Cover glass and imaging device

Abstract

Provided is a cover glass capable of effectively making it difficult for unnecessary light to be incident on an image sensor in an imaging device.　A cover glass 1 that is used in an imaging device and has a light-transmitting part 1A and a light-shielding part 1B adjacent to each other, the cover glass 1 comprising a glass substrate 2, a light-shielding film 3 that is provided on a main surface 2a of the glass substrate 2 in the light-shielding part 1B and contains chromium, and an anti-reflection film 4 that is provided on the main surface 2a of the glass substrate 2 in the light-transmitting part 1A, wherein: the light-shielding film 3 has a first main surface 3a that is arranged on the glass substrate 2 side, and a second main surface 3b that faces the first main surface 3a; and the second main surface 3b has a portion extending more to the light-transmitting part 1A side than the first main surface 3a on the glass substrate 2 side in a plan view.

Description

Cover glass and imaging device

[0001] The present invention relates to a cover glass and an imaging device using the cover glass.

[0002] Conventionally, imaging devices with an image sensor built into a housing have been widely used. When the image sensor receives unwanted light, such as light reflected within the housing of the imaging device, problems such as flare and ghosting can occur. To prevent such problems, a cover glass or the like having a light-shielding film provided on one main surface of a glass substrate is sometimes used. In this case, it is possible to shield the portions of the imaging device that do not need light to reach.

[0003] As an example of such a cover glass, Patent Document 1 below discloses an optical filter member in which a light-shielding film is formed in a peripheral region on the upper surface of a base. Also, Patent Document 2 below discloses a cover glass having a light-shielding portion and a light-transmitting portion, in which a light-shielding film and an anti-reflection film are laminated on the main surface of a glass substrate in the light-shielding portion.

[0004] JP 2014-170182 A JP 2021-092605 A

[0005] However, even with the cover glasses described in Patent Documents 1 and 2, it is still difficult to sufficiently suppress the incidence of unnecessary light on the image sensor in the imaging device, which makes it difficult to reliably prevent defects such as flare and ghosting in imaging devices that use such cover glasses.

[0006] An object of the present invention is to provide a cover glass that can effectively prevent unwanted light from entering an image sensor in an imaging device, and an imaging device using the cover glass.

[0007] Various aspects of the cover glass and imaging device that solve the above problems will be described.

[0008] A cover glass according to a first aspect of the present invention is used in an imaging device and has adjacent light-transmitting and light-shielding portions, and comprises a glass substrate; a light-shielding film containing chromium that is provided on a main surface of the glass substrate in the light-shielding portion; and an anti-reflection film that is provided on the main surface of the glass substrate in the light-transmitting portion, wherein the light-shielding film has a first main surface that is disposed on the glass substrate side and a second main surface that faces the first main surface, and the second main surface has a portion that, in a planar view, extends toward the light-transmitting portion beyond the first main surface on the glass substrate side.

[0009] The cover glass of Aspect 2 may be the same as Aspect 1, wherein the light-shielding film has a width that increases in a direction from a first main surface toward a second main surface on the glass substrate side at an end portion on the light-transmitting portion side.

[0010] The cover glass of Aspect 3 may be the same as Aspect 1 or 2, wherein a gap is provided between an end of the light-shielding film and the light-transmitting portion on the main surface of the glass substrate. In this case, it is preferable that the anti-reflection film is provided so as to fill the gap between the end of the light-shielding film and the light-transmitting portion.

[0011] The cover glass of Aspect 4 is any one of Aspects 1 to 3, and the anti-reflection film may also be provided on the light-shielding film.

[0012] In the cover glass of Aspect 5, in any one of Aspects 1 to 4, it is preferable that the thickness of the light-shielding film is 100 nm or more and 1000 nm or less.

[0013] The cover glass of Aspect 6 is any one of Aspects 1 to 5, wherein the light-shielding film may have a chromium layer provided on the main surface of the glass substrate and a chromium nitride layer provided on the chromium layer.

