KR20240009721A - Anti-reflection layer with scratch-resistance and lens having the same - Google Patents

Abstract

According to one embodiment, an anti-reflective coating is provided disposed on the surface of a transparent base. The anti-reflective coating includes a plurality of first material layers and second material layers alternating with the first material layers and having a higher refractive index than the first material layers, wherein the second material layers include at least one It includes a silicon nitride layer and a plurality of high refractive index material layers having a higher refractive index than the silicon nitride layer, and the high refractive index material layers include Nb2O5 or Ta2O5.

Description

Anti-reflective coating having anti-scratch function and lens having the same {ANTI-REFLECTION LAYER WITH SCRATCH-RESISTANCE AND LENS HAVING THE SAME}

The present invention relates to an anti-reflective coating and a lens having the same, and in particular, to an anti-reflective coating of a lens disposed on the outermost surface of an automobile camera or LIDAR.

Most vehicles are equipped with a large number of cameras or LIDAR. For example, self-driving vehicles will be equipped with a large number of cameras, including front and rear cameras as well as side cameras along with LIDAR. In particular, because autonomous vehicles operate using information detected by LiDAR and cameras, the performance of LiDAR and cameras is essential for the safe operation of the vehicle. Therefore, the performance of lidar and cameras needs to be maintained constant over a long period of time.

A LIDAR or camera includes a lens that passes light incident from the subject. Since the outer surface of a battlefield camera lens is exposed to the external environment, it is prone to scratches caused by foreign substances such as sand. Scratches formed on the lens surface degrade camera performance, and as a result, the car may incorrectly detect external objects and malfunction may occur.

Anti-scratch coatings may be used to prevent scratches on the lenses. Typically, an anti-reflective coating is applied to the lens surface, and an anti-scratch coating may be disposed on the anti-reflective coating.

However, applying anti-scratch coatings along with anti-reflective coatings complicates the lens manufacturing process. Patent Document 1 discloses a technology for applying an anti-reflection coating and increasing the thickness of material layers with a high refractive index to prevent scratches of the anti-reflection coating. However, when the thickness of the material layer having a high refractive index is increased, there is a disadvantage in that the reflectance increases and the anti-reflection performance deteriorates.

Meanwhile, Nb2O5 or Ta2O5 has low light absorption and high refractive index in the visible region, making it suitable as a high refractive index material layer for anti-reflection coating. However, these material layers have relatively low hardness and cannot be used in anti-reflective coatings that require scratch resistance.

(Patent Document 1) Republic of Korea Patent Publication No. 10-2022-0080442

The problem to be solved by the present invention is to provide an anti-reflective coating that can prevent scratches while maintaining a low reflectance and a lens having the same.

Another problem to be solved by the present invention is to provide an anti-reflective coating that contains Nb2O5 or Ta2O5 and can prevent scratches, and a lens having the same.

An anti-reflective coating according to an embodiment of the present invention is an anti-reflective coating disposed on a surface of a transparent base, comprising: a plurality of first material layers; and second material layers arranged alternately with the first material layers and having a higher refractive index than the first material layers, wherein the second material layers include at least one silicon nitride layer and a higher refractive index than the silicon nitride layer. It includes a plurality of high refractive index material layers having a high refractive index, wherein the high refractive index material layers include Nb2O5 or Ta2O5.

The anti-reflective coating may have an average reflectance of 0.5% or less within the range of 450 nm to 750 nm.

At least one of the second material layers may include at least one of the high refractive index material layers along with a silicon nitride layer.

In one embodiment, the silicon nitride layer can be sandwiched between two layers of high refractive index material.

In another embodiment, the layer of high refractive index material may be sandwiched between two silicon nitride layers.

The second material layers may be disposed between the first material layers.

The anti-reflective coating may not cause scratches in a pencil hardness test in which a 9H pencil is scratched with a force of 10N.

The first material layers may include SiO ₂ or MgF ₂ .

The first material layers and the second material layers may be deposited using sputtering or atomic layer deposition technology.

A lens according to an embodiment of the present invention may include a transparent base and the anti-reflection coating disposed on one or both sides of the transparent base.

