JP2023163128A - Optical member and lens unit - Google Patents

Abstract

To provide an optical member capable of improving durability.SOLUTION: An optical member 100 comprises: a translucent member 110; a hard coat layer 120 that covers the translucent member 110; and an antireflection layer 130 that covers the hard coat layer 120. The antireflection layer 130 is configured that a high refractive index film 130a and low refractive index film 130b are alternately superimposed. The high refractive index film 130a includes Si3 N4. The low refractive index film 130b includes SiO2. The total number of films of the high refractive index film 130a and the low refractive index film 130b is an even number. A ratio of the thickness of a thick film to the thickness of a thin film out of adjacent two films is 6 times or lower with respect to each of the high refractive index film 130a and the low refractive index film 130b on the antireflection layer 130. The average reflectance of the antireflection layer 130 in a wavelength region 300 to 400 nm is 40% or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical member and a lens unit.

In order to protect a light-transmitting member that transmits light, it is known to cover the light-transmitting member with a hard coat film that is harder than the light-transmitting member. In this case, if the translucent member and hard coat film are exposed to ultraviolet rays, cracks may occur in the hard coat film, so coating the hard coat film with an antireflection film is being considered (for example, patented (See Reference 1).

Patent Document 1 discloses that a low refractive index layer made of a metal oxide with a relatively low refractive index and a high refractive index layer made of a metal oxide with a relatively high refractive index are provided on a hard coat film that covers a resin substrate. An optical member is described that includes an antireflection film formed by laminating 11 to 15 layers of . The optical member of Patent Document 1 exhibits a high reflectance when ultraviolet light is incident at a relatively small angle of incidence, and a low luminous reflectance when ultraviolet light is incident at a relatively large angle of incidence. Prevents cracks from occurring in the hard coat film.

Japanese Patent Application Publication No. 2013-205805

However, in the optical member of Patent Document 1, the antireflection film may peel off when the surrounding environment changes. For example, when the optical member of Patent Document 1 is left outdoors for a long time, the antireflection film may peel off due to temperature changes or climate changes.

The present invention has been made in view of the above problems, and an object thereof is to provide an optical member and a lens unit that can improve durability.

An exemplary optical member of the present invention includes a light-transmitting member, a hard coat layer covering the light-transmitting member, and an antireflection layer covering the hard coat layer. The antireflection layer is configured such that high refractive index films and low refractive index films are alternately overlapped. The high refractive index film includes Si ₃ N ₄ . The low refractive index film includes SiO ₂ . The total number of the high refractive index films and the low refractive index films is an even number. For each of the high refractive index film and the low refractive index film in the antireflection layer, the ratio of the thickness of the thicker film to the thickness of the thinner film of two adjacent films is 6 times or less. The average reflectance of the antireflection layer in the wavelength range of 300 to 400 nm is 40% or more.

An exemplary lens unit of the present invention includes a plurality of lenses, and at least one lens of the plurality of lenses is the optical member described above.

The exemplary present invention can provide an optical member and a lens unit that can improve durability.

FIG. 1 is a schematic diagram of an example of an optical member according to this embodiment. FIG. 2 is a table showing the film structure of the antireflection layer in the optical member according to this embodiment. FIG. 3 is a schematic diagram of an example of a lens unit according to this embodiment.

Hereinafter, optical members according to embodiments of the present invention will be described with reference to the drawings as appropriate. In the drawings, the same or corresponding parts are given the same reference numerals and the description will not be repeated. The dimensions, shapes, and magnitude relationships between components in the drawings are not necessarily the same as the actual dimensions, shapes, and magnitude relationships between components. In particular, the thicknesses of the antireflection layer, hard coat layer, and translucent member in the drawings may be significantly different from the actual thicknesses of the antireflection layer, hard coat layer, and translucent member. Note that in this specification, the "thickness" of each part of the optical member indicates the length of the optical member in the optical axis direction.

The optical member 100 according to this embodiment will be described below with reference to FIG. FIG. 1 is a schematic diagram of an optical member 100 according to this embodiment.

