Cover glass

Abstract

To provide a cover glass having excellent light-shielding property and low reflectance in a desired region.SOLUTION: A cover glass 1 used for an imaging device and having a light shielding part 1A and a light transmitting part 1B includes a glass base plate 2 having a first main surface 2a and a second main surface 2b facing each other, and a light shielding film 3 provided on the first main surface 1A of the glass base plate 2 in the light shielding part 2a. The light shielding film 3 includes an alloyed layer 3e made of metals containing chromium and niobium and a nitride layer 3d made of nitrides containing chromium and niobium, and the nitride layer 2a containing chromium and niobium is provided between the first main surface 3e and the alloyed layer 3d.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cover glass for use in an imaging device. [Background technology]

[0002] Conventionally, imaging devices with an image sensor built into a housing have been widely used. When the image sensor receives unnecessary light, such as light reflected inside the housing of the imaging device, problems such as flare and ghosting can occur. To prevent such problems, a cover glass or the like with a light-shielding film formed thereon is sometimes used. In this case, it is possible to block light from reaching portions of the imaging device that do not need to receive light. Patent Document 1 discloses an example of an optical filter member having a light-shielding film. In this optical filter member, the light-shielding film is formed in a peripheral region on the upper surface of a base. The upper surface of the base and the light-shielding film are covered with an optical multilayer film. The optical multilayer film has high transmittance for visible light and low transmittance for infrared light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-170182 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the optical filter member described in Patent Document 1 has a problem in that the light-shielding film not only has high light-shielding properties but also has high reflectivity. Therefore, for example, if light reflected from the surface of the light-shielding film is incident obliquely from the cover glass due to multiple reflections, the light may be reflected between the underside of the light-shielding film and the housing, resulting in unwanted light entering the image sensor. Another problem is low chemical durability against chemicals. An object of the present invention is to provide a cover glass that has excellent light-shielding properties in a desired region, low reflectivity, and high chemical durability. [Means for solving the problem]

[0005] A cover glass according to a first aspect of the present invention is a cover glass used in an imaging device, having a light-shielding portion and a light-transmitting portion, comprising a glass substrate having a first main surface and a second main surface facing each other, and a light-shielding film provided on the first main surface of the glass substrate in the light-shielding portion, wherein the light-shielding film includes an alloy layer made of a metal containing chromium and niobium, and a nitride layer made of a nitride containing chromium and niobium, and the nitride layer is provided between the first main surface and the alloy layer.

[0006] In the cover glass according to aspect 2, in aspect 1, it is preferable that the light-shielding film further includes an oxynitride layer made of an oxynitride containing chromium and niobium, and that the oxynitride layer is provided between the first main surface and the nitride layer.

[0007] In the cover glass according to aspect 3, in aspect 1 or aspect 2, it is preferable that the nitride layer is a first nitride layer, the light-shielding film further includes a second nitride layer made of a nitride containing chromium and niobium, and the alloy layer is provided between the first nitride layer and the second nitride layer.

[0008] In the cover glass of aspect 4, it is preferable that in aspect 3, the oxynitride layer is a first oxynitride layer, the light-shielding film further includes a second oxynitride layer made of an oxynitride containing chromium and niobium, and the second nitride layer is provided between the alloy layer and the second oxynitride layer.

[0009] In the cover glass according to aspect 5, in any one of aspects 1 to 4, it is preferable that the light-shielding portion further comprises an anti-reflection film, and that the light-shielding film is provided between the first main surface and the anti-reflection film.

[0010] A cover glass according to a sixth aspect of the present invention is the same as in the fifth aspect, but preferably has the anti-reflection film also provided on the first main surface of the glass substrate in the light-transmitting portion.

[0011] In the cover glass of aspect 7, in aspect 5 or aspect 6, it is preferable that the antireflection film is a first antireflection film, and that the cover glass further includes a second antireflection film provided on the second main surface of the glass substrate in the light-shielding portion and the light-transmitting portion. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a cover glass that has excellent light blocking properties in a desired region, low reflectance, and high chemical durability. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic front cross-sectional view of a cover glass according to a first embodiment of the present invention. [Figure 2] 1 is an enlarged schematic front cross-sectional view of a cover glass according to a first embodiment of the present invention. [Figure 3] 1 is a schematic front cross-sectional view of an imaging device having a cover glass according to a first embodiment of the present invention. [Figure 4] FIG. 4 is a schematic front cross-sectional view of a cover glass according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a schematic front cross-sectional view of a cover glass according to a third embodiment of the present invention. [Figure 6] 1 is a diagram showing the relationship between wavelength and reflectance at a light-shielding portion in Example 1 and Comparative Example 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0015] (First embodiment) Fig. 1 is a schematic front cross-sectional view of a cover glass according to a first embodiment of the present invention, and Fig. 2 is an enlarged schematic front cross-sectional view of the cover glass according to the first embodiment of the present invention.