According to embodiments of the present invention, an anti-reflective coating that prevents scratches and has a low reflectivity, and a lens including the same can be provided. In particular, an anti-reflection coating with high hardness and low reflectivity can be provided by using a material layer with a relatively high refractive index, such as Nb2O5 or Ta2O5, together with the silicon nitride layer.

1 is a schematic cross-sectional view illustrating a lens with an anti-reflection coating according to an embodiment of the present invention.
FIG. 2 is an enlarged schematic cross-sectional view of the anti-reflective coating of FIG. 1.
FIG. 3 is a schematic cross-sectional view enlarging a portion of FIG. 2 to illustrate an anti-reflection coating according to an embodiment of the present invention.
Figure 4 is a schematic cross-sectional view illustrating an anti-reflective coating according to another embodiment of the present invention.
Figure 5 is a schematic cross-sectional view illustrating an anti-reflective coating according to another embodiment of the present invention.
Figure 6 is a simulation graph for explaining the reflectance of an anti-reflective coating according to an embodiment of the present invention.
Figure 7A is a graph showing the reflectance of an anti-reflective coating applied on the convex surface of a lens.
Figure 7b is a graph showing the reflectance of an anti-reflective coating applied on the concave side of a lens.
Figure 8 is a photograph showing the results of a pencil hardness test of an anti-reflective coating according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The examples introduced below are provided as examples so that the idea of the present invention can be sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And in drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. Like reference numerals refer to like elements throughout the specification.

FIG. 1 is a schematic cross-sectional view illustrating a lens with an anti-reflective coating according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view enlarging the anti-reflective coating 30 of FIG. 1, and FIG. 3 is This is a schematic cross-sectional view enlarging a portion (H5) of FIG. 2.

1 to 3, the lens according to this embodiment includes a transparent base 21 and an anti-reflective coating 30.

Transparent base 21 may have a flat surface, a concave surface, or a convex surface. The transparent base 21 may be glass or quartz, but is not limited thereto. For example, the transparent base 21 may be transparent plastic.

The anti-reflective coating 30 is disposed on the transparent base 21 and includes first material layers (L1 to L6) and second material layers (H1 to H5). As shown in FIG. 2, the first material layers (L1 to L6) and the second material layers (H1 to H5) are alternately arranged.

In this embodiment, the anti-reflective coating 30 is shown and described as comprising six first material layers (L1-L6) and five second material layers (H1-H5), but the invention is not limited thereto. No. To obtain sufficient hardness to prevent scratches, the anti-reflective coating 30 may be formed with 7 or more layers, and further, with 9 or more layers, and to prevent light loss, it may be formed with 15 or less layers. Furthermore, the total thickness of the coating 30 may be 1 μm or less. In certain embodiments, it may consist of 12 layers, including 6 first layers of material and 6 layers of second material.

The second material layers (H1 to H5) have a relatively higher refractive index than the first material layers (L1 to L6). The first material layers (L1 to L6) may have a refractive index of less than 1.6, and the second material layers (H1 to H5) may have a refractive index of 2.2 or more. For example, the first material layers (L1 to L6) may be formed of SiO ₂ or MgF ₂ .

Meanwhile, the second material layers H1 to H5 include at least one silicon nitride layer and may further include Nb ₂ O ₅ and/or Ta ₂ O ₅ . In this embodiment, some of the second material layers (H1 to H5), such as H1, H3, and H4, may be a single layer of Nb ₂ O ₅ or Ta ₂ O ₅ , and the remaining portion, such as H2 or H5, may be a single layer of Nb 2 O 5 or Ta 2 O 5 . may be multiple layers as shown in FIG. 3.

Referring to FIG. 3, the silicon nitride layer 33 may be sandwiched between high refractive index material layers 31 having a higher refractive index. Here, the high refractive index material layer may be, for example, a Nb ₂ O ₅ layer or a Ta ₂ O ₅ layer. As the silicon nitride layer 33 is sandwiched between the high refractive index material layers 31, the overall average refractive index of the silicon nitride layer 33 and the high refractive material layers 31 can be increased.