[0014] A cover glass of Aspect 7 is the cover glass of Aspect 6, wherein the light-shielding film may further include a chromium oxynitride layer provided on the chromium nitride layer.

[0015] An imaging device according to aspect 8 of the present invention comprises a housing having a bottom and a frame-shaped side wall, an image sensor provided on the bottom of the housing, and a cover glass according to any one of aspects 1 to 7 provided on the side wall of the housing, wherein the light-transmitting portion of the cover glass is positioned so as to overlap the image sensor in a planar view, the light-shielding portion of the cover glass is positioned so as not to overlap the image sensor in a planar view, and the light-shielding film and the anti-reflection film of the cover glass are positioned so as to face the image sensor.

[0016] According to the present invention, it is possible to provide a cover glass that can effectively prevent unwanted light from entering an image sensor in an imaging device, and an imaging device using the cover glass.

[0017] FIG. 1 is a schematic plan view showing a cover glass according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a portion of the cover glass of FIG. 1 taken along line X-X. FIG. 3 is a schematic cross-sectional view showing an enlarged view of a portion of the cover glass of FIG. 2 where a light-shielding film is provided. FIG. 4 is a schematic cross-sectional view showing an imaging device including a cover glass according to the first embodiment of the present invention. FIG. 5 is a photograph showing an edge of a light-shielding film produced in an experimental example. FIG. 6 is a photograph showing an anti-reflection film formed so as to cover the light-shielding film of FIG. 5. FIG. 7 is a schematic cross-sectional view showing a cover glass according to a second embodiment of the present invention. FIG. 8 is a schematic cross-sectional view showing a cover glass according to a third embodiment of the present invention. FIG. 9 is a schematic cross-sectional view showing an imaging device including a cover glass of a comparative example.

[0018] 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.

[0019] [First embodiment] Fig. 1 is a schematic plan view showing a cover glass according to a first embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of a portion of the cover glass of Fig. 1 taken along line X-X. Fig. 3 is a schematic cross-sectional view showing an enlarged view of a portion of the cover glass of Fig. 2 where a light-shielding film is provided.

[0020] The cover glass 1 is a cover glass used in an imaging device. The cover glass 1 has adjacent light-transmitting portion 1A and light-shielding portion 1B. The light-transmitting portion 1A is a portion that transmits light to an image sensor in the imaging device. The light-shielding portion 1B is a portion that blocks light that enters the imaging device. By providing the light-shielding portion 1B, it is possible to suppress the incidence of unnecessary light on the image sensor in the imaging device. As shown in FIG. 1 , the light-shielding portion 1B is provided in a peripheral region of the light-transmitting portion 1A in a plan view. However, the positional relationship between the light-transmitting portion 1A and the light-shielding portion 1B is not particularly limited.

[0021] 2 and 3, the cover glass 1 includes a glass substrate 2, a light-shielding film 3, and an anti-reflection film 4. The light-shielding film 3 is provided on a main surface 2a of the glass substrate 2.

[0022] The light-shielding film 3 is provided in a region overlapping with the light-shielding portion 1B in plan view. The anti-reflection film 4 is provided in a region overlapping with at least the light-transmitting portion 1A in plan view.

[0023] The light-shielding film 3 has a first main surface 3a and a second main surface 3b that face each other. The first main surface 3a of the light-shielding film 3 is in contact with the main surface 2a of the glass substrate 2. Therefore, the first main surface 3a of the light-shielding film 3 is provided on the glass substrate 2 side. The second main surface 3b of the light-shielding film 3 is provided on the outer side opposite to the glass substrate 2. In this embodiment, an anti-reflection film 4 is also provided on the second main surface 3b of the light-shielding film 3.

[0024] 2 and 3 , the second main surface 3 b of the light-shielding film 3 has a portion that extends further toward the light-transmitting portion 1A than the first main surface 3 a in a plan view. In particular, in this embodiment, the light-shielding film 3 is provided so that its end portion 3 c on the light-transmitting portion 1A side increases in width in a direction from the first main surface 3 a on the glass substrate 2 side toward the second main surface 3 b on the anti-reflection film 4 side.