The optical member 100 includes a translucent member 110, a hard coat layer 120, and an antireflection layer 130. Transparent member 110, hard coat layer 120, and antireflection layer 130 are laminated in this order. Typically, the transparent member 110, the hard coat layer 120, and the antireflection layer 130 are arranged in this order in close contact with each other.

[Transparent member 110]
The translucent member 110 transmits light. The translucent member 110 has translucency. Translucent member 110 may be transparent or translucent. Typically, the translucent member 110 is made of resin. Translucent member 110 may be composed of a single member. For example, the transparent member 110 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 Corporation.

Translucent member 110 has a flat surface. Note that at least one surface of the transparent member 110 may be a convex surface or a concave surface. When the light-transmitting member 110 has a convex surface or a concave surface, the light-transmitting member 110 functions as a lens (specifically, for example, a biconvex lens, a plano-convex lens, a convex meniscus lens, and a concave meniscus lens).

[Hard coat layer 120]
The hard coat layer 120 covers the transparent member 110. The hard coat layer 120 covers the air side of the transparent member 110. Hard coat layer 120 has higher hardness than translucent member 110. The hard coat layer 120 provides scratch resistance to the light-transmitting member 110 and improves the adhesion between the light-transmitting member 110 and the antireflection layer 130 .

It is preferable that the hard coat layer 120 transmits light. For example, the hard coat layer 120 has translucency. Hard coat layer 120 may be transparent or translucent.

In this embodiment, the hard coat layer 120 includes a base layer. Typically, the base layer includes an organic material layer or an organosilicon compound layer. Further, in the hard coat layer 120, metal oxide fine particles may be dispersed in the base layer.

[Anti-reflection layer 130]
Antireflection layer 130 coats hard coat layer 120 . The antireflection layer 130 covers the air side of the hard coat layer 120. The antireflection layer 130 suppresses reflection of light. The antireflection layer 130 suppresses at least a portion of the light that is about to enter the light-transmitting member 110 from being reflected on the surface. For example, it is preferable that the antireflection layer 130 suppresses visible light that is about to enter the transparent member 110 from being reflected on the surface.

The thickness of the antireflection layer 130 is 100 nm or more and 1000 nm or less. The thickness of the antireflection layer 130 may be 200 nm or more and 900 nm or less, or 300 nm or more and 800 nm or less.

The antireflection layer 130 includes a high refractive index film 130a and a low refractive index film 130b. The antireflection layer 130 is configured such that high refractive index films 130a and low refractive index films 130b are alternately overlapped. The antireflection layer 130 has a laminated film structure.

The refractive index of the high refractive index film 130a is higher than the refractive index of the low refractive index film 130b. Typically, in the visible range, the refractive index of the high refractive index film 130a is higher than the refractive index of the low refractive index film 130b.

The high refractive index film 130a contains trisilicon tetranitride (Si ₃ N ₄ ). The low refractive index film 130b contains silicon dioxide (SiO ₂ ). In this way, the high refractive index film 130a contains trisilicon tetranitride (Si ₃ N ₄ ) and the low refractive index film 130b contains silicon dioxide (SiO ₂ ), thereby improving thermal shock resistance.

For example, the high refractive index film 130a has a refractive index of 1.9 or more. In one example, the high refractive index film 130a has a refractive index of 1.9 or more and 2.3 or less.

For example, the refractive index of the low refractive index film 130b is 1.5 or more and 1.8 or less. In one example, the refractive index of the low refractive index film 130b is 1.6 or more and 1.75 or less.

The thickness of the high refractive index film 130a and the low refractive index film 130b is 5 nm or more and 200 nm or less. Thereby, the high refractive index film 130a and the low refractive index film 130b can be formed uniformly, and a plurality of high refractive index films 130a and low refractive index films 130b can be arranged in the antireflection layer 130. The thickness of the high refractive index film 130a and the low refractive index film 130b may be 10 nm or more and 180 nm or less, or 20 nm or more and 170 nm or less.

