Anti-reflective cover glass

Abstract

The present invention pertains to an antireflection-film-equipped glass covering that is a glass covering provided with an antireflection film. The antireflection film is formed by alternately layering high refractive index layers and low refractive index layers. The outermost layer of the antireflection film is a low refractive index layer, and the total number of layers of the high refractive index layers and low refractive index layers is five or more. The thickness of the low refractive index layer which is the third layer from the outermost side of the antireflection film is no more than 35nm, and the thickness of the low refractive index layer which is the fifth layer from the outermost side is no more than 15nm.

Description

[Technical Field]

[0001] The present invention relates to a cover glass with an anti-reflection film. [Background technology]

[0002] In-vehicle information devices such as car navigation systems and audio equipment, as well as mobile communication devices, are equipped with display devices. Display devices are provided with protective covers such as cover glass to protect the display panel from external impact. An anti-reflection film may also be provided on the surface of the protective cover to reduce external light reflection.

[0003] Furthermore, a light-shielding layer, for example, in a frame shape, is provided on the surface of the protective cover facing the display panel. In addition to providing aesthetic benefits, the light-shielding layer also has the functions of concealing wiring on the display panel side and shielding illumination light from the backlight to prevent the illumination light from leaking around the display panel.

[0004] In such display devices, signage, etc., an infrared sensor 4 is incorporated in the display area or in the vicinity thereof, as shown in Fig. 1, for example, in order to perform communication and object detection using infrared light, specifically for the purposes of driver monitoring, fingerprint detection, touch sensor, gesture sensing, etc. However, due to the infrared light transmittance of the protective cover, specifically the cover glass 2 with the anti-reflection coating 1, the transmittance of the sensing light and signal light used in the infrared sensor 4 decreases, causing the sensor to malfunction or cause errors.

[0005] Therefore, a structure is known in which an infrared sensor can be installed on the back side of the light-shielding layer while making the infrared-transmitting layer less noticeable by opening a part of the light-shielding layer arranged in a frame shape and providing an infrared-transmitting layer, which is an area through which infrared rays can pass (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2017-49469 [Patent Document 2] Japanese Patent No. 5392641 Summary of the Invention [Problem to be solved by the invention]

[0007] However, as shown in Figure 1, drilling holes in the cover glass 2 to create openings would detract from the design, even in the frame-shaped light-blocking layer area. There is also concern that drilling holes will increase costs.

[0008] In contrast, the present invention aims to provide a cover glass with an anti-reflection film that suppresses infrared light reflectance while maintaining suppression of visible light reflectance without forming an opening, and that has high infrared light transmittance. [Means for solving the problem]

[0009] The inventors discovered that the above problem can be solved by setting the thickness of the low refractive index layer at a specific position among the high refractive index layer and low refractive index layer that make up the anti-reflection film to a certain value or less, and thus completed the present invention.

[0010] That is, one aspect of the present invention is as follows. [1] A cover glass provided with an anti-reflection coating, the anti-reflection coating being formed by alternately stacking high-refractive index layers and low-refractive index layers, the outermost layer of which is a low-refractive index layer, the total number of stacked high-refractive index layers and low-refractive index layers being 5 or more, the thickness of the low-refractive index layer positioned third from the outermost layer being 35 nm or less, and the thickness of the low-refractive index layer positioned fifth from the outermost layer being 15 nm or less. [2] The cover glass with an anti-reflection film according to [1], wherein the anti-reflection film has a visible light reflectance of 0.4% or less at a wavelength of 550 nm and an infrared light reflectance of 5% or less at a wavelength of 950 nm. [3] The cover glass with anti-reflection coating according to [1] or [2], wherein the refractive index of the high refractive index layer at a wavelength of 550 nm is 1.9 or more, and the refractive index of the low refractive index layer at a wavelength of 550 nm is 1.6 or less. [4] The cover glass with anti-reflection coating according to any one of [1] to [3] above, wherein the high refractive index material constituting the high refractive index layer is an oxide of at least one selected from the group consisting of Mo, W, Mg, Si, Nb, Ti, Zr, Ta, Al, Sn and In. [5] The cover glass with anti-reflection coating according to any one of [1] to [4], wherein the low refractive index material constituting the low refractive index layer is at least one selected from the group consisting of SiO2, MgF2, a material containing a mixed oxide of Si and Sn, a material containing a mixed oxide of Si and Zr, and a material containing a mixed oxide of Si and Al. [6] The cover glass with anti-reflection coating according to any one of [1] to [5] above, which is used together with an infrared sensor and has no opening at a location through which light entering and leaving the infrared sensor passes. [7] A display device comprising an infrared sensor and the cover glass with anti-reflection film according to any one of [1] to [6] above. [Effects of the Invention]