[0025] The cover glass 1 of this embodiment has the above-described configuration, and therefore can effectively prevent unwanted light from being incident on the image sensor in an imaging device, as will be described in detail below.

[0026] FIG. 9 is a schematic cross-sectional view showing an imaging device equipped with a cover glass of a comparative example.

[0027] 9 , in the cover glass 101 of the comparative example, the main surface 102a of the glass substrate 102 on which the light-shielding film 103 and the anti-reflection film 104 are provided is disposed so as to face the image sensor 106. However, even in the imaging device 110 using such a cover glass 101, it is still difficult to sufficiently suppress the incidence of unnecessary light on the image sensor 106, and there is a problem in that it is difficult to more reliably prevent defects such as flare and ghosting.

[0028] As a result of extensive research into this issue, the present inventors have found that in cover glass 101 such as the comparative example, unwanted light A is reflected at end 103c on the light-transmitting portion 101A side of light-shielding film 103, and as a result, the reflected light A may enter image sensor 106. Therefore, the present inventors have found that the above problem can be solved by using a configuration such as cover glass 1 shown in Figure 4.

[0029] FIG. 4 is a schematic cross-sectional view showing an imaging device including a cover glass according to the first embodiment of the present invention.

[0030] As shown in Fig. 4, the imaging device 10 includes the cover glass 1 of this embodiment, a housing 5, and an image sensor 6. The housing 5 has a bottom 5a and a frame-shaped side wall 5b. The side wall 5b is provided on the bottom 5a. The cover glass 1 is provided on the side wall 5b so as to seal the internal space of the housing 5. This forms a housing that houses the image sensor 6. The image sensor 6 is located on the bottom 5a of the housing 5.

[0031] Furthermore, in the cover glass 1, the main surface 2a of the glass substrate 2 on which the light-shielding film 3 and the anti-reflection film 4 are provided is disposed so as to face the image sensor 6. In particular, in the cover glass 1, the second main surface 3b of the light-shielding film 3 on the image sensor 6 side has a portion that extends further toward the light-transmitting portion 1A side than the first main surface 3a on the glass substrate 2 side in a plan view, so that unwanted light A incident from the light-transmitting portion 1A side can be reflected at the end 3c of the light-shielding film 3 and propagated outward. As a result, in the imaging device 10 including the cover glass 1, it is possible to reliably prevent unwanted light A reflected at the end 3c of the light-shielding film 3 on the light-transmitting portion 1A side from being incident on the image sensor 6, and defects such as flare and ghosting can be more reliably prevented.

[0032] 2 and 3, the light-shielding film 3 is preferably provided so that its end 3c on the light-transmitting portion 1A side increases in width in the direction from the first main surface 3a on the glass substrate 2 side to the second main surface 3b on the anti-reflection film 4 side. In this case, it is possible to more reliably prevent unwanted light A from entering the image sensor.

[0033] Furthermore, in this embodiment, a gap 3d is provided on the main surface 2a of the glass substrate 2 between the end 3c of the light-shielding film 3 and the light-transmitting portion 1A, and the anti-reflection film 4 is provided to fill this gap 3d. This makes it possible to more reliably prevent unwanted light A from entering the image sensor. However, in the present invention, the anti-reflection film 4 does not necessarily have to be provided in the gap 3d between the end 3c of the light-shielding film 3 and the light-transmitting portion 1A.

[0034] Each component of the cover glass 1 will be described in detail below.

[0035] (Glass Substrate) 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 of the glass substrate 2 is not particularly limited.

[0036] The thickness of the glass substrate 2 can be appropriately set depending on the light transmittance, etc. The thickness of the glass substrate 2 is not particularly limited, and can be, for example, 0.1 mm to 1.2 mm.

[0037] The glass used for the glass substrate 2 is not particularly limited, but examples thereof include borosilicate glass, alkali-free glass, aluminosilicate glass, and quartz glass.