In this embodiment, the silicon nitride layer 33 is described as being sandwiched between two high refractive index material layers 31, but the present invention is not limited thereto. For example, a layer of high refractive index material 31 may be sandwiched between two silicon nitride layers 33.

The silicon nitride layer 33 may be Si ₃ N ₄ , but is not limited to a silicon nitride layer with an exact stoichiometric ratio. Therefore, in this specification, the silicon nitride layer 33 includes a nitride layer lacking Si or N in Si3N4, and may also include other elements such as oxygen.

In this embodiment, H5 is shown as being formed of the silicon nitride layer 33 and the high refractive index material layers 31, but H2 may be formed of the silicon nitride layer 33 and the high refractive index material layers 31. Additionally, second material layers other than H2 and H5 may be formed to include high refractive index material layers together with the silicon nitride layer.

By alternately arranging first material layers (L1 to L6) and second material layers (H1 to H5) with different refractive indices, the anti-reflection coating 30 is 98% effective for light in the visible or near-infrared region detected by the image sensor. Light can be incident on the transparent base 21 with a transmittance of % or more, furthermore, 99% or more, and further, 99.5% or more. For example, the anti-reflection coating 30 can allow light to be incident on the transparent base 21 with a transmittance of 98% or more within a wavelength range of 450 nm to 750 nm. Therefore, when an anti-reflection coating is added to the lower surface of the transparent base 21, the lens can have a transmittance of at least 90% or more, and further, 95% or more.

Meanwhile, the anti-reflection coating 30 may have a reflectance of about 1% or less, and further, 0.5% or less of light in the visible region or near-infrared region detected by the image sensor. For example, the anti-reflection coating 30 may exhibit an average reflectance of 0.5% or less within a wavelength range of 450 nm to 750 nm. Furthermore, the anti-reflection coating 30 may exhibit an average reflectance of 1% or less, and further, an average of 0.5% or less within the wavelength range of 400 nm to 800 nm.

The first material layers (L1 to L6) and the second material layers (H1 to H5) may be deposited on the transparent base 21 using sputtering or atomic layer deposition technology. By using sputtering or atomic layer deposition technology, the hardness of the first material layers (L1 to L6) and the second material layers (H1 to H5) can be increased compared to the material layers deposited using the commonly used electron beam evaporation method. You can. Moreover, by using sputtering or atomic layer deposition technology, a silicon nitride layer, which is difficult to deposit using an electron beam evaporation method, can be deposited, thereby increasing the hardness of the anti-reflection coating 30. Furthermore, when depositing the first and second material layers using the electron beam evaporation method, a difference in thickness may occur between the center and the edge of a product such as a lens, but the first and second material layers can be deposited using sputtering or atomic layer deposition technology. By depositing layers, the difference in thickness between the material layers deposited at the center and the edge can be reduced.

Meanwhile, the first material layers L1 to L6 may have a thickness ranging from 10 nm to 200 nm. Within this thickness range, the first material layers L1 to L6 can be stably formed to a thickness required for the anti-reflection coating 30 using sputtering or atomic layer deposition technology.

The second material layers H1 to H5 may have a thickness ranging from 10 nm to 200 nm. Within this thickness range, the second material layers H1 to H5 can be stably formed using sputtering or atomic layer deposition technology to a thickness required for anti-reflection coating. When the second material layers (H1 to H5) are formed to a thickness exceeding 200 nm using sputtering or atomic layer deposition technology, the stress applied to the second material layer increases and cracks may be formed. Therefore, it is possible to prevent defects such as cracks from forming in each layer by ensuring that each of the second material layers (H1 to H5) does not exceed 200 nm.

In one embodiment, the last layer (L6) of the anti-reflective coating 30 may be the first material layer. The last layer (L6) of the anti-reflective coating 30 is exposed to the outside. The last first material layer (L6) may be thicker than the average thickness of the other first material layers (L1 to L5). Meanwhile, the first layer of the anti-reflective coating 30 may be a first material layer or a second material layer. The first layer of anti-reflective coating 30 may be in contact with the transparent base 21 .

