shaped. The filter 130 selectively transmits incident light. For example, the filter 130 selectively transmits light of a specific wavelength from the incident light. Here, the filter 130 is disposed in the housing member 120. For example, as shown in FIG. 2A, the image sensor 210 is disposed outside the lens unit 100.

The filter 130 is disposed on the image side relative to the fifth lens 110e. The filter 130 allows the wavelength of light reaching the image sensor 210 to be selected. The image sensor 210 is a photoelectric conversion element that converts irradiated light into an electrical signal. The image sensor 210 is, for example, a CMOS image sensor or a CCD image sensor. However, the image sensor 210 is not limited to these. The image sensor 210 captures an image of a subject formed by the multiple lenses 110. Note that the image sensor 210 may be disposed on the image side relative to the filter 130 (lens unit 100).

The first lens 110a is a negative meniscus lens with a convex surface facing the object side. In this embodiment, the convex object side surface of the first lens 110a is spherical, and the concave image side surface is aspheric.

The second lens 110b, the third lens 110c, the fourth lens 110d and the fifth lens 110e may be made of resin (plastic lenses) or glass.

The second lens 110b, the third lens 110c, the fourth lens 110d and the fifth lens 110e may be a biconvex lens, a plano-convex lens, a convex meniscus lens or a concave meniscus lens.

As described above, the lens unit 100 includes multiple lenses 110, and at least one of the multiple lenses 110 is an optical element 10, thereby suppressing deterioration of the lenses 110 in the lens unit 100.

In addition, the first lens 110a, which includes the above-mentioned plastic lens 11, hard coat layer 12, and anti-reflection film 13, is arranged exposed from the housing member 120, and the remaining lenses (second lens 110b, third lens 110c, fourth lens 110d, and fifth lens 110e) are arranged inside the housing member 120, thereby suppressing deterioration of lenses other than the highly durable first lens 110a.

The sealing member 140 deforms between the first lens 110a and the housing member 120 to seal the gap between the first lens 110a and the housing member 120. For example, the sealing member 140 is a ring-shaped elastic body. In one example, the sealing member 140 is an O-ring.

The lens unit 100 is suitable for use as an on-board lens for capturing images of the surroundings of a vehicle. For example, the lens unit 100 is used as an on-board lens for capturing images of the rear or sides of a vehicle.

Because the lens unit 100 includes the sealing member 140, even if water is splashed onto the lens unit 100 from the outside, the water can be prevented from entering the inside of the lens unit 100 (i.e., the inside of the housing member 120).

The first lens 110a is provided with the above-mentioned plastic lens 11, hard coat layer 12, and anti-reflection film 13, so that ultraviolet rays entering the housing member 120 can be effectively suppressed. This makes it possible to suppress deterioration of the lens in the housing member 120.

For example, the diameter Ld of the first lens 110a may be 1 mm or more and 100 mm or less, or 2 mm or more and 50 mm or less. In one example, the diameter Ld of the first lens 110a is 13.70 mm or more and 13.75 mm or less.

According to this embodiment, the lens unit 100 includes a plurality of lenses 110 and a housing member 120 that houses the plurality of lenses 110. The plurality of lenses 110 are arranged in order from the opening of the housing member 120. The outermost lens of the plurality of lenses 110 that is located on the opening side of the housing member 120 is the optical element 10 described above. This can improve the weather resistance of the lens unit 100.

The camera module 200 includes the lens unit 100 described above and an image sensor 210. This improves the weather resistance of the camera module 200.

Next, the camera module 200 according to this embodiment will be described with reference to Figures 1 to 3B. Figure 3A is a schematic diagram showing an example of the camera module 200 according to this embodiment, and Figure 3B is an enlarged portion of Figure 3A. The camera module 200 in Figures 3A and 3B has a similar configuration to the camera module 200 described above with reference to Figures 2A and 2B, except that it further includes a light-shielding member 150 instead of the fixing member 122, and therefore duplicated descriptions will be omitted to avoid redundancy.

As shown in FIG. 3A, the camera module 200 includes a lens unit 100 and an image sensor 210. The lens unit 100 includes a plurality of lenses 110. At least one of the plurality of lenses 110 is an optical element 10.

The lens unit 100 further includes a housing member 120, a filter 130, a sealing member 140, and a light blocking member 150. The housing member 120 is tubular. Typically, the housing member 120 is cylindrical. Note that the inner peripheral surface of the housing member 120 may be provided with irregularities.

The housing member 120 houses a plurality of lenses 110 and filters 130. The housing member 120 is formed from a material that does not transmit light. The housing member 120 is formed from a material that does not transmit visible light and ultraviolet light.