[0038] (Light-Shielding Film) As shown in Figure 3, the light-shielding film 3 has a chromium layer 3A, a chromium nitride layer 3B, and a chromium oxynitride layer 3C laminated in this order on the main surface 2a of the glass substrate 2. The chromium layer 3A is a film containing chromium as its main component. The chromium nitride layer 3B is a film containing chromium nitride as its main component. The chromium oxynitride layer 3C is a film containing chromium oxynitride as its main component. In this specification, a film containing a material as its main component refers to a film containing 50 mass% or more of that material, and it is preferable that the film containing a material as its main component be a film composed solely of that material, excluding impurities.

[0039] In the light-shielding film 3, the chromium layer 3A reflects light, thereby preventing unwanted light from entering the imaging device at the light-shielding portion 1B. The chromium nitride layer 3B is provided between the chromium layer 3A and the anti-reflection film 4 and functions as a reflectance adjustment layer. Specifically, the chromium nitride layer 3B acts as a low-refractive index layer, and reduces reflectance by optical interference in combination with the chromium layer 3A (high-refractive index layer). This more effectively prevents unwanted light reflected by the light-shielding film 3 from entering the image sensor. The chromium oxynitride layer 3C also functions as a reflectance adjustment layer. Therefore, the use of the chromium oxynitride layer 3C more effectively prevents unwanted light reflected by the light-shielding film 3 from entering the image sensor.

[0040] The light-shielding film 3 does not necessarily have to have the chromium oxynitride layer 3C. Alternatively, the light-shielding film 3 may have another chromium nitride layer, a chromium oxynitride layer, or the like between the chromium layer 3A and the glass substrate 2. For example, the light-shielding film 3 may be formed by stacking a chromium oxynitride layer, a chromium nitride layer, a chromium layer, a chromium nitride layer, and a chromium oxynitride layer in this order on the main surface 2a of the glass substrate 2. The light-shielding film 3 is not particularly limited as long as it contains chromium.

[0041] The thickness of each layer in the light-shielding film 3 is not particularly limited. The thickness of the chromium layer 3A can be, for example, 50 nm or more and 250 nm or less. The thickness of the chromium nitride layer 3B can be, for example, 15 nm or more and 80 nm or less. The thickness of the chromium oxynitride layer 3C can be, for example, 10 nm or more and 70 nm or less.

[0042] The overall thickness of the light-shielding film 3 is not particularly limited, but is preferably 100 nm or more, more preferably 150 nm or more, and even more preferably 200 nm or more, and is preferably 550 nm or less, more preferably 500 nm or less, and even more preferably 450 nm or less. In the cover glass 1, because the end 3c of the light-shielding film 3 has the above-described structure, even if the overall thickness of the light-shielding film 3 is increased, it is possible to effectively prevent unwanted light from entering the image sensor. Therefore, in the cover glass 1, the light-shielding film 3 can be designed to be thick.

[0043] (Anti-reflection film) The anti-reflection film 4 is a dielectric multilayer film formed by stacking a high-refractive index layer with a relatively high refractive index and a low-refractive index layer with a relatively low refractive index. By providing the anti-reflection film 4 in the light-transmitting portion 1A, it is possible to efficiently transmit the light required for the image sensor. Furthermore, by providing the anti-reflection film 4 in the light-shielding portion 1B, it is possible to more effectively prevent unwanted light reflected by the light-shielding film 3 from entering the image sensor.

[0044] The anti-reflection film 4 preferably has a portion where high-refractive index layers and low-refractive index layers are alternately stacked. In particular, it is more preferable that the high-refractive index layers and low-refractive index layers are all alternately stacked in the anti-reflection film 4. Furthermore, the anti-reflection film 4 is preferably stacked in order from the high-refractive index layers, but may be stacked in order from the low-refractive index layers. Note that the anti-reflection film 4 may be composed of functional films other than a dielectric multilayer film, as long as it has the above-mentioned functions.

[0045] 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.

[0046] The thickness of each layer in the antireflection film 4 is not particularly limited. The thickness of the high refractive index layer can be, for example, 1 nm or more and 150 nm or less. The thickness of the low refractive index layer can be, for example, 1 nm or more and 200 nm or less. The total thickness of the antireflection film 4 can be, for example, 50 nm or more and 400 nm or less.