[0011] According to the present invention, a cover glass with an anti-reflection film can be obtained that has reduced reflectance not only for visible light but also for infrared light. By applying such a cover glass with an anti-reflection film to a display device, it is possible to provide an in-vehicle display device, a mobile display device, a signage, etc., which can increase infrared light transmittance and maintain excellent visibility while effectively preventing malfunction of the infrared sensor. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of a display device as an example of the prior art. [Figure 2] FIG. 2 is a schematic cross-sectional view of a display device to which a cover glass with an anti-reflection film according to one embodiment of the present invention is applied. [Figure 3] FIG. 3 is a schematic cross-sectional view showing the configuration of an antireflection film according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified as desired without departing from the spirit of the present invention. Furthermore, the symbol "to" indicating a numerical range is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0014] <Cover glass with anti-reflective coating> The cover glass with an anti-reflection film according to this embodiment has an anti-reflection film on the surface of the cover glass. 3, the antireflection film 1 is formed by alternately stacking high-refractive index layers and low-refractive index layers, with the outermost layer being low-refractive index layer 11. The total number of stacked high-refractive index layers and low-refractive index layers is 5 or more, the thickness of low-refractive index layer 12, which is the third layer from the outermost layer, is 35 nm or less, and the thickness of low-refractive index layer 13, which is the fifth layer from the outermost layer, is 15 nm or less.

[0015] [Anti-reflective film] In the anti-reflection coated cover glass, the anti-reflection coating 1 is disposed on the surface of the cover glass 2. The anti-reflection coating is formed by alternately laminating high-refractive index layers and low-refractive index layers. The high-refractive index layers and low-refractive index layers may be dielectric layers with different refractive indices. In other words, the high or low refractive index is not determined by an absolute value, but refers to the relative high or low refractive index of adjacent layers when laminated.

[0016] By stacking high-refractive index layers and low-refractive index layers with different refractive indices, reflection of visible light is suppressed. Furthermore, from the viewpoint of relatively easily fabricating an anti-reflection film with low visible light reflectance, the outermost layer of the stacked high-refractive index layers and low-refractive index layers is the low-refractive index layer 11. In this specification, visible light reflectance means the reflectance of light with a wavelength of 550 nm.

[0017] Furthermore, by reducing the thickness of the low-refractive-index layers 12 and 13 located in the third and fifth layers from the outermost layer, it is possible to suppress the reflectance of not only visible light but also infrared light. The low-refractive-index layers 12 and 13 located in the third and fifth layers from the outermost layer correspond to the second and third low-refractive-index layers, respectively, when only low-refractive-index layers are considered, with the outermost low-refractive-index layer being the first. In this specification, infrared light reflectance refers to the reflectance of light with a wavelength of 950 nm.

[0018] The specific thickness of the low refractive index layer 12, which is the third layer from the outermost layer, is 35 nm or less. The thickness of the low refractive index layer 13, which is the fifth layer from the outermost layer, is 15 nm or less. This significantly reduces the reflectance of infrared light, and increases the transmittance of infrared light. This reduces loss of sensing light and signal light from the infrared sensor, suppressing malfunctions and errors in the sensor.