The antireflection layer 130 has a laminated film structure. In the antireflection layer 130, the number of high refractive index films 130a is the same as the number of low refractive index films 130b, and the total number of high refractive index films 130a and low refractive index films 130b in the antireflection layer 130 is the same as the number of low refractive index films 130b. is an even number. Typically, trisilicon tetranitride (Si ₃ N ₄ ) exhibits compressive stress and silicon dioxide (SiO ₂ ) exhibits tensile stress. In this way, the high refractive index film 130a and the low refractive index film 130b exhibit different stresses. Since the number of high refractive index films 130a is the same as the number of low refractive index films 130b, stress balance can be maintained in the antireflection layer 130, and durability can be improved.

The total number of high refractive index films 130a and low refractive index films 130b is preferably 10 or less. The high refractive index film 130a and the low refractive index film 130b may be formed by sputtering. By forming by sputtering, the thicknesses of the high refractive index film 130a and the low refractive index film 130b can be controlled more precisely. Since the total number of films of the high refractive index film 130a and the low refractive index film 130b is 10 or less, even when the high refractive index film 130a and the low refractive index film 130b are formed by sputtering at high temperatures, the antireflection layer The time for forming the transparent member 130 can be shortened, and the load on the transparent member 110 can be reduced.

Note that even if films containing Si ₃ N ₄ are formed continuously with interruptions when forming the antireflection layer 130, one high refractive index film 130a is formed. The same applies to the low refractive index film 130b.

As described above, the total number of high refractive index films 130a and low refractive index films 130b is preferably 10 or less. Thereby, the stress in the antireflection layer 130 can be easily adjusted. For example, the total number of high refractive index films 130a and low refractive index films 130b may be 6 or more and 8 or less. Thereby, the antireflection layer 130 with appropriate hardness can be easily formed.

In this specification, the order of the films of the antireflection layer 130 may be described in the order closest to the hard coat layer 120. For example, the film closest to the hard coat layer 120 among the stacked films of the antireflection layer 130 is described as the first film, and the film closest to the hard coat layer 120 after the first film among the stacked films of the antireflection layer 130 is described as the first film. It is described as a second film.

In the antireflection layer 130, the high refractive index films 130a and the low refractive index films 130b are arranged alternately. It is preferable that the difference in film thickness between the adjacent high refractive index film 130a and low refractive index film 130b in the antireflection layer 130 is relatively small. For example, as understood from FIG. 2, the thickness of one of the adjacent high refractive index film 130a and low refractive index film 130b in the antireflection layer 130 is greater than the thickness of the other thinner film. It is preferably 6 times or less. In this specification, the ratio of the thickness of the thicker film to the thickness of the thinner film among two adjacent high refractive index films 130a and low refractive index films 130b is referred to as "film thickness ratio". There is. When the film thickness ratio is 6 times or less, the hardness of the antireflection layer 130 can be improved.

In one example, in the antireflection layer 130, the second film is sandwiched between the first film and the third film. In this case, among the thicknesses of the first film and the second film, it is preferable that the thickness of the thicker film is 6 times or less the thickness of the thinner film. For example, when the thickness of the first film is greater than the thickness of the second film, the thickness of the first film is preferably six times or less than the thickness of the second film. Alternatively, when the thickness of the second film is greater than the thickness of the first film, the thickness of the second film is preferably six times or less than the thickness of the first film.

Similarly, regarding the thicknesses of the second film and the third film, it is preferable that the thickness of the thicker film is 6 times or less the thickness of the thinner film. For example, when the thickness of the second film is greater than the thickness of the third film, the thickness of the second film is preferably six times or less than the thickness of the third film. Alternatively, when the thickness of the third film is greater than the thickness of the second film, the thickness of the third film is preferably six times or less than the thickness of the second film.

As described above, in the antireflection layer 130, the total number of high refractive index films 130a and low refractive index films 130b is an even number. Therefore, the first film of the antireflection layer 130 that is closest to the hard coat layer 120 is different from the film that is farthest from the hard coat layer 120 (the outermost film). For example, when the first film is the high refractive index film 130a, the outermost film is the low refractive index film 130b. Conversely, when the first film is the low refractive index film 130b, the outermost film is the high refractive index film 130a.