[0047] The number of each layer in the antireflection film 4 is not particularly limited. The number of high refractive index layers can be, for example, 2 or more and 20 or less. The number of low refractive index layers can be, for example, 2 or more and 20 or less. Furthermore, the total number of stacked layers in the antireflection film 4 can be, for example, 4 or more and 40 or less.

[0048] An example of a method for manufacturing the cover glass 1 will now be described.

[0049] (Manufacturing Method) First, a glass substrate 2 is prepared. Next, a frame-shaped light-shielding film 3 is formed on the main surface 2a of the glass substrate 2 by positive photolithography.

[0050] Specifically, a chromium layer 3A, a chromium nitride layer 3B, and a chromium oxynitride layer 3C are formed in this order over the entire main surface 2a of the glass substrate 2. The method for forming the chromium layer 3A, the chromium nitride layer 3B, and the chromium oxynitride layer 3C is not particularly limited, and any conventionally known film formation method can be used. The chromium layer 3A, the chromium nitride layer 3B, and the chromium oxynitride layer 3C (hereinafter sometimes collectively referred to as chromium-containing layers) can be formed by, for example, a sputtering method or a vapor deposition method.

[0051] Next, a resist material (photosensitive material) is applied onto the glass substrate 2 on which the chromium-containing layer has been formed. The resist material can be applied by, for example, spin coating. Next, the glass substrate 2 after the resist material application is pre-baked to evaporate the solvent and solidify the resist material.

[0052] Next, the pattern depicted on the photomask is transferred by light irradiation onto the resist material fixed to the glass substrate 2. At this time, it is desirable to perform exposure (contact exposure) with the resist surface of the glass substrate 2 and the mask surface of the photomask in close contact with each other. Note that, for example, a glass mask can be used as the photomask.

[0053] Next, the exposed resist portion is removed using a developer. At this time, the exposed resist portion may be immersed in the developer by a surface dipping method in which the developer is pooled on the glass substrate 2 and treated for a predetermined time. After immersion in the developer, the exposed resist portion can be removed by rinsing with water and drying.

[0054] Next, the chromium-containing layer located on the exposed surface from which the resist portion has been removed is removed by etching.

[0055] Etching can be performed, for example, by a surface dipping method in which an etching solution is pooled on the glass substrate 2 and treated for a predetermined time. As the etching solution, for example, a liquid containing cerium ammonium nitrate, perchloric acid, acetic acid, nitric acid, etc. can be used.

[0056] The temperature of the etching solution can be, for example, 10° C. or higher and 50° C. or lower. The immersion time in the etching solution can be, for example, 1 minute or higher and 5 minutes or lower.

[0057] In the method for manufacturing the cover glass 1, by undergoing the etching step as described above, it is possible to form a structure in which the second main surface 3b of the light-shielding film 3 has a portion that extends further toward the light-transmitting portion 1A side than the first main surface 3a in a plan view. In particular, as shown in Figures 2 and 3, it is possible to form a structure in which the light-shielding film 3 has an end 3c on the light-transmitting portion 1A side that widens in the direction from the first main surface 3a on the glass substrate 2 side toward the second main surface 3b on the anti-reflection film 4 side.

[0058] Next, the resist material provided on the chromium-containing layer is peeled off, and the glass substrate 2 is washed, thereby forming a frame-shaped light-shielding film 3.

[0059] The resist material can be removed and the glass substrate 2 can be washed using an organic solvent such as N-methyl-2-pyrrolidone. The resist material can also be removed and the glass substrate 2 can be washed simultaneously by ultrasonic cleaning using the organic solvent.

[0060] Next, the anti-reflection film 4 is formed so as to cover the main surface 2a of the glass substrate 2 and the light-shielding film 3. In this way, the cover glass 1 can be formed.