[0019] The thickness of the low refractive index layer 12 located in the third from the outermost layer may be 35 nm or less, preferably 25 nm or less, and more preferably 15 nm or less. The thickness of the low refractive index layer 13 located in the fifth from the outermost layer may be 15 nm or less, preferably 10 nm or less. Although there is no particular lower limit, the thickness of the low refractive index layers located in the third and fifth from the outermost layers is usually preferably 5 nm or more.

[0020] The thickness of the low refractive index layer 12 located as the third layer from the outermost layer and the thickness of the low refractive index layer 13 located as the fifth layer may be the same or different.

[0021] There are no particular limitations on the thickness of the low refractive index layers other than the low refractive index layers 12 and 13 located as the third and fifth layers from the outermost layers. From the viewpoint of suppressing reflectance, the outermost low refractive index layer 11 is preferably thicker than the third and fifth low refractive index layers 12 and 13, more preferably 75 nm or thicker, still more preferably 80 nm or thicker, and even more preferably 85 nm or thicker. From the viewpoint of designing a display device, the thickness of the outermost low refractive index layer 11 is preferably 110 nm or thicker, and more preferably 100 nm or thicker.

[0022] The thickness of the high-refractive index layer in the anti-reflection coating is not particularly limited. When the cover glass with the anti-reflection coating is used in a display device, the high-refractive index layer 21 located second from the outermost layer, i.e., the high-refractive index layer located outermost among the high-refractive index layers, is preferably 40 nm or less, more preferably 35 nm or less, and even more preferably 30 nm or less, in terms of the design of the device. Furthermore, from the viewpoint of reducing reflectance, the high-refractive index layer 21 located second is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more.

[0023] The thickness of the fourth to the outermost high refractive index layers in the antireflection coating 1 is preferably 2 nm or more, more preferably 3 nm or more, and even more preferably 4 nm or more, from the viewpoint of reducing reflectance. From the viewpoint of productivity, the thickness of the fourth to the outermost high refractive index layers is preferably 25 nm or less, more preferably 20 nm or less, and even more preferably 15 nm or less.

[0024] The total number of high refractive index layers and low refractive index layers constituting the antireflection film 1 may be 5 or more, but from the viewpoint of reflectance, it is preferably 8 or more, more preferably 10 or more. From the viewpoint of productivity, the total number of layers is preferably 12 or less, more preferably 11 or less.

[0025] The layer of the anti-reflection film that contacts the cover glass may be either a low-refractive index layer or a high-refractive index layer, but a low-refractive index layer is preferred from the viewpoint of adhesion. In Fig. 3, a dotted line "..." is shown between the high-refractive index layer 23, which is the sixth layer from the outermost layer, and the low-refractive index layer 14, which contacts the cover glass. This dotted line indicates that any number of low-refractive index layers and high-refractive index layers may be alternately stacked between the high-refractive index layer 23, which is the sixth layer from the outermost layer, and the low-refractive index layer 14, which contacts the cover glass.

[0026] The total thickness of the high refractive index layer and the low refractive index layer, ie, the thickness of the antireflection film 1, is not particularly limited, but from the viewpoint of productivity, it is preferably 550 nm or less, more preferably 350 nm or less, and even more preferably 290 nm or less.

[0027] The refractive index of the high refractive index layer at a wavelength of 550 nm is preferably 1.9 or more, more preferably 2.2 or more, from the viewpoint of reducing reflectance. There is no particular upper limit to the refractive index, but it is usually 2.5 or less.

[0028] The refractive index of the low refractive index layer at a wavelength of 550 nm is preferably 1.6 or less, more preferably 1.5 or less, from the viewpoint of reducing reflectance. The lower limit of the refractive index is not particularly limited, but is usually 1.35 or more.

[0029] The high refractive index layer and the low refractive index layer are preferably composed of one or more oxides, nitrides, or fluorides selected from the group consisting of Mo, W, Mg, Si, Nb, Ti, Zr, Ta, Al, Sn, and In. The use of the above oxides, nitrides or fluorides is preferred because it reduces the absorption ability of the high refractive index layer and the low refractive index layer over the entire visible wavelength range and also reduces the reflectance of visible light and infrared light.