In the anti-reflection layer 130, by adjusting the film thickness of the high refractive index film 130a and the film thickness of the low refractive index film 130b, the anti-reflection layer 130 has an average reflection in the wavelength range (300-400 nm) corresponding to the ultraviolet region. The reflectance can be made 40% or more, and the average reflectance in the wavelength range (450-800 nm) corresponding to the visible region can be made 2.0% or less. This can suppress ultraviolet light from entering the hard coat layer 120 and the transparent member 110 via the antireflection layer 130, and improve the adhesion between the antireflection layer 130, the hard coat layer 120, and the transparent member 110. The decline can be suppressed. Furthermore, visible light can be transmitted through the hard coat layer 120 and the transparent member 110 via the antireflection layer 130.

The outermost film of the antireflection layer 130 is preferably a low refractive index film 130b containing SiO ₂ . Thereby, the reflectance in the visible range can be easily reduced. In this case, since the total number of films in the antireflection layer 130 is an even number, the film adjacent to the hard coat layer 120 in the antireflection layer 130 becomes the high refractive index film 130a.

Further, according to the optical member 100 of the present embodiment, the average reflectance at wavelengths corresponding to the ultraviolet region (e.g. 300-400 nm) is 40% or more, and at wavelengths corresponding to the visible region (e.g. 450-800 nm). The average reflectance can be reduced to 2.0% or less. Therefore, it is possible to suppress ultraviolet light from entering the optical member 100. Thereby, deterioration of the optical member 100 due to ultraviolet rays can be suppressed, so that the durability of the optical member 100 can be improved. Such an optical member 100 is suitably used, for example, as a lens for a lens unit of a vehicle-mounted camera for monitoring the surroundings of a vehicle.

The optical member 100 of this embodiment includes a light-transmitting member 110, a hard coat layer 120 covering the light-transmitting member 110, and an antireflection layer 130 covering the hard coat layer 120. The antireflection layer 130 is configured such that high refractive index films 130a and low refractive index films 130b are alternately overlapped. The high refractive index film 130a contains Si ₃ N ₄ and the low refractive index film 130b contains SiO ₂ . The total number of high refractive index films 130a and low refractive index films 130b is an even number. For each of the high refractive index film 130a and the low refractive index film 130b in the antireflection layer 130, the ratio of the thickness of the thicker film to the thickness of the thinner film of the two adjacent films is 6 times or less. The average reflectance of the antireflection layer 130 in the wavelength range of 300 to 400 nm is 40% or more. Thereby, the durability of the optical member 100 can be improved.

Further, the total number of high refractive index films 130a and low refractive index films 130b is preferably 10 or less. Thereby, the stress in the antireflection layer 130 can be easily adjusted.

The total number of high refractive index films 130a and low refractive index films 130b is preferably 6 or more and 8 or less. Thereby, the hardness of the antireflection layer 130 can be adjusted appropriately.

The film located farthest from the hard coat layer 120 in the antireflection layer 130 is preferably the low refractive index film 130b. Thereby, the reflectance of the antireflection layer 130 can be easily reduced in the visible range.

Note that the antireflection layer 130 preferably reflects light in the ultraviolet range while transmitting light in the visible range. Note that the reflectance of the antireflection layer 130 may be obtained by actual measurement or by calculation.

The reflectance of the antireflection layer 130 can be obtained by calculation. For example, Essential Mcleod software, which models optical coatings using transfer matrix methods, can be used to predict the propagation of electromagnetic waves through thin film stacks. Optical interference matrices are an effective method for calculating the reflectance of film stacks. Considering an optical thin film system with N films under the condition where the incident angle of light is zero degrees, n _j is the refractive index, k _j is the extinction coefficient, d _j is the thickness of each film, and n ₀ is the refractive index of air. (n ₀ =1). The reflectance of a film stack can be calculated by the optical admittance (Y), which is the ratio of the total tangential magnetic field (C) and electric field (B). Depending on the refractive index and thickness of each film, the interference matrix of each film can be determined using the characteristic matrix shown in the following equation (1).

where δ _r =2πNd cos θ/λ is the effective optical thickness of the film at a particular wavelength and _nm is the refractive index of the substrate. If q is the membrane next to the substrate, the order is:

M ₁ indicates the matrix associated with the first membrane. The same applies to _M2 , etc. As in the case of a single surface, n ₀ does not need to be a real number for reflectance and only for transmittance to have a valid meaning. Using equations (1) and (2), the reflectance (R) can be derived as shown in equation (3).