[0061] The anti-reflection film 4 can be formed by alternately laminating high-refractive index layers and low-refractive index layers in this order. While it is preferable to laminate the anti-reflection film 4 starting with the high-refractive index layers, it is also possible to laminate the anti-reflection film 4 starting with the low-refractive index layers. The high-refractive index layers and the low-refractive index layers can be formed by vapor deposition, sputtering, CVD, or the like. In particular, it is preferable to form the high-refractive index layers and the low-refractive index layers by sputtering.

[0062] When the high refractive index layer and the low refractive index layer are formed by sputtering, the temperature of the glass substrate 2 can be set to, for example, 20° C. or higher and 300° C. or lower.

[0063] The high refractive index layer can be formed, for example, by using a target of the material that constitutes the high refractive index layer, setting the flow rate of an inert gas such as argon gas as a carrier gas to 50 sccm to 500 sccm, and applying power of 0.5 kW to 40 kW.

[0064] The low refractive index layer can be formed, for example, by using a target of the material that constitutes the low refractive index layer, setting the flow rate of an inert gas such as argon gas as a carrier gas to 50 sccm to 500 sccm, and applying power of 0.5 kW to 40 kW.

[0065] When forming the high-refractive-index layer and the low-refractive-index layer by sputtering, the deposition pressure is preferably 0.05 Pa or more and 0.8 Pa or less. Thus, when the deposition pressure is set high, the anti-reflection film 4 can also be formed in the gap 3d between the end 3c of the light-shielding film 3 and the light-transmitting portion 1A. This is thought to be because, when the deposition pressure is set high, the sputtered particles can be forced into the gap 3d between the end 3c of the light-shielding film 3 and the light-transmitting portion 1A due to collisions between the sputtered particles and the gas. Even when the deposition pressure is set low, the anti-reflection film 4 can also be formed in the gap 3d between the end 3c of the light-shielding film 3 and the light-transmitting portion 1A by setting the applied voltage high. The anti-reflection film 4 may also be formed in the gap 3d between the end 3c of the light-shielding film 3 and the light-transmitting portion 1A by other means for scattering sputtered particles in an oblique direction, such as by not providing a shielding plate in the sputtering apparatus.

[0066] A specific example of a method for manufacturing the cover glass 1 will be described below using an experimental example.

[0067] (Experimental Example) First, a chromium layer 3A, a chromium nitride layer 3B, and a chromium oxynitride layer 3C were formed in this order on the entire main surface 2a of a glass substrate 2 by a sputtering method. Next, a resist material (photosensitive material) was applied by a spin coating method onto the glass substrate 2 on which the chromium-containing layer had been formed. Next, the glass substrate 2 after the application of the resist material was pre-baked at 110°C for 90 seconds to evaporate the solvent and solidify the resist material.

[0068] Next, the pattern depicted on the photomask was transferred by light irradiation onto the resist material fixed to the glass substrate 2. At this time, contact exposure was performed with the resist surface of the glass substrate 2 and the mask surface of the photomask in close contact. A glass mask was used as the photomask. The light source used was light from an ultra-high pressure mercury lamp (dominant wavelengths: i-line (365 nm), h-line (405 nm), g-line (436 nm)).

[0069] Next, using a spray-type spin developer, the exposed resist portions were immersed in a developer by a surface dipping method in which the exposed resist portions were pooled in developer and treated for 1 minute. Tetramethylammonium hydroxide (TMAH, 2.38%) was used as the developer. After immersion in the developer, the glass substrate 2 was washed with water and dried to remove the exposed resist portions.

[0070] Next, the chromium-containing layer located on the exposed surface where the exposed resist portion was removed was removed by etching. Etching was performed using a spray-type spin developing device by a surface dipping method in which an etching solution was pooled on the glass substrate 2 and treated for 2 minutes. The etching solution used was a liquid containing 17% cerium ammonium nitrate and 5% nitric acid. The temperature of the etching solution was 30°C, and the substrate was immersed in the etching solution for 2 minutes.