[0030] The materials constituting the high-refractive index layer and the low-refractive index layer are appropriately selected from the above oxides, nitrides, or fluorides to achieve the desired refractive index. Each of the high-refractive index layer and the low-refractive index layer may be composed of only one of the above oxides, nitrides, and fluorides, or two or more of them. Furthermore, when there are multiple high-refractive index layers and multiple low-refractive index layers, they may be composed of the same material or different materials. In other words, the multiple high-refractive index layers and multiple low-refractive index layers may have different refractive indices.

[0031] Among the above, the high refractive index material constituting the high refractive index layer is preferably an oxide of at least one selected from the group consisting of Mo, W, Mg, Si, Nb, Ti, Zr, Ta, Al, Sn, and In.

[0032] Among the above, the low refractive index material constituting the low refractive index layer is preferably at least one selected from the group consisting of SiO2, MgF2, a material containing a mixed oxide of Si and Sn, a material containing a mixed oxide of Si and Zr, and a material containing a mixed oxide of Si and Al, more preferably SiO2, and even more preferably containing mainly SiO2. Note that, in this specification, "containing mainly" means that the material accounts for 20 mass% or more of the components constituting the layer.

[0033] The anti-reflection coating may be formed directly on the surface of the cover glass, or may be formed on the surface of a film, which is then attached to the cover glass to form the anti-reflection coating on the surface of the cover glass. The film is not particularly limited as long as it is transparent, and for example, what is generally called a clear hard coat (CHC) film can be used.

[0034] When forming an anti-reflection coating on the surface of the film, a silicon nitride (SiN) layer may be formed on the surface of the film to prevent gas components from escaping from the film, and then the anti-reflection coating may be formed. The thickness of such a layer is not particularly limited, but may be, for example, 5 to 30 nm.

[0035] The adhesive layer used to attach the film to the cover glass is not particularly limited, but for example, an acrylic optical adhesive, a silicone adhesive, a urethane adhesive, etc. can be used. The adhesive layer is used to attach the film so that it is positioned on the cover glass side, i.e., so that the anti-reflection film is on the outside. The thickness of the adhesive layer is not particularly limited, but for example, it can be 5 to 100 μm.

[0036] Such an anti-reflection coating may be formed on both surfaces of the cover glass via a film, or an anti-reflection coating may be formed directly on one surface of the cover glass and an anti-reflection coating may be formed on the other surface via a film.

[0037] Alternatively, the anti-reflection film may be formed on an IR (infrared) transmitting ink applied to the surface of the cover glass or film. IR transmitting ink is preferred for improving design. Conventional known IR transmitting inks can be used.

[0038] When a cover glass with an anti-reflection coating is used in a display device, the visible light reflectance at a wavelength of 550 nm of the anti-reflection coating is preferably 1% or less, more preferably 0.4% or less, and even more preferably 0.3% or less, from the viewpoint of visibility of the display device. The lower the visible light reflectance, the better, but it is usually 0.05% or more. In this specification, the visible light reflectance at a wavelength of 550 nm and the infrared light reflectance at a wavelength of 950 nm are values ​​measured using a spectrophotometer (manufactured by Shimadzu Corporation, product name: SolidSpec-3700). The visible light transmittance at a wavelength of 550 nm and the infrared light transmittance at a wavelength of 950 nm, which will be described later, are both normal incidence transmittances, and are also values ​​measured using a spectrophotometer (manufactured by Shimadzu Corporation, product name: SolidSpec-3700).

[0039] The infrared light reflectance of the anti-reflection coating at a wavelength of 950 nm is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less, from the viewpoint of preventing malfunction of an infrared sensor when the cover glass with the anti-reflection coating is used together with the infrared sensor. The lower the infrared light reflectance, the better, but it is usually 0.5% or more.