The light blocking member 150 blocks the first lens 110a. The light blocking member 150 blocks the periphery of the first lens 110a. The light blocking member 150 extends in a direction perpendicular to the optical axis Lx relative to the housing member 120. The light blocking member 150 extends along the periphery of the first lens 110a. The light blocking member 150 prevents the first lens 110a from detaching from the housing member 120. The light blocking member 150 may be a single member together with the housing member 120.

The light blocking member 150 covers the periphery of the first lens 110a with a length that is 0.5% to 10% of the diameter of the first lens 110a. Therefore, the effective diameter Ed of the first lens 110a is smaller than the diameter Ld of the first lens 110a.

For example, the diameter Ld of the first lens 110a may be 1 mm or more and 100 mm or less, or 2 mm or more and 50 mm or less. The length Sd of the light blocking member 150 along a direction perpendicular to the optical axis Lx may be 0.005 mm or more and 10 mm or less, or 0.01 mm or more and 5 mm or less.

For example, the diameter Ld of the first lens 110a is 13.70 mm or more and 13.75 mm or less. In one example, the light blocking member 150 covers the periphery of the first lens 110a over a length of 0.1 mm or more and 1.0 mm or less from the outer edge of the first lens 110a. Therefore, the length Sd of the light blocking member 150 along a direction perpendicular to the optical axis Lx is 0.1 mm or more and 1.0 mm or less. Therefore, the effective diameter Ed of the first lens 110a is 11.70 mm or more and 13.55 mm or less.

In this embodiment, the lens unit 100 includes a light-shielding member 150, which prevents the first lens 110a from detaching from the housing member 120.

Next, the camera module 200 according to this embodiment will be described with reference to Figures 1 to 4C. Figure 4A is an exploded view of the camera module 200 according to this embodiment. Figure 4B is a schematic diagram of the manufacturing process of the camera module 200 according to this embodiment. Figure 4C is a schematic diagram showing the camera module 200 according to this embodiment.

As shown in FIG. 4A, the housing member 120 can house a plurality of lenses 110. At least one of the plurality of lenses 110 is an optical element 10.

The storage member 120 has a tubular shape. Typically, the storage member 120 has a cylindrical shape.

The lenses 110 include a first lens 110a, a second lens 110b, a third lens 110c, a fourth lens 110d, and a fifth lens 110e. The storage member 120 has storage portions capable of storing the first lens 110a, the second lens 110b, the third lens 110c, the fourth lens 110d, and the fifth lens 110e, respectively.

Note that here, a protrusion 150a is provided on the outer edge of one side of the housing member 120. Typically, the protrusion 150a is formed from the same material as the housing member 120. The protrusion 150a is a single member with the housing member 120. The protrusion 150a extends from the housing member 120 parallel to the optical axis Lx.

As shown in FIG. 4B, the multiple lenses 110, the filter 130, and the sealing member 140 are housed in the housing member 120. Here, the first lens 110a, the second lens 110b, the third lens 110c, and the sealing member 140 are inserted into the housing member 120 from one side to the other. The fourth lens 110d, the fifth lens 110e, and the filter 130 are inserted into the housing member 120 from the other side to one side. The filter 130 is located between the multiple lenses 110 and the image sensor 210.

As shown in FIG. 4C, the light shielding member 150 is formed by bending the protrusion 150a relative to the housing member 120 in a direction perpendicular to the optical axis Lx. The protrusion 150a is pressed in a heated state, so that it is bent relative to the housing member 120 in a direction perpendicular to the optical axis Lx. The light shielding member 150 shields the first lens 110a, which is the outermost lens. The light shielding member 150 prevents light entering the lens unit 100 from entering the outer edge of the first lens 110a. The light shielding member 150 also prevents the first lens 110a from detaching from the housing member 120.

According to this embodiment, the lens unit 100 further includes a light-shielding member 150 that shields the outer edge of the outermost lens, in addition to the multiple lenses 110, the housing member 120, the filter 130, and the sealing member 140. As a result, even if the outer edge of the hard coat layer 12 of the outermost lens is thin, the light-shielding member 150 can block light, thereby preventing a decrease in adhesion at the interface between the anti-reflection film 13 and the hard coat layer 12, and preventing deterioration of the hard coat layer 12.

The light-shielding member 150 is a single member together with the housing member 120. This makes it possible to prevent an increase in the number of parts due to the light-shielding member 150, which shields the outer edge of the hard coat layer 12 from light.

The following describes examples of the present invention. However, the present invention is not limited to the scope of the following examples.

[Example 1]
First, the optical element 10 of Example 1 was fabricated.

A plastic lens 11 was prepared using RM-104 manufactured by Nippon Shokubai Co., Ltd. The plastic lens 11 was a meniscus lens with the convex surface facing the object side, and the outer diameter of the plastic lens 11 was approximately 14 mm.