[0071] Next, an ultrasonic cleaning device was used to remove the resist material provided on the chromium-containing layer and clean the glass substrate 2. As a result, a frame-shaped light-shielding film 3 was formed on the main surface 2a of the glass substrate 2. Note that N-methyl-2-pyrrolidone was used as a cleaning solution and to remove the resist material.

[0072] FIG. 5 is a photograph showing the edge of the light-shielding film produced in the experimental example.

[0073] As shown in Figure 5, it can be seen that the end 3c of the light-shielding film 3 produced in the experimental example has a structure in which the width increases in the direction from the first main surface 3a on the glass substrate 2 side toward the second main surface 3b on the outside.

[0074] Next, a sputtering method was used to form an antireflection film 4 so as to cover the main surface 2 a of the glass substrate 2 and the light-shielding film 3. Specifically, a high refractive index layer and a low refractive index layer were alternately laminated in this order on the light-shielding film 3 using a sputtering method, thereby forming the antireflection film 4.

[0075] During sputtering, a niobium (Nb) target was first sputtered using argon as a carrier gas to form a high refractive index layer (niobium oxide film) covering the main surface 2 a of the glass substrate 2 and the light-shielding film 3. The argon gas flow rate was 330 sccm, the target applied power (film-forming power) was 4 kW, and the film-forming pressure was 0.3 Pa. Next, a silicon (Si) target was sputtered using argon as a carrier gas to form a low refractive index layer (silicon oxide film) covering the high refractive index layer. The argon gas flow rate was 330 sccm, the target applied power (film-forming power) was 5 kW, and the film-forming pressure was 0.3 Pa. This operation was repeated to form a dielectric multilayer film (anti-reflection coating 4) having a total of six layers.

[0076] FIG. 6 is a photograph showing the anti-reflection film formed so as to cover the light-shielding film of FIG.

[0077] As shown in FIG. 6, it can be seen that the anti-reflection film 4 produced in the experimental example extends around to the end 3c of the light-shielding film 3 and is formed so as to fill the gap 3d at the end 3c of the light-shielding film 3.

[0078] Second Embodiment FIG. 7 is a schematic cross-sectional view showing a cover glass according to a second embodiment of the present invention.

[0079] 7, in the cover glass 21, the anti-reflection film 4 is not provided in the gap 3d formed between the end 3c of the light-shielding film 3 and the light-transmitting portion 1A. The other points are the same as those in the first embodiment.

[0080] In the second embodiment, the second main surface 3b of the light-shielding film 3 has a portion that extends toward the light-transmitting portion 1A more than the first main surface 3a in a planar view, thereby effectively preventing unnecessary light from entering the image sensor in the imaging device.

[0081] In the second embodiment, the anti-reflection film 4 is not provided in the gap 3d formed between the end 3c of the light-shielding film 3 and the light-transmitting portion 1A. In this case, since it is not necessary to scatter the sputtered particles in an oblique direction as in the first embodiment, it is possible to form a more uniform anti-reflection film 4 on the second main surface 3b of the light-shielding film 3 and the main surface 2a of the glass substrate 2.

[0082] When the antireflection film 4 is formed so as to fill the gap 3d formed between the end 3c of the light-shielding film 3 and the light-transmitting portion 1A as in the first embodiment, reflection at the interface between the light-shielding film 3 and air is less likely to occur compared to when the gap 3d is an air gap. Therefore, when the antireflection film 4 is formed so as to fill the gap 3d, it is possible to more reliably prevent unwanted light from entering the image sensor.

[0083] Third Embodiment FIG. 8 is a schematic cross-sectional view showing a cover glass according to a third embodiment of the present invention.

[0084] 8, in the cover glass 31, an anti-reflection film 34 is also provided on the main surface 2b on the other side of the glass substrate 2. The anti-reflection film 34 is provided directly on the main surface 2b of the glass substrate 2 in the light-transmitting portion 1A and the light-shielding portion 1B. Like the anti-reflection film 4, the anti-reflection film 34 is a dielectric multilayer film in which a high-refractive index layer and a low-refractive index layer are stacked in this order. Other points are the same as those in the first embodiment.