[0040] The color of the cover glass with anti-reflection coating can be determined based on the color index. The color index is determined from the reflection spectrum of the spectral reflectance obtained during the reflectance measurement, and is a color index specified in JIS Z 8729:2004. * value and b * This is the value that is sought.

[0041] The antireflection coating can be formed on the main surface of the cover glass by a known film formation method such as sputtering, ion beam sputtering, vacuum deposition, ion-assisted deposition using plasma, ion plating, etc. That is, the high refractive index layer and the low refractive index layer that make up the antireflection coating are formed on the main surface of the cover glass in the appropriate lamination order. Examples of sputtering methods include magnetron sputtering, pulse sputtering, AC sputtering, and digital sputtering. Among the above methods, magnetron sputtering, for example, is a method in which a magnet is placed on the backside of the material that will become the high-refractive index layer or the low-refractive index layer to generate a magnetic field, and gas ion atoms collide with the surface of the material and are ejected, thereby forming a sputtering film with a thickness of several nanometers. A continuous film of the oxide or nitride of the metal used as the material can be formed.

[0042] Unlike conventional magnetron sputtering, digital sputtering first forms an ultrathin metal film by sputtering, then oxidizes it by irradiating it with oxygen plasma, oxygen ions, or oxygen radicals. This ultrathin metal film formation and oxidation process is repeated in the same chamber to form a thin film that will become a high-refractive index layer or a low-refractive index layer. In this case, the film-forming molecules are metal when deposited on the substrate, so they are presumably more ductile than films deposited as metal oxides. Therefore, even with the same energy, the film-forming molecules are more likely to rearrange, resulting in a denser, smoother film.

[0043] The anti-reflection film may be formed on at least one of the main surfaces of the cover glass. When the cover glass with the anti-reflection film is used in a display device, the anti-reflection film is preferably formed on the main surface of the cover glass that is exposed to the outside. If necessary, the anti-reflection film may be formed on both main surfaces of the cover glass. The surface side of the cover glass exposed to the outside means the surface side opposite to the surface side on which the infrared sensor and the display unit of the display device are located.

[0044] [Cover glass] The cover glass provided with the anti-reflection coating preferably has a refractive index of 1.4 or more and 1.7 or less, because when the cover glass with the anti-reflection coating is used in a display device, reflection at the bonding surface can be sufficiently suppressed when optically bonding a display, touch panel, etc. Glasses with various compositions can be used for the cover glass. For example, those containing sodium are preferred, and compositions that can be strengthened by molding or chemical strengthening are more preferred. Other examples include aluminosilicate glass, soda-lime glass, borosilicate glass, lead glass, alkali-barium glass, and aluminoborosilicate glass.

[0045] The thickness of the cover glass is not particularly limited, but in order to effectively perform chemical strengthening treatment, it is usually preferably 5 mm or less, more preferably 3 mm or less. The lower limit is not particularly limited, but from the viewpoint of strength, it is preferably 0.5 mm or more. In addition, it is preferable to use chemically strengthened glass in order to increase strength.

[0046] When the cover glass with anti-reflection coating is used together with an infrared sensor, the infrared light transmittance at a wavelength of 950 nm is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more, with the higher the better, from the viewpoint of preventing malfunction of the infrared sensor.

[0047] The visible light transmittance at a wavelength of 550 nm of the cover glass with anti-reflection film is preferably 90% or more, more preferably 92% or more, and the higher the better.

[0048] When the cover glass is subjected to an anti-glare treatment, the chemical strengthening treatment is preferably carried out after the anti-glare treatment and before the anti-reflection film is formed.

[0049] The anti-glare treatment is preferably applied to the main surface of the cover glass on the side having the anti-reflection film. The antiglare treatment method is not particularly limited, and a method of performing a surface treatment on the main surface of the glass to form the desired unevenness can be used. Specifically, a method of performing a chemical treatment on the main surface of the cover glass, such as a frost treatment, can be used. In the frost treatment, for example, the cover glass, which is the object to be treated, is immersed in a mixed solution of hydrogen fluoride and ammonium fluoride, and the immersion surface can be chemically surface treated. In addition to chemical treatment methods, physical treatment methods such as sandblasting, in which crystalline silicon dioxide powder, silicon carbide powder, or the like is sprayed onto the surface of the glass substrate using pressurized air, or polishing with a brush moistened with water and coated with crystalline silicon dioxide powder, silicon carbide powder, or the like, can also be used.