As described above, the antireflection layer 130 preferably transmits light in the visible range and reflects light in the ultraviolet range. The antireflection layer 130 preferably has an average reflectance of 2.0% or less in the wavelength range of 450 to 800 nm, and an average reflectance of 40% or more in the wavelength range of 300 to 400 nm.

The optical member 100 of this embodiment exhibits relatively high durability. Therefore, the optical member 100 is suitably used in a surveillance camera or a vehicle-mounted camera. Even when a surveillance camera or a vehicle-mounted camera is used for a long time in an outdoor environment, the optical member 100 can be used continuously.

Note that in the optical member 100 shown in FIG. 1, the hard coat layer 120 and the antireflection layer 130 are disposed on one side of the transparent member 110, but the present embodiment is not limited thereto. A hard coat layer 120 and an antireflection layer 130 may be disposed on both sides of the transparent member 110.

Next, the lens unit 200 according to this embodiment will be explained with reference to FIGS. 1 to 3. FIG. 3 is a schematic diagram of an example of the lens unit 200 according to this embodiment.

The lens unit 200 includes a plurality of lenses, and at least one lens of the plurality of lenses is the optical member 100.

Lens unit 200 includes a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, and a fifth lens 250. The first lens 210, the second lens 220, the third lens 230, the fourth lens 240, and the fifth lens 250 are arranged in order from the object side toward the image side.

For example, the first lens 210 is the optical member 100 described above. That is, the first lens 210 includes the above-described translucent member 110, the hard coat layer 120, and the antireflection layer 130.

Lens unit 200 further includes a lens barrel 202 and a filter 260. The first lens 210 , the second lens 220 , the third lens 230 , the fourth lens 240 , and the fifth lens 250 are installed in the lens barrel 202 . At least one of the first lens 210, the second lens 220, the third lens 230, the fourth lens 240, and the fifth lens 250 may be arranged such that at least a portion thereof is exposed from the lens barrel 202. For example, the first lens 210 is arranged so that at least a portion thereof is exposed from the lens barrel 202, and the other second lens 220, third lens 230, fourth lens 240, and fifth lens 250 are arranged inside the lens barrel 202. will be placed in

Note that the image sensor 270 may be arranged on the image side with respect to the filter 260 (lens unit 200). For example, as shown in FIG. 3, the image sensor 270 is placed outside the lens unit 200.

Filter 260 is arranged on the image side with respect to fifth lens 250. Filter 260 allows the wavelength of light that reaches image sensor 270 to be selected. The image sensor 270 is a photoelectric conversion element that converts irradiated light into an electrical signal. The image sensor 270 is, for example, a CMOS image sensor or a CCD image sensor. However, the image sensor 270 is not limited to these. The image sensor 270 captures an image of a subject formed by a plurality of lenses.

The first lens 210 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 210 is a spherical surface, and the concave image-side surface is an aspherical surface.

The second lens 220, the third lens 230, the fourth lens 240, and the fifth lens 250 may be made of resin (plastic lens) or glass.

The second lens 220, the third lens 230, the fourth lens 240, and the fifth lens 250 may be any of a biconvex lens, a plano-convex lens, a convex meniscus lens, and a concave meniscus lens.

Lens unit 200 is suitably used as an on-vehicle lens for photographing the surroundings of a vehicle. For example, the lens unit 200 is used as a vehicle-mounted lens for photographing the rear or side of a vehicle.

Since the first lens 210 includes the above-described translucent member 110, hard coat layer 120, and antireflection layer 130, ultraviolet rays entering the lens barrel 202 can be suitably suppressed. Therefore, even if a plastic lens is used as the lens in the lens barrel 202, deterioration of the plastic lens can be suppressed.

As described above, since the lens unit 200 includes a plurality of lenses and at least one lens of the plurality of lenses is the optical member 100, deterioration of the lenses in the lens unit 200 can be suppressed.

Further, the first lens 210 including the above-described translucent member 110, hard coat layer 120, and antireflection layer 130 is placed exposed from the lens barrel 202, and the remaining lenses (second lens 220, third lens 230, By arranging the fourth lens 240 and the fifth lens 250 in the lens barrel 202, it is possible to suppress deterioration of lenses other than the highly durable first lens 210.