[0085] In the third embodiment, the second main surface 3b of the light-shielding film 3 has a portion that extends toward the light-transmitting portion 1A more than the first main surface 3a in a planar view, thereby effectively preventing unnecessary light from entering the image sensor in the imaging device.

[0086] As in the third embodiment, antireflection films 4, 34 may be provided on both main surfaces of the glass substrate 2. In this case, in the light-transmitting portion 1A, it is possible to more reliably allow light necessary for the image sensor to be incident on the image sensor, while more effectively preventing unwanted light from being incident on the image sensor due to reflection or the like.

[0087] In the present invention, in the light-shielding portion 1B, the light-shielding film 3 may be provided on both main surfaces of the glass substrate 2. Alternatively, another film different from the light-shielding film 3 and the anti-reflection films 4, 34 may be provided on at least one main surface of the glass substrate 2. The other film may be provided between the glass substrate 2 and the light-shielding film 3, or may be provided between the light-shielding film 3 and the anti-reflection film 4. Furthermore, the other film may be provided on the anti-reflection films 4, 34. As the other film, for example, an ultraviolet-shielding film, an infrared-shielding film, a band-pass filter, etc. may be used.

[0088] In the present invention, the antireflection film 4 may not be provided in the light-shielding portion 1B, and may be provided only in the light-transmitting portion 1A. The antireflection film 4 may be provided continuously from the main surface 2a of the glass substrate 2 in the light-transmitting portion 1A to the second main surface 3b of the light-shielding film 3 in the light-shielding portion 1B.

[0089] DESCRIPTION OF SYMBOLS 1, 21, 31...Cover glass 1A...Light-transmitting portion 1B...Light-shielding portion 2...Glass substrate 2a, 2b...Main surface 3...Light-shielding film 3a...First main surface 3b...Second main surface 3c...End portion 3d...Gap 3A...Chromium layer 3B...Chromium nitride layer 3C...Chromium oxynitride layer 4, 34...Anti-reflection film 5...Housing 5a...Bottom 5b...Side wall portion 6...Image sensor 10...Imaging device

Claims

1. A cover glass used in an imaging device, having adjacent light-transmitting and light-shielding portions, comprising: a glass substrate; a light-shielding film containing chromium, provided on a main surface of the glass substrate in the light-shielding portion; and an anti-reflection film provided on the main surface of the glass substrate in the light-transmitting portion, wherein the light-shielding film has a first main surface disposed on the glass substrate side and a second main surface opposing the first main surface, and the second main surface has a portion that extends toward the light-transmitting portion further than the first main surface on the glass substrate side in a plan view.

2. The cover glass according to claim 1, wherein the light-shielding film has a width that increases at the end on the light-transmitting portion side in a direction from the first main surface on the glass substrate side toward the second main surface.

3. A cover glass as described in claim 1 or 2, wherein a gap is provided on the main surface of the glass substrate between an end of the light-shielding film and the light-transmitting portion, and the anti-reflection film is provided so as to fill the gap between the end of the light-shielding film and the light-transmitting portion.

4. The cover glass according to claim 1 or 2, wherein the anti-reflection film is also provided on the light-shielding film.

5. The cover glass according to claim 1 or 2, wherein the thickness of the light-shielding film is 100 nm or more and 1000 nm or less.

6. The cover glass according to claim 1 or 2, wherein the light-shielding film comprises: a chromium layer provided on the main surface of the glass substrate; and a chromium nitride layer provided on the chromium layer.

7. The cover glass according to claim 6, wherein the light-shielding film further comprises a chromium oxynitride layer provided on the chromium nitride layer.

8. An imaging device comprising: a housing having a bottom and a frame-shaped side wall; an image sensor provided on the bottom of the housing; and a cover glass according to claim 1 or 2 provided on the side wall of the housing, wherein the light-transmitting portion of the cover glass is positioned so as to overlap with the image sensor in a planar view, the light-shielding portion of the cover glass is positioned so as not to overlap with the image sensor in a planar view, and the light-shielding film and the anti-reflection film of the cover glass are positioned so as to face the image sensor.

Images