[0050] <Display device> As shown in Fig. 2, the cover glass with anti-reflection film according to this embodiment is preferably used together with an infrared sensor 4. Furthermore, a display device 10 according to this embodiment includes the infrared sensor 4 and a cover glass 2 provided with an anti-reflection film 1. The cover glass 2 provided with the anti-reflection film 1 here can be the same as the cover glass with anti-reflection film described above in <Cover glass with anti-reflection film>, and the preferred aspects are also the same. The infrared sensor 4 is not particularly limited as long as it includes a light source that emits sensing light and a camera that detects signal light obtained through monitoring, etc. When a cover glass with an anti-reflection coating is used together with an infrared sensor, there is no need to provide an opening as shown in Fig. 1 at the location where the light entering and leaving the infrared sensor passes, due to the high infrared light transmittance of the cover glass with an anti-reflection coating. In other words, from the standpoints of design and cost, it is preferable that the cover glass with an anti-reflection coating does not include the opening. A printed layer 5 may be formed between the infrared sensor 4 and the cover glass 2. The printed layer 5 may be a concealing layer that conceals wiring members and the like that are arranged on the periphery of the cover glass 2, or may be a decorative layer that enhances the design of the display device 10. When a printed layer or decorative layer is present, it is preferable not to provide a printed layer 5 in the light-transmitting region in order to maintain the transmittance of infrared light in the light-transmitting region, which is the incoming and outgoing light of the infrared sensor. Alternatively, it is preferable to provide an IR-transmitting ink layer 6 instead of the printed layer 5. The IR-transmitting ink layer is a layer formed using ink with high transmittance of infrared light, and is preferably formed in the region through which the sensing light and signal light of the infrared sensor, i.e., the incoming and outgoing light, pass.

[0051] The display panel in the display device is not particularly limited. Examples include a liquid crystal panel, an organic EL panel, a plasma display panel, an electronic ink panel, etc. Depending on the type of display panel, the display device may further include a backlight unit. In addition, other conventionally known devices such as a touch panel may also be provided.

[0052] In order to protect the outermost surface of the anti-reflection film, a display device may further have an anti-fouling film (AFP film: Anti Finger Print film) formed on the surface of the anti-reflection film. When forming the anti-fouling film, it is preferable that the low refractive index layer that is the outermost layer of the anti-reflection film is a layer that mainly contains SiO2, from the viewpoint of bonding properties related to durability.

[0053] Since the anti-fouling film is laminated on the anti-reflection film, when an anti-reflection film is formed on both main surfaces of the cover glass, an anti-fouling film can be formed on the surface of both anti-reflection films. On the other hand, the anti-fouling film only needs to be provided in a location where there is a possibility of contact with a human hand, etc. Therefore, it is sufficient that the anti-fouling film is formed at least on the surface of the anti-reflection film located on the outermost layer side of the display device.

[0054] The antifouling film can be composed of, for example, a fluorine-containing organosilicon compound. The fluorine-containing organosilicon compound can be any compound that can impart antifouling, water repellency, and oil repellency. For example, a fluorine-containing organosilicon compound having one or more groups selected from the group consisting of a polyfluoropolyether group, a polyfluoroalkylene group, and a polyfluoroalkyl group can be used. The polyfluoropolyether group is a divalent group having a structure in which polyfluoroalkylene groups and etheric oxygen atoms are alternately bonded.

[0055] Alternatively, commercially available fluorine-containing organosilicon compounds having one or more groups selected from the group consisting of polyfluoropolyether groups, polyfluoroalkylene groups, and polyfluoroalkyl groups may be used. Specifically, KP-801 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), KY178 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), KY-130 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), KY-185 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), Optool (registered trademark) DSX, and Optool AES (all trade names, manufactured by Daikin Corporation) are preferably used.