[0016] The cover glass 1 shown in Figure 1 is used in an imaging device. The cover glass 1 has a light-shielding portion 1A and a light-transmitting portion 1B. The light-shielding portion 1A blocks light from entering the imaging device. This prevents the image sensor of the imaging device from receiving unnecessary light.

[0017] The cover glass 1 includes a glass substrate 2 and a light-shielding film 3. The glass substrate 2 has a first main surface 2a and a second main surface 2b that face each other. The light-shielding film 3 is provided on the first main surface 2a of the glass substrate 2. The specific configuration of the cover glass 1 will be described below.

[0018] The glass substrate 2 has a first region 2A and a second region 2B. The first region 2A is located in the light-shielding portion 1A of the cover glass 1, and the second region 2B is located in the light-transmitting portion 1B of the cover glass 1. In this embodiment, the first region 2A is a peripheral region surrounding the second region 2B. Note that the positional relationship between the first region 2A and the second region 2B is not limited to the above.

[0019] The glass used for the glass substrate 2 is not particularly limited, but examples thereof include borosilicate glass, alkali-free glass, and aluminosilicate glass. In this embodiment, the glass substrate 2 has a substantially rectangular plate shape. However, the glass substrate 2 may have a substantially circular plate shape, and the shape is not particularly limited.

[0020] The thickness of the glass substrate 2 can be set appropriately depending on the light transmittance, etc. The thickness of the glass substrate 2 can be, for example, about 0.2 mm to 1.2 mm. However, the thickness of the glass substrate 2 is not limited to the above.

[0021] The light-shielding film 3 is provided on the first main surface 2a in the first region 2A of the glass substrate 2. Here, as shown in Fig. 2, the light-shielding film 3 has an oxynitride layer 3c, a nitride layer 3d, and an alloy layer 3e stacked in this order from the glass substrate 2 side.

[0022] The alloy layer 3e is made of a metal containing chromium and niobium. The niobium content in the alloy layer 3e is preferably 30% or more and 70% or less in cation %. The lower limit is preferably 35% or more, 40% or more, 45% or more, and particularly 50% or more. The upper limit is preferably 65% ​​or less, 60% or less, and particularly 55% or less. This can improve the chemical durability of the alloy layer 3e.

[0023] The nitride layer 3d is made of a nitride containing chromium and niobium. The niobium content in the nitride layer 3d is preferably 30% or more and 70% or less in cation %. The lower limit is preferably 35% or more, 40% or more, 45% or more, and particularly 50% or more. The upper limit is preferably 65% ​​or less, 60% or less, and particularly 55% or less. This can improve the chemical durability of the nitride layer 3d.

[0024] The oxynitride layer 3c is made of an oxynitride containing chromium and niobium. The niobium content in the oxynitride layer 3c is preferably 30% or more and 70% or less in cation %. The lower limit is preferably 35% or more, 40% or more, 45% or more, and particularly 50% or more. The upper limit is preferably 65% ​​or less, 60% or less, and particularly 55% or less. This can improve the chemical durability of the oxynitride layer 3c.

[0025] Elemental analysis can be carried out, for example, by energy dispersive X-ray spectroscopy (SEM-EDX).

[0026] The light-shielding film 3 does not necessarily have to include the oxynitride layer 3c. Alternatively, the light-shielding film 3 may have another nitride layer, oxynitride layer, or the like stacked on the side of the alloy layer 3e opposite to the first main surface 2a of the glass substrate.

[0027] The thickness of the alloy layer 3e in the light-shielding film 3 can be, for example, about 50 nm to 250 nm. The thickness of the nitride layer 3d can be, for example, about 15 nm to 80 nm. The thickness of the oxynitride layer 3c can be, for example, about 10 nm to 70 nm. The thickness of each layer in the light-shielding film 3 is not limited to the above.