According to this embodiment, at least one of the second material layers (H1 to H5) of the anti-reflection coating 30 includes a high refractive index material layer having a higher refractive index than the silicon nitride layer together with the silicon nitride layer, thereby maintaining a low reflectance. While doing so, it is possible to provide a high hardness anti-reflective coating (30). In particular, Nb2O5 or Ta2O5 has a high refractive index but relatively low hardness, so it has not been applied to anti-reflection coatings for camera lenses used in adverse conditions. However, the present invention allows them to be used in conjunction with a silicon nitride layer, thereby lowering the overall thickness of the anti-reflective coating.

Figure 4 is a schematic cross-sectional view illustrating an anti-reflective coating according to another embodiment of the present invention.

Referring to Figure 4, the anti-reflective coating according to this embodiment is generally similar to the anti-reflective coating described with reference to Figures 1 to 3, except that at least one of the second material layers (H5') is a silicon nitride layer (33). ) and a high refractive index material layer 31 having a higher refractive index.

Since the silicon nitride layer 33 and the high refractive index material layer 31 are the same as described in the previous embodiment, detailed description is omitted. Although the silicon nitride layer 33 is shown disposed on the high refractive index material layer 31, the reverse could also be true.

Figure 5 is a schematic cross-sectional view illustrating an anti-reflective coating 30' according to another embodiment of the present invention.

Referring to Figure 5, the anti-reflective coating 30' according to this embodiment is generally similar to the anti-reflective coating 30 described with reference to Figures 1 to 3, but has second material layers (H1, H2N, H3). , H4, H5N) are all formed as a single layer, at least one of the second material layers (H2N, H5N) is formed as a silicon nitride layer, and the remaining second material layers (H1, H3, H4) are formed as a single layer. The difference is that it is formed of a material layer having a higher refractive index than the silicon nitride layer, for example, an Nb2O5 layer or a Ta2O5 layer.

Since the silicon nitride layer and the high refractive index material layer are the same as described with reference to FIGS. 1 to 3, detailed description is omitted to avoid duplication.

Figure 6 is a simulation graph for explaining the reflectance of an anti-reflective coating according to an embodiment of the present invention.

An anti-reflection coating was placed on a glass substrate of infinite thickness as a transparent base, and the reflectance according to the wavelength was simulated and shown in a graph. The materials and design thickness of each layer are shown in Table 1 below. Meanwhile, as a comparative example, the reflectance according to the wavelength for the anti-reflection coating designed with SiO2 and Nb2O5 was simulated and shown in a graph, and the material and design thickness of each layer are shown in Table 2 below.

floor number ingredient Physical thickness (nm) note Board glass One SiO2 10 L1 2 Nb2O5 16.58 H1 3 SiO2 23 L2 4 Nb2O5 10.23
H2 5 Si3N4 57.15 6 Nb2O5 109.98 7 SiO2 27.54 L3 8 Nb2O5 15.26 H3 9 SiO2 148.16 L4 10 Nb2O5 11.1 H4 11 SiO2 35.25 L5 12 Nb2O5 36.47
H5 13 Si3N4 38.99 14 Nb2O5 25.56 15 SiO2 95.19 L6 air Coating overall thickness 660.46

floor number ingredient Physical thickness (nm) note Board glass One SiO2 11.69 L1 2 Nb2O5 25.49 H1 3 SiO2 18.22 L2 4 Nb2O5 135.82 H2 5 SiO2 30.91 L3 6 Nb2O5 17.43 H3 7 SiO2 102.99 L4 8 Nb2O5 14.6 H4 9 SiO2 39.74 L5 10 Nb2O5 116.8 H5 11 SiO2 91.21 L6 air Coating overall thickness 604.91

Referring to Tables 1 and 2, the examples include Si3N4 with layers corresponding to H2 and H5 of the comparative example sandwiched between Nb2O5 layers. That is, the comparative example is an anti-reflection coating in which SiO2 layers and Nb2O5 layers are alternately laminated, and the example is one in which a Si3N4 layer is inserted between the Nb2O5 layers corresponding to the second material layer.