First, the optical member 100 of Example 1 will be explained.

A translucent member 110 made of RM-104 manufactured by Nippon Shokubai Co., Ltd. was prepared. The light-transmitting member 110 was a meniscus lens with a convex surface facing the object side, and the outer diameter of the lens of the light-transmitting member 110 was about 14 mm.

A hard coat layer 120 was coated on the surface of the transparent member 110. The hard coat layer 120 was a photocurable resin material made of urethane or the like. The hard coat layer 120 is formed by applying a coating liquid to the transparent member 110 using a spin coating method, heating and drying the coating film made of the coating liquid, and then exposing the coating film to electromagnetic waves such as ultraviolet rays or electron beams. It was formed by curing.

The surface of the hard coat layer 120 was coated with an antireflection layer 130. The antireflection layer 130 was formed by alternately forming a high refractive index film made of Si ₃ N ₄ and a low refractive index film made of SiO ₂ by sputtering. In the optical member 100 of Example 1, eight high refractive index films and eight low refractive index films were alternately formed.

Table 1 shows the configuration of the antireflection layer 130 in the optical member 100 of Example 1.

In the optical member 100 of Example 1, the average reflectance in the wavelength range (300-400 nm) corresponding to the ultraviolet range is 40% or more, and the average reflectance in the wavelength range (450-800 nm) corresponding to the visible range is 2. The film thicknesses of the high refractive index film 130a and the low refractive index film 130b, of which the total number of films is 8, were set so that the total number of films was 0.0% or less. Here, the average reflectance was set at an incident angle of 5 degrees for each of ultraviolet light and visible light.

In the antireflection layer 130 of the optical member 100 of Example 1, the average reflectance in the ultraviolet region was 49.6%, and the average reflectance in the visible region was 1.0%. The optical member 100 of Example 1 can suppress the incidence of ultraviolet light. This makes it possible to suppress deterioration of the optical member 100 of Example 1 due to ultraviolet rays, thereby improving weather resistance.

Next, the optical member 100 of Example 1 was subjected to a thermal shock test of the optical member 100 and a weather resistance test of the antireflection layer 130 under the following conditions.

[Thermal shock test]
A thermal shock test was conducted using a thermal shock test device. In the thermal shock test, one cycle consisted of leaving the optical member 100 of Example 1 in a 85°C (high temperature) environment for 30 minutes and then in a -40°C (low temperature) environment for 30 minutes, and repeated 1000 cycles. Ta. During and after the thermal shock test, it was checked whether the antireflection layer 130 of the optical member 100 was peeled or cracked.

[Anti-reflection layer weather resistance test]
A weather resistance test was conducted using a highly accelerated weather resistance tester, a 7.5 kW super xenon weather meter. In the weather resistance test, one cycle consisted of irradiation + rain for 18 minutes, followed by irradiation for 102 minutes, at an irradiance of 180 W/m ² , and 500 cycles were repeated. During and after the weather resistance test, it was checked whether the antireflection layer 130 had peeled off.

Table 2 shows the results of the thermal shock test of the optical member 100 and the weather resistance test of the antireflection layer 130 of Example 1. In this specification, samples with no peeling or cracks in a visual inspection under a fluorescent lamp after a thermal shock test are indicated by ○, and samples with peeling or cracks are indicated by ×. Further, in this specification, after the weather resistance test, in a visual inspection under a fluorescent lamp, a sample with no peeling is indicated as "O", and a sample with peeling is indicated as "x".

As shown in Table 2, in the optical member 100 of Example 1, it was confirmed that the antireflection layer 130 did not peel off even after the thermal shock test and the weather resistance test.

In the same manner as the optical member 100 of Example 1, the optical members 100 of Examples 2 to 5 were manufactured. The optical members 100 of Examples 2 to 5 were also subjected to a thermal shock test and a weather resistance test in the same manner as the optical member 100 of Example 1.