[0028] A feature of this embodiment is that the light-shielding film 3 provided on the glass substrate 2 is composed of an alloy layer 3e and a nitride layer 3d. This allows the cover glass 1 to have excellent light-shielding properties and low reflectance in the first region 2A. Furthermore, when this cover glass 1 is used in an imaging device, it is possible to effectively prevent unwanted light from entering the image sensor of the imaging device. This will be described in detail below.

[0029] FIG. 3 is a schematic front cross-sectional view of an imaging device having a cover glass according to a first embodiment of the present invention. As shown in FIG. 3, an imaging device 10 includes a cover glass 1 according to this embodiment, a housing 4, an image sensor 5, a lens barrel 7, and a lens 8. The housing 4 has a bottom 4a and a sidewall 4b. The sidewall 4b is provided on the bottom 4a. The cover glass 1 is provided on the sidewall 4b so as to seal the internal space of the housing 4. The image sensor 5 is disposed on the bottom 4a of the housing 4. The lens barrel 7 is provided on the second main surface 2b of the glass substrate 2 of the cover glass 1. Note that the lens barrel 7 does not have to be provided directly on the cover glass 1, and may be held by another holding member or the like. The lens 8 is held within the lens barrel 7.

[0030] 3, of the first main surface 2a and the second main surface 2b of the glass substrate 2, the first main surface 2a on which the light-shielding film 3 is provided is the main surface on the image sensor 5 side. In this way, the light-shielding film 3 is preferably provided on the main surface of the glass substrate 2 on the image sensor 5 side.

[0031] In the present embodiment shown in FIG. 3 , the alloy layer 3e in the light-shielding film 3 blocks light B, thereby preventing unwanted light B from entering the imaging device 10. By configuring the first region 2A as the light-shielding portion 1A, the light-shielding property in the first region 2A can be improved. In this case, if the reflectance of unwanted light B is high, light B reflected from the cover glass side is further reflected from the lens 8, increasing the possibility that unwanted light will enter the image sensor 5. The light-shielding film 3 of this embodiment is composed of the nitride layer 3d and the alloy layer 3e, in that order from the first principal surface 2a side. Therefore, the reflectance of the portion 2A of the first principal surface 2a where the light-shielding film 3 is provided is low when viewed from the second principal surface 2b side. This reduces the possibility that unwanted light will enter the image sensor.

[0032] Furthermore, in this embodiment, the light-shielding film 3 includes not only the alloy layer 3e but also a nitride layer 3d. The nitride layer 3d is provided between the alloy layer 3e and the glass substrate 2. This nitride layer 3d functions as a reflectance adjustment layer. Specifically, the nitride layer 3d acts as a low-refractive index layer, and optical interference occurs in combination with the alloy layer (high-refractive index layer), thereby further suppressing stray light from being reflected from the light-shielding portion 1A of the cover glass 1 toward the internal space of the housing 4. As such, the cover glass 1 is excellent in both light-shielding properties and low reflectivity. Therefore, when used in the imaging device 10, it is possible to effectively suppress unwanted light from entering the image sensor 5.

[0033] The light-shielding film 3 preferably has an oxynitride layer 3c provided between the nitride layer 3d and the glass substrate 2. In this case, the oxynitride layer 3c functions as a reflectance adjusting layer in addition to the nitride layer 3d, so that the reflectance of the light-shielding portion 1A of the cover glass 1 can be further reduced.

[0034] In the light-shielding film 3, an oxynitride layer 3c, a nitride layer 3d, an alloy layer 3e, a nitride layer 3b, and an oxynitride layer 3a may be stacked in this order from the glass substrate 2 side. The nitride layer 3d corresponds to the first nitride layer in the present invention, and the nitride layer 3b corresponds to the second nitride layer in the present invention. The oxynitride layer 3c corresponds to the first oxynitride layer in the present invention, and the oxynitride layer 3a corresponds to the second nitride layer in the present invention. This allows the second nitride layer to function as a low-refractive-index layer, and the second oxynitride layer to function as a reflectance-adjusting layer, thereby reducing the reflectance of the cover glass 1 in the light-shielding portion 1A when viewed from the first main surface 2a of the glass substrate 2. While the light-shielding portion 1A can have a low reflectance when viewed from the first main surface 2a of the glass substrate 2 without the second oxynitride layer, the presence of the second oxynitride layer further reduces the reflectance.