[0056] The display device according to this embodiment is suitable for in-vehicle information devices such as navigation systems and audio equipment, mobile communication devices, signage, and the like. [Example]

[0057] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. Examples 1 to 3 are working examples, and Example 4 is a comparative example.

[0058] (Example 1) A chemically strengthened glass plate (DRAGONTRAIL (registered trademark) manufactured by AGC) measuring 50 mm x 50 mm x 2 mm was used as the cover glass. Using TiO2 as a high-refractive index material and SiO2 as a low-refractive index material, they were laminated in that order on one main surface of the cover glass by magnetron sputtering, resulting in a cover glass with an anti-reflection coating in which TiO2 layers as high-refractive index layers and SiO2 layers as low-refractive index layers were laminated alternately. The anti-reflection film was an eight-layer laminate film with the outermost layer being a low refractive index layer, and the thicknesses of the layers, from the outermost layer, were 97 nm (low refractive index layer), 28 nm (high refractive index layer), 16 nm (low refractive index layer), 81 nm (high refractive index layer), 10 nm (low refractive index layer), 41 nm (high refractive index layer), 36 nm (low refractive index layer), and 6 nm (high refractive index layer).

[0059] (Example 2) A cover glass with an anti-reflection film was obtained in the same manner as in Example 1, except that the number of high refractive index layers and low refractive index layers in the anti-reflection film and the thickness of each layer were changed as follows. The anti-reflection film was a 12-layer laminate film with the outermost layer being a low refractive index layer, and the thicknesses of the layers, from the outermost layer, were 93.3 nm (low refractive index layer), 26 nm (high refractive index layer), 10 nm (low refractive index layer), 75.3 nm (high refractive index layer), 8 nm (low refractive index layer), 32.3 nm (high refractive index layer), 25.9 nm (low refractive index layer), and 17.5 nm (high refractive index layer).

[0060] (Example 3) A 15-nm-thick layer of silicon nitride (SiN) was deposited on the surface of a clear hard coat (CHC) film (manufactured by Toppan TOMOEGAWA Optical Films Co., Ltd.). Next, TiO2 as a high-refractive index material and SiO2 as a low-refractive index material were laminated in order on a layer of silicon nitride (SiN) by magnetron sputtering. This resulted in a CHC film with an anti-reflection coating, in which high-refractive index TiO2 layers and low-refractive index SiO2 layers were alternately laminated. This was then bonded to a 50mm x 50mm x 2mm chemically strengthened glass plate (AGC Dragon Trail (registered trademark)) via a 25μm thick adhesive layer (Tomoegawa Paper Co., Ltd., TD06A) so that the CHC film faced the chemically strengthened glass plate. The antireflection coating was an eight-layer laminate with the outermost layer being a low-refractive index layer, and the thicknesses of the layers, from the outermost layer, were 98 nm (low-refractive index layer), 29 nm (high-refractive index layer), 16 nm (low-refractive index layer), 87 nm (high-refractive index layer), 11 nm (low-refractive index layer), 44 nm (high-refractive index layer), 34 nm (low-refractive index layer), and 10 nm (high-refractive index layer). A 4 nm antifouling coating (KY-185, manufactured by Shin-Etsu Chemical Co., Ltd.) was further deposited on the surface of the antireflection coating.

[0061] (Example 4) A cover glass with an anti-reflection film was obtained in the same manner as in Example 1, except that the number of high refractive index layers and low refractive index layers in the anti-reflection film and the thickness of each layer were changed as follows. The anti-reflection film was a five-layer laminate film with the outermost layer being a low refractive index layer, and the thicknesses of the layers, from the outermost layer, were 80 nm (low refractive index layer), 122 nm (high refractive index layer), 36 nm (low refractive index layer), 6 nm (high refractive index layer), and 16 nm (low refractive index layer).