Table 3 shows the structure of the antireflection layer 130 in the optical member 100 of Examples 1 to 5. In any of the optical members 100 of Examples 2 to 5, the film thicknesses of the high refractive index film 130a and the low refractive index film 130b of the antireflection layer 130 are such that light with a wavelength of 300 to 400 nm is incident at an incident angle of 5°. The average reflectance was set to be 40% or more when the wavelength was 450 to 800 nm, and the average reflectance was 2% or less when light with a wavelength of 450 to 800 nm was incident at an incident angle of 5°.

In the optical member 100 of Example 2, the total number of antireflection layers 130 is six. Again, the first film is the high refractive index film 130a, and the sixth film, which is the outermost film, is the low refractive index film 130b. The film thickness ratio is 1.2 or more and 2.6 or less.

In the optical member 100 of Example 3, the total number of antireflection layers 130 is eight. Again, the first film is the high refractive index film 130a, and the eighth film, which is the outermost film, is the low refractive index film 130b. The film thickness ratio is 1.1 or more and 2.4 or less.

In the optical member 100 of Example 4, the total number of antireflection layers 130 is eight. Again, the first film is the high refractive index film 130a, and the eighth film, which is the outermost film, is the low refractive index film 130b. The film thickness ratio is 1.1 or more and 2.5 or less.

In the optical member 100 of Example 5, the total number of antireflection layers 130 is ten. Again, the first film is the high refractive index film 130a, and the tenth film, which is the outermost film, is the low refractive index film 130b. The film thickness ratio is 1.1 or more and 5.9 or less.

Further, in the same manner as the optical member 100 of Example 1, optical members of Comparative Examples 1 to 7 were manufactured. The optical members of Comparative Examples 1 to 7 were also subjected to thermal shock tests and weather resistance tests in the same manner as the optical member 100 of Example 1.

Table 4 shows the structure of the antireflection layer in the optical members of Comparative Examples 1 to 7. In addition, in any of the optical members of Comparative Examples 1 to 6, the film thickness of the high refractive index film and the low refractive index film of the antireflection layer is the average thickness when light with a wavelength of 300 to 400 nm is incident at an incident angle of 5°. The reflectance was set to be 40% or more, and the average reflectance when light with a wavelength of 450 to 800 nm was incident at an incident angle of 5° was set to be 2% or less. However, in the optical member of Comparative Example 7, when light with a wavelength of 450-800 nm is incident at an incident angle of 5°, the average reflectance is 2% or less, while light with a wavelength of 300-400 nm is incident at an incident angle of 5°. The film thicknesses of the high refractive index film and the low refractive index film of the antireflection layer were set so that the average reflectance when the light was incident on the light was less than 40%.

In the optical member of Comparative Example 1, the total number of antireflection layers is five. The first film is a high refractive index film, and the fifth film, which is the outermost film, is a high refractive index film. The film thickness ratio is 1.1 or more and 5.8 or less.

In the optical member of Comparative Example 2, the total number of antireflection layers is eight. The first film is a high refractive index film, and the eighth film, which is the outermost film, is a low refractive index film. The film thickness ratio is 1.1 or more and 12.3 or less. Specifically, the film thickness ratio between the sixth film and the seventh film is 12.3, and the film thickness ratio between the seventh film and the eighth film is 8.8.

In the optical member of Comparative Example 3, the total number of antireflection layers is eight. Again, the first film is a high refractive index film, and the eighth film, which is the outermost film, is a low refractive index film. The film thickness ratio is 1.0 or more and 10.1 or less. Specifically, the film thickness ratio between the sixth film and the seventh film is 10.1.

In the optical member of Comparative Example 4, the total number of antireflection layers is eight. Again, the first film is a high refractive index film, and the eighth film, which is the outermost film, is a low refractive index film. The film thickness ratio is 1.1 or more and 8.6 or less. Specifically, the film thickness ratio between the fourth film and the fifth film is 8.6, and the film thickness ratio between the sixth film and the seventh film is 7.2.

In the optical member of Comparative Example 5, the total number of antireflection layers was 10. Again, the first film is a high refractive index film, and the tenth film, which is the outermost film, is a low refractive index film. The film thickness ratio is 1.2 or more and 6.7 or less. Specifically, the film thickness ratio between the first film and the second film is 6.7.