[0035] The cover glass according to the present invention can also be used in light-emitting parts of an imaging device. For example, if the imaging device has a viewfinder, a display element such as a display may be used in the viewfinder. The cover glass according to the present invention can also be used in the display element of the imaging device.

[0036] When the cover glass 1 is used in a display element, the high light-shielding properties of the light-shielding film 3 in the light-shielding portion 1A can suppress the emission of unnecessary light, and unnecessary parts such as wiring can be hidden from the outside. In addition, the cover glass 1 has low reflectivity in the light-shielding portion 1A. This makes it difficult for light to be reflected in the light-shielding portion 1A, preventing unnecessary light from being reflected within the display element and emitting from the light-transmitting portion 1B. This can also improve the uniformity of light in the display element.

[0037] (Second embodiment) 4 is a schematic front cross-sectional view of a cover glass according to a second embodiment of the present invention. As shown in Fig. 4, the cover glass 1 includes an anti-reflection film 6. The configuration of the light-shielding film 3 is the same as in the first embodiment.

[0038] The antireflection film 6 covers the light-shielding film 3 and is provided directly on the first main surface 2a in the second region 2B of the glass substrate 2. Note that the antireflection film 6 does not necessarily have to be provided on the first main surface 2a of the glass substrate 2 in the second region 2B. It is sufficient that the antireflection film 6 covers the light-shielding film 3. The antireflection film 6 is a dielectric multilayer film in which a high refractive index layer and a low refractive index layer are stacked.

[0039] Examples of materials for the high refractive index layer include niobium oxide, titanium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silicon nitride, and aluminum nitride. Examples of materials for the low refractive index layer include silicon oxide and aluminum oxide.

[0040] The thickness of the high refractive index layer can be, for example, about 1.5 nm to 150 nm. The thickness of the low refractive index layer can be, for example, about 1.5 nm to 150 nm. The thickness of each layer in the antireflection film 6 is not limited to the above.

[0041] In the present embodiment shown in FIG. 4 , the alloy layer 3e in the light-shielding film 3 reflects light B, thereby preventing unwanted light B from entering the imaging device 20. By configuring the first region 2A as the light-shielding portion 1A, the light-shielding property in the first region 2A can be improved. However, unwanted light A may still enter the imaging device 20 obliquely. In response to this, in the cover glass 1, the light-shielding film 3 is covered with an anti-reflection film 6. This prevents light A from being reflected from the light-shielding portion 1A of the cover glass 1 toward the internal space of the housing 4, thereby preventing reflection of light A within the imaging device 10.

[0042] As in this embodiment, the anti-reflection film 6 is preferably provided on the first main surface 2a of the glass substrate 2 in the second region 2B. This makes it possible to suppress the reflection of light from the light-transmitting portion 1B of the cover glass 1 toward the internal space of the housing 4. This further suppresses the incidence of unnecessary light on the image sensor 5. Furthermore, because the reflection of incident light can be suppressed at the light-transmitting portion 1B, the light necessary for imaging can easily enter the image sensor 5.

[0043] (Third embodiment) Fig. 5 is a schematic front cross-sectional view of a cover glass according to a third embodiment of the present invention. As shown in Fig. 5, the cover glass 30 includes a first antireflection film 6A. The first antireflection film 6A is the same as the antireflection film 6 in the first embodiment. This embodiment differs from the second embodiment in that it includes a second antireflection film 6B. The configuration of the light-shielding film 3 is the same as in the first embodiment.

[0044] The second antireflection film 6B is provided directly on the second main surface 2b in the first region 2A and the second region 2B of the glass substrate 2. Like the first antireflection film 6A, the second antireflection film 6B is a dielectric multilayer film in which high-refractive index layers and low-refractive index layers are stacked.

[0045] In the cover glass 30 of this embodiment, a second antireflection film 6B is provided on the second main surface 2b of the glass substrate 2. This makes it possible to prevent light B from being reflected from the cover glass 30 toward the lens 8 when used in an imaging device such as that shown in FIG. 3. This prevents light B reflected from the cover glass 30 from being further reflected from the lens 8, resulting in unnecessary light being incident on the image sensor 5.

[0046] [Example] Cover glasses of Example 1 and Comparative Example 1 shown below were prepared, and the reflectances at the light-shielding portions were compared.