[0062] (evaluation) The visible light reflectance and infrared light reflectance of the anti-reflection coating, and the visible light transmittance and infrared light transmittance of the cover glass with the anti-reflection coating were measured using a spectrophotometer (Shimadzu SolidSpec-3700). The visible light reflectance and infrared light reflectance were measured at wavelengths of 550 nm and 950 nm, respectively. The visible light transmittance and infrared light transmittance were measured at wavelengths of 550 nm and 950 nm, respectively, and the normal transmittance was calculated. The results are shown in Table 1.

[0063] From the reflectance spectrum obtained by measurement using the above spectrophotometer, the color index a * Value and color index b * The values ​​were calculated and the results are shown in Table 1.

[0064] [Table 1]

[0065] From the above results, it was found that the anti-reflection film formed on the cover glass had a low refractive index layer as its outermost layer, and that by further reducing the thicknesses of the third and fifth low refractive index layers from the outermost layer, a significant reduction in infrared light reflectance was achieved.

[0066] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2020-211763) filed on December 21, 2020, the contents of which are incorporated herein by reference. [Industrial Applicability]

[0067] When used in a display device equipped with an infrared sensor, the cover glass with an anti-reflection film according to the present invention can achieve good visibility and high infrared light transmittance without opening a portion of the cover glass. Furthermore, from a design perspective, this prevents loss of design aesthetics and also reduces the cost increase associated with drilling. Therefore, this glass achieves both high design aesthetics and suppresses malfunction of the infrared sensor, making it useful for display device applications, more specifically, for applications such as in-vehicle information devices such as navigation systems and audio equipment, mobile communication devices, and signage. [Explanation of symbols]

[0068] 1: Anti-reflection film 2: Cover glass 3: Display section 4: Infrared sensor 5: Printing layer 6: IR transparent ink printing layer 10: Display device 11: Low refractive index layer located on the outermost layer 12: Low refractive index layer located third from the outermost layer 13: Low refractive index layer located fifth from the outermost layer 14: Low refractive index layer in contact with the cover glass 21: High refractive index layer located second from the outermost layer 22: High refractive index layer located fourth from the outermost layer 23: High refractive index layer located in the sixth layer from the outermost layer

Claims

1. A cover glass provided with an anti-reflective coating, the antireflection film is formed by alternately laminating high-refractive index layers and low-refractive index layers, the outermost layer of which is a low-refractive index layer; the total number of the high refractive index layers and the low refractive index layers is 5 to 12; the total thickness of the high refractive index layer and the low refractive index layer is 350 nm or less; the thickness of the low refractive index layer located third from the outermost layer is 35 nm or less, and the thickness of the low refractive index layer located fifth from the outermost layer is 10 nm or less; The infrared light reflectance at a wavelength of 950 nm is 5% or less, the high refractive index material constituting the high refractive index layer is an oxide of at least one element selected from the group consisting of Mo, W, Mg, Si, Nb, Ti, Zr, Ta, Al, Sn, and In; The cover glass with an anti-reflection film is characterized in that the low refractive index material constituting the low refractive index layer is at least one selected from the group consisting of SiO 2 , MgF 2 , a material containing a mixed oxide of Si and Sn, a material containing a mixed oxide of Si and Zr, and a material containing a mixed oxide of Si and Al.

2. 2. The cover glass with an anti-reflection coating according to claim 1, wherein the anti-reflection coating has a visible light reflectance of 0.4% or less at a wavelength of 550 nm.

3. 3. The cover glass with anti-reflection coating according to claim 1, wherein the high refractive index layer has a refractive index of 1.9 or more at a wavelength of 550 nm, and the low refractive index layer has a refractive index of 1.6 or less at a wavelength of 550 nm.

4. 4. The cover glass with anti-reflection coating according to claim 1, which is used together with an infrared sensor and has no opening at a location through which light entering and leaving the infrared sensor passes.

5. A display device comprising an infrared sensor and the cover glass with anti-reflection film according to any one of claims 1 to 4.

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