In the optical member of Comparative Example 6, the total number of antireflection layers was 10. Again, the first film is a high refractive index film, and the tenth film, which is the outermost film, is a low refractive index film. The film thickness ratio is 1.0 or more and 13.8 or less. Specifically, the film thickness ratio between the eighth film and the ninth film is 7.6, and the film thickness ratio between the ninth film and the tenth film is 13.8.

In the optical member of Comparative Example 7, the total number of antireflection layers is eight. Again, the first film is a high refractive index film, and the eighth film, which is the outermost film, is a low refractive index film. The film thickness ratio is 1.2 or more and 3.6 or less.

Next, Table 5 shows the configurations of the antireflection layers in the optical members 100 of Examples 1 to 5 and the optical members of Comparative Examples 1 to 6.

In the optical members 100 of Examples 1 to 5, no peeling occurred in the antireflection layer 130 even in the thermal shock test, but in the optical members of Comparative Examples 1 to 6, peeling occurred in the antireflection layer in the thermal shock test. did. Further, in the optical members 100 of Examples 1 to 5, no peeling occurred in the antireflection layer 130 even in the weather resistance test, but in the optical members of Comparative Examples 1 to 7, the antireflection layer 130 did not peel in the weather resistance test. There has occurred.

Note that the present technology can have the following configuration.
(1) A translucent member,
a hard coat layer covering the translucent member;
and an antireflection layer covering the hard coat layer,
The antireflection layer is configured such that high refractive index films and low refractive index films are alternately overlapped,
The high refractive index film contains Si ₃ N ₄ ,
The low refractive index film contains SiO ₂ ,
The total number of the high refractive index film and the low refractive index film is an even number,
For each of the high refractive index film and the low refractive index film in the antireflection layer, the ratio of the thickness of the thicker film to the thickness of the thinner film of two adjacent films is 6 times or less,
An optical member, wherein the antireflection layer has an average reflectance of 40% or more in a wavelength range of 300 to 400 nm.

(2) The optical member according to (1), wherein the total number of the high refractive index film and the low refractive index film is 10 or less.

(3) The optical member according to (1) or (2), wherein the total number of the high refractive index film and the low refractive index film is 6 or more and 8 or less.

(4) The optical member according to any one of (1) to (3), wherein the film located farthest from the hard coat layer among the antireflection layers is the low refractive index film.

(5) A lens unit comprising a plurality of lenses,
A lens unit, wherein at least one lens of the plurality of lenses is the optical member according to any one of (1) to (3).

(6) further comprising a lens barrel to which multiple lenses can be attached;
the at least one lens is arranged to be exposed from the lens barrel,
The lens unit according to (5), wherein the remaining lenses among the plurality of lenses are arranged within the lens barrel.

100 Optical member 110 Transparent member 120 Hard coat layer 130 Antireflection layer 130a High refractive index film 130b Low refractive index film

Claims (6)

a translucent member;
a hard coat layer covering the translucent member;
and an antireflection layer covering the hard coat layer,
The antireflection layer is configured such that high refractive index films and low refractive index films are alternately overlapped,
The high refractive index film contains Si ₃ N ₄ ,
The low refractive index film contains SiO ₂ ,
The total number of the high refractive index film and the low refractive index film is an even number,
For each of the high refractive index film and the low refractive index film in the antireflection layer, the ratio of the thickness of the thicker film to the thickness of the thinner film of two adjacent films is 6 times or less,
An optical member, wherein the antireflection layer has an average reflectance of 40% or more in a wavelength range of 300 to 400 nm. The optical member according to claim 1, wherein the total number of the high refractive index film and the low refractive index film is 10 or less. The optical member according to claim 2, wherein the total number of the high refractive index film and the low refractive index film is 6 or more and 8 or less. The optical member according to any one of claims 1 to 3, wherein a film located farthest from the hard coat layer among the antireflection layers is the low refractive index film. A lens unit comprising a plurality of lenses,
A lens unit, wherein at least one lens of the plurality of lenses is the optical member according to any one of claims 1 to 3. It also has a lens barrel to which multiple lenses can be attached,
the at least one lens is arranged to be exposed from the lens barrel,
The lens unit according to claim 5, wherein the remaining lenses among the plurality of lenses are arranged within the lens barrel.

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