[0047] Example 1 A cover glass of Example 1 having the configuration shown in FIG. 1 was fabricated. First, a frame-shaped light-shielding film was formed on the first main surface of a glass substrate by a lift-off method. Specifically, a resist pattern was formed on the first main surface of the glass substrate. Next, an oxynitride layer made of niobium chromium oxynitride (NbCrON), a nitride layer made of niobium chromium nitride (NbCrN), and an alloy layer made of niobium chromium alloy (NbCr) were laminated in this order on the first main surface by a sputtering method so as to cover the resist pattern. Thereafter, the resist pattern was peeled off to form a light-shielding film. The alloy layer had a thickness of 150 nm, the nitride layer had a thickness of 50.6 nm, and the oxynitride layer had a thickness of 31.4 nm.

[0048] (Comparative Example 1) A cover glass was obtained in the same manner as in Example 1, except that the light-shielding film was made of a chromium oxynitride (CrON) layer, a chromium nitride (CrN) layer, and a chromium (Cr) layer from the substrate side.

[0049] (evaluation) The reflectance of the light-shielding portion was compared between Example 1 and Comparative Example 1. Here, the reflectance of the light-shielding portion was measured when the cover glass was viewed from the second main surface 2b side. The reflectance of the light-shielding portion was measured using a spectrophotometer U-4100 manufactured by Hitachi High-Tech Science Corporation at an incident angle of 5°.

[0050] Tables 1 and 2 show the conditions of Example 1 and Comparative Example 1 and the average reflectance of the light-shielding part in the wavelength range of 430 nm to 680 nm, respectively.

[0051] [Table 1]

[0052] [Table 2] FIG. 6 is a diagram showing the relationship between wavelength and reflectance at the light-shielding portion in Example 1 and Comparative Example 1. In FIG.

[0053] It can be seen from Tables 1 and 2 that the average reflectance of the light-shielding portion in the wavelength range of 430 nm to 680 nm is 0.88% lower in Example 1 than in Comparative Example 1. Therefore, when the cover glass of the present application is used in an imaging device as shown in Figures 5 and 6, the cover glass of Example 1 can prevent stray light from reflected light from the lens side from reaching the image sensor. [Explanation of symbols]

[0054] 1. Cover glass 1A...Light blocking section 1B…Transparent part 2...Glass substrate 2A...First Area 2B...Second Area 2a...first principal surface 2b...Second main surface 3...Light-shielding film 3c...oxynitride layer 3d…Nitride layer 3e…alloy layer 4. Housing 4a...Bottom 4b…Side wall 5...Image sensor 6…Anti-reflection film 6A...First anti-reflection coating 6B...Second anti-reflection coating 7...Telescope tube 8...Lens 10...imaging device 20...imaging device 30...Cover glass

Claims

1. A cover glass used in an imaging device, the cover glass having a light-shielding portion and a light-transmitting portion, a glass substrate having a first main surface and a second main surface facing each other; the light-shielding portion includes a light-shielding film provided on the first main surface of the glass substrate, the light-shielding film includes an alloy layer made of a metal containing chromium and niobium, and a nitride layer made of a nitride containing chromium and niobium, The cover glass, wherein the nitride layer is provided between the first main surface and the alloy layer.

2. the light-shielding film further includes an oxynitride layer made of an oxynitride containing chromium and niobium, The cover glass of claim 1 , wherein the oxynitride layer is disposed between the first major surface and the nitride layer.

3. the nitride layer is a first nitride layer; the light-shielding film further includes a second nitride layer made of a nitride containing chromium and niobium, The cover glass of claim 2 , wherein the alloy layer is disposed between the first nitride layer and the second nitride layer.

4. the oxynitride layer is a first oxynitride layer, the light-shielding film further includes a second oxynitride layer made of an oxynitride containing chromium and niobium, The cover glass of claim 3 , wherein the second nitride layer is disposed between the alloy layer and the second oxynitride layer.

5. The light-shielding portion further includes an anti-reflection film, The cover glass according to claim 1 , wherein the light-shielding film is provided between the first main surface and the anti-reflection film.

6. The cover glass according to claim 5 , wherein the anti-reflection film is also provided on the first main surface of the glass substrate in the light-transmitting portion.

7. the antireflection film is a first antireflection film, The cover glass according to claim 5 , further comprising a second anti-reflection film provided on the second main surface of the glass substrate in the light-shielding portion and the light-transmitting portion.

Images