The surface of the plastic lens 11 was coated with a hard coat layer 12. The hard coat layer 12 was a photocurable resin material made of urethane or the like. The hard coat layer 12 was formed by applying a component liquid of the hard coat layer 12 to the plastic lens 11 by spin coating, heating and drying the film of the component liquid, and then curing the film with electromagnetic waves such as ultraviolet rays or an electron beam.

The surface of the hard coat layer 12 was coated with an antireflection film 13. The antireflection film 13 was formed by alternately forming _a high refractive index film made of _Si3N4 and a low refractive index film made of _SiO2 by a sputtering method. In this manner, the optical element 10 of Example 1 was produced.

The thickness of the hard coat layer 12 was measured in the optical element 10 of Example 1. The thickness Lx1 of the hard coat layer 12 on the optical axis Lx was 5.4 μm, while the thickness Lx2 of the outer edge of the hard coat layer 12 was 2.1 μm.

Next, the optical property test and weather resistance test were performed on the optical element 10 of Example 1 under the following conditions.

[Optical property test]
The optical element 10 of Example 1 was irradiated with fluorescent light from a fluorescent light source and visually inspected for optical distortion.

[Weather resistance test]
A weathering test was carried out using a highly accelerated weathering tester, a 7.5 kW super xenon weather meter. In the weathering test, 500 cycles were repeated, with an irradiance of 180 W/ ^m2 , consisting of 18 minutes of irradiation and rainfall, followed by 102 minutes of irradiation alone. During and after the weathering test, it was checked whether the anti-reflection film 13 had peeled off and whether the hard coat layer 12 had been damaged.

Table 1 shows the thickness of the hard coat layer 12 at the optical axis in the optical element 10 of Example 1, the thickness of the outer edge of the hard coat layer 12, and the results of the optical property test and weather resistance test of the optical element 10. In this specification, in visual inspection under a fluorescent light source, those that show no optical distortion are indicated with an "O" and those that show optical distortion are indicated with an "X". Also in this specification, those that show no peeling of the anti-reflective film or damage to the hard coat layer in visual inspection after the weather resistance test are indicated with an "O", and those that show either peeling of the anti-reflective film or damage to the hard coat layer are indicated with an "X".

As shown in Table 1, in the optical element 10 of Example 1, no distortion occurred in the light transmitted through the optical element 10. Furthermore, in the optical element 10 of Example 1, peeling of the anti-reflection film 13 and damage to the hard coat layer 12 were not observed even after the weather resistance test.

The optical elements 10 of Examples 2 to 3 were fabricated in the same manner as the optical element 10 of Example 1, and the optical elements 10 of Examples 2 to 3 were subjected to optical property tests and weather resistance tests in the same manner as the optical element 10 of Example 1. In addition, the optical elements of Comparative Examples 1 to 3 were fabricated, and the optical property tests and weather resistance tests were also performed in the same manner as the optical element 10 of Example 1. Table 1 shows the thickness of the hard coat layer at the optical axis, the thickness of the outer edge of the hard coat layer, and the results of the optical property tests and weather resistance tests for the optical elements of Examples 1 to 3 and Comparative Examples 1 to 3.

In the optical element 10 of Example 2, the thickness of the hard coat layer 12 on the optical axis and the thickness of the outer edge were 8.6 μm and 2.7 μm, respectively, and no distortion occurred in the light transmitted through the optical element 10. Furthermore, even after the weather resistance test, no peeling of the anti-reflection film 13 or damage to the hard coat layer 12 was confirmed.

In the optical element 10 of Example 3, the thickness of the hard coat layer 12 at the optical axis and the thickness of the outer edge were 15.8 μm and 5.2 μm, respectively, and no distortion occurred in the light transmitted through the optical element 10. Furthermore, even after the weather resistance test, no peeling of the anti-reflection film 13 or damage to the hard coat layer 12 was confirmed.

In the optical element of Comparative Example 1, the thickness of the hard coat layer on the optical axis and the thickness of the outer edge were 1.4 μm and 0.3 μm, respectively, and no distortion occurred in the light transmitted through the optical element of Comparative Example 1. However, after the weather resistance test, either peeling of the anti-reflection film or damage to the hard coat layer occurred.

In the optical element of Comparative Example 2, the thickness of the hard coat layer on the optical axis and the thickness of the outer edge were 23.5 μm and 8.3 μm, respectively, and distortion occurred in the light transmitted through the optical element of Comparative Example 2. On the other hand, even after the weather resistance test, no peeling of the anti-reflection film or damage to the hard coat layer was confirmed.