Referring to FIG. 6, the anti-reflective coating of the example shows a low reflectance that is generally similar to the anti-reflective coating of the comparative example. All of these anti-reflective coatings showed less than 1% reflectivity in the simulation range from 400 nm to 800 nm.

The anti-reflective coating of the example included Si3N4, but showed an equally low reflectivity compared to the anti-reflective coating of the comparative example. Additionally, the anti-reflective coating of the embodiment may include Si3N4 to exhibit significantly higher hardness. On the other hand, the anti-reflection coating of the comparative example has relatively low hardness by adopting only low-hardness Nb2O5 layers as the high refractive index layer.

FIG. 7A is a graph showing the reflectance of an anti-reflective coating applied on a convex surface of a lens, and FIG. 7B is a graph showing the reflectance of an anti-reflective coating applied on a concave surface of a lens.

The anti-reflective coating was formed with the same target thickness on the convex upper surface and concave lower surface of the lens using sputtering technology to correspond to the thickness of the design layers in Table 1. Reflectance according to wavelength was measured at the center and edge areas of the lens and is shown in Figures 7a and 7b.

7A and 7B, the reflectance of the anti-reflective coating at the center (S1C1) and edge (S1L2) on the convex side and the center (S2C1) and edge (S2L2) on the concave side is approximately over 450 nm to 800 nm. It shows a value of less than 1%, and it can be seen that the reflectance is generally less than 0.5% in most wavelength ranges. The anti-reflection coating of this example had an average reflectance of less than 0.5% in the range of 450 nm to 750 nm, showing extremely low reflectance in most visible light regions.

Figure 8 is a photograph showing the results of a pencil hardness test of an anti-reflective coating according to an embodiment of the present invention.

An anti-reflective coating was deposited on the glass substrate using a sputtering technique to correspond to the thickness of the design layers in Table 1, and a 9H pencil hardness test was performed with a force of 10N.

Referring to Figure 8, no scratches occurred on the anti-reflective coating after the pencil hardness test.

The anti-reflective coating according to the present disclosure can achieve high hardness and low reflectance by using a silicon nitride layer such as Si3N4, which has relatively high hardness, together with an Nb2O5 or Ta2O5 layer that has relatively low hardness and a high refractive index. Moreover, the anti-reflective coating can be used to provide an anti-scratch function, simplifying the lens manufacturing process.

Although various embodiments have been described above, the present invention is not limited to these embodiments and may be modified in various ways without departing from the scope of the invention. In particular, although the lens surface treatment method is described in this specification, it can also be used as a surface treatment method for transparent substrates such as glass substrates in addition to lenses.

Claims (10)

An anti-reflective coating disposed on the surface of a transparent base, comprising:
a plurality of first material layers; and
Second material layers arranged alternately with the first material layers and having a higher refractive index than the first material layers,
The second material layers include at least one silicon nitride layer and a plurality of high refractive index material layers having a higher refractive index than the silicon nitride layer,
An anti-reflective coating wherein the high refractive index material layers include Nb2O5 or Ta2O5. In claim 1,
Anti-reflective coating with an average reflectance of 0.5% or less in the range of 450 nm to 750 nm. In claim 1,
At least one of the second material layers includes at least one of the high refractive index material layers together with a silicon nitride layer. In claim 3,
The silicon nitride layer is an anti-reflective coating sandwiched between two layers of high refractive index material. In claim 3,
The layer of high refractive index material is an anti-reflective coating sandwiched between two silicon nitride layers. In claim 1,
The second material layers are disposed between the first material layers. In claim 1,
Anti-reflective coating that does not scratch in a pencil hardness test where a 9H pencil is scratched with a force of 10N. In claim 1,
An anti-reflective coating wherein the first material layers include SiO ₂ or MgF ₂ . In claim 1,
An anti-reflective coating wherein the first and second material layers are deposited using sputtering or atomic layer deposition techniques. Transparent base: and
A lens comprising the anti-reflective coating of any one of claims 1 to 9 disposed on one or both sides of the transparent base.