In the optical element of Comparative Example 3, the thickness of the hard coat layer on the optical axis and the thickness of the outer edge were 33.9 μm and 10.2 μm, respectively, and distortion occurred in the light transmitted through the optical element of Comparative Example 3. Furthermore, after the weather resistance test, either peeling of the anti-reflection film or damage to the hard coat layer occurred.

In the optical elements 10 of Examples 1 to 3, there was no optical distortion, and no peeling of the anti-reflection film 13 or damage to the hard coat layer 12 occurred. On the other hand, in the optical element of Comparative Example 1, there was no optical distortion, but either peeling of the anti-reflection film or damage to the hard coat layer occurred. In the optical element of Comparative Example 2, there was no peeling of the anti-reflection film or damage to the hard coat layer, but there was optical distortion. In the optical element of Comparative Example 3, there was optical distortion, and either peeling of the anti-reflection film or damage to the hard coat layer occurred.

The present technology may have the following configuration.
(1) An optical element having an optical axis,
Plastic lenses and
An anti-reflection film disposed on at least one surface side of the plastic lens;
a hard coat layer located between the plastic lens and the anti-reflection film,
The optical element, wherein the hard coat layer has a thickness of 2 μm or more and 20 μm or less on the optical axis.

(2) The optical element according to (1), wherein the hard coat layer has a minimum thickness of 2 μm or more and a maximum thickness of 20 μm or less.

(3) The optical element described in (1) or (2), in which the elastic modulus of the hard coat layer is 5 GPa or more and 12 GPa or less.

(4) An optical element described in any one of (1) to (3), in which the thermal expansion coefficient of the plastic lens is 60 ppm/K or more and 150 ppm/K or less.

(5) An optical element described in any one of (1) to (4), in which the thermal expansion coefficient of the antireflection film is 1 ppm/K or more and 10 ppm/K or less.

(6) The thermal expansion coefficient of the plastic lens is 60 ppm/K or more and 100 ppm/K or less,
The optical element according to any one of (1) to (5), wherein the antireflection film has a thermal expansion coefficient of 5 ppm/K or more and 10 ppm/K or less.

(7) An optical element described in any one of (1) to (6), in which the difference between the thickness of the hard coat layer at the optical axis and the thickness of the outer edge is 15 μm or less.

(8) a plurality of lenses;
a housing member that houses the plurality of lenses,
The plurality of lenses are arranged in order from the opening of the housing member,
A lens unit, wherein an outermost lens of the plurality of lenses that is located on the opening side of the housing member is an optical element described in any one of (1) to (7).

(9) The lens unit described in (8) further includes a light-shielding member that shields the outer edge of the outermost lens.

(10) The lens unit described in (9), in which the light blocking member is a single member together with the housing member.

(11) A lens unit according to any one of (8) to (10),
The camera module includes an imaging element.

10 Optical element 11 Plastic lens 12 Hard coat layer 13 Anti-reflection film

Claims

An optical element having an optical axis,
Plastic lenses and
An anti-reflection film disposed on at least one surface side of the plastic lens;
a hard coat layer located between the plastic lens and the anti-reflection film,
The optical element, wherein the hard coat layer has a thickness of 2 μm or more and 20 μm or less on the optical axis.
The optical element according to claim 1 , wherein the hard coat layer has a minimum thickness of 2 μm or more and a maximum thickness of 20 μm or less.
The optical element according to claim 1 or 2, wherein the elastic modulus of the hard coat layer is 5 GPa or more and 12 GPa or less.
The optical element according to claim 1 or 2, wherein the thermal expansion coefficient of the plastic lens is 60 ppm/K or more and 150 ppm/K or less.
The optical element according to claim 1 or 2, wherein the thermal expansion coefficient of the anti-reflection film is 1 ppm/K or more and 10 ppm/K or less.
The thermal expansion coefficient of the plastic lens is 60 ppm/K or more and 100 ppm/K or less,
3. The optical element according to claim 1, wherein the anti-reflection film has a thermal expansion coefficient of 5 ppm/K or more and 10 ppm/K or less.
The optical element according to claim 1 or 2, wherein the difference between the thickness of the hard coat layer at the optical axis and the thickness of the outer edge is 15 μm or less.
Multiple lenses and
a housing member that houses the plurality of lenses,
The plurality of lenses are arranged in order from the opening of the housing member,
A lens unit, wherein an outermost lens of the plurality of lenses that is positioned on an opening side of the housing member is the optical element according to claim 1 .
The lens unit of claim 8, further comprising a light-shielding member that shields the outer edge of the outermost lens.
The lens unit according to claim 9, wherein the light blocking member is a single member together with the housing member.
A lens unit according to claim 8;
The camera module includes an imaging element.