JP2018058738A - Cover glass for display device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cover glass for a display device, which has an antireflection film, has high transmittance of near infrared light, and has also excellent scratch resistance.SOLUTION: A cover glass for a display device has a transparent substrate and an antireflection film arranged on the transparent substrate. The antireflection film is configured such that high refractive index films with refractive index of 1.9 or more and low refractive index films with refractive index of 1.6 or less are alternately stacked. Each of the high refractive index film and the low refractive index film is composed of a material including at least one selected from an oxide, a nitride, and an oxynitride of Al, Zr, Ti, Si, Sn, Hf and Ta. The cover glass for a display device has visible ray reflectance of 1.5% or less, and has a region where transmittance gets to be 90% or more in a continuous wavelength range of at least 10 nm in a wavelength range of 800-1,200 nm.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a cover glass for a display device and an electronic apparatus.

  Conventionally, a cover glass is provided on the front surface in order to protect and strengthen the display device. Such a cover glass is provided with an antireflection film for preventing reflection of light in order to improve display visibility (see, for example, Patent Document 1).

  By the way, in a mobile phone having a touch panel display device, for example, a smartphone, a proximity sensor may be provided around the display device. With the proximity sensor, it is possible to detect that a human ear or the like is close to the mobile phone, and it is possible to know whether or not the telephone is in a call state. Thereby, for example, the operation can be invalidated to prevent a malfunction during a call, or the operation can be turned off to suppress the power consumption of the battery.

  The proximity sensor includes, for example, a light emitting unit that emits near infrared light, and a light receiving unit that receives the near infrared light emitted from the light emitting unit and reflected by the detection target. The light emitting unit and the light receiving unit are provided, for example, on the display surface side of the mobile phone.

  When in a call state, that is, when a human ear or the like is in proximity to the proximity sensor, the near infrared light emitted from the light emitting unit is reflected by the human ear or the like that is the detection target, and the reflected near Infrared light is received by the light receiving unit. Thereby, it can detect that it is in a telephone call state (for example, refer patent documents 2 and 3).

Japanese Patent Laid-Open No. 2006-102757 JP, 2006-103856, A Japanese Patent Laid-Open No. 2006-086068

  However, in the conventional antireflection film, only the reflection in the visible region is considered, and the reflection in the near infrared region is not necessarily considered. Usually, the reflectance is sufficiently low in the visible region, but the reflectance increases in the near infrared region as the wavelength increases. For this reason, near-infrared light used for the proximity sensor is not sufficiently transmitted, and there is a possibility that the detection object cannot be detected appropriately. Further, from the viewpoint of use in a touch panel type display device or the like, the antireflection film is also required to have excellent scratch resistance.

  The problem to be solved by the present invention is to provide a cover glass for a display device having an antireflection film and having a high transmittance of near infrared light. Another object of the present invention is to provide a display device having such a cover glass for a display device.

The cover glass for a display device of the present invention is a cover glass for a display device having a transparent base material and an antireflection film provided on the transparent base material, and the antireflection film has a refractive index of 1. A high refractive index film having a refractive index of 9 or more and a low refractive index film having a refractive index of 1.6 or less are alternately laminated, and the high refractive index film and the low refractive index film are respectively It is made of a material containing at least one selected from oxides, nitrides, and oxynitrides of Al, Zr, Ti, Si, Sn, Hf, and Ta, and has a visible light reflectance of 1.5% or less, 800 to 1200 nm. In the continuous wavelength range of at least 10 nm of the wavelength range, the transmittance is 90% or more.

  According to the present invention, a cover glass for a display device having an antireflection film and having a high transmittance of near infrared light is provided.

It is sectional drawing which shows the cover glass for display apparatuses of embodiment. It is a figure explaining a radical assist sputtering device. It is a top view which shows the electronic device of embodiment. It is the sectional view on the AA line of the electronic device shown in FIG.

Hereinafter, modes for carrying out the present invention will be described.
FIG. 1 is a cross-sectional view showing an embodiment of a cover glass for a display device.
In the following description, the display device cover glass is simply referred to as a cover glass.

  The cover glass 10 includes a transparent base material 11 and an antireflection film 12 provided on the transparent base material 11. The antireflection film 12 has a structure in which a high refractive index film 13 having a refractive index of 1.9 or more and a low refractive index film 14 having a refractive index of 1.6 or less are alternately stacked. The refractive index is a refractive index at a wavelength of 600 nm.

  The cover glass 10 has a visible light reflectance of 1.5% or less and a region where the transmittance is 90% or more in a continuous wavelength range of at least 10 nm in a wavelength range of 800 to 1200 nm. The visible light reflectance is a visible light reflectance defined in JIS R 3106 (1998). Further, the high refractive index film 13 and the low refractive index film 14 constituting the antireflection film 12 are selected from oxides, nitrides, or oxynitrides of Al, Zr, Ti, Si, Sn, Hf, Ta, respectively. It is made of a material containing at least one kind.

  By having a visible light reflectance of 1.5% or less, reflection of visible light is suppressed, and display visibility when arranged on the front surface of the display device is improved. Moreover, by having a region where the transmittance is 90% or more in a continuous wavelength range of at least 10 nm in the wavelength range of 800 to 1200 nm, the transmission of near-infrared light becomes good and the use of a proximity sensor becomes possible.

  Hereinafter, the structural member of the cover glass 10 is demonstrated concretely.

  The transparent substrate 11 only needs to be transparent to visible light and near-infrared light, and may be either inorganic glass or organic glass.

  Examples of the inorganic glass include soda lime glass, alkali-free glass, borosilicate glass, aluminosilicate glass, and sapphire glass. As the inorganic glass, tempered glass or sapphire glass subjected to physical strengthening or chemical strengthening is preferable because of its high strength and excellent scratch resistance. The inorganic glass may be hard-coated.

  In the physical strengthening, the surface of the glass heated to the vicinity of the softening point is rapidly cooled by air cooling or the like. By rapid cooling, a compressive stress layer is formed on the surface of the glass to improve the strength.

  In chemical strengthening, alkali metal ions (typically Li ions and Na ions) having a small ionic radius on the surface of the glass are exchanged with ions having a larger ionic radius (typically K) by ion exchange at a temperature below the glass transition point. Ion). By such ion exchange, a compressive stress layer is formed on the surface of the glass and the strength is improved. Chemical strengthening is usually performed by immersing glass in a molten salt containing an alkali metal.

  Examples of the organic glass include polycarbonate, polyester, triacetyl cellulose, cycloolefin polymer, polymethyl methacrylate, and the like. From the viewpoint of weather resistance and transparency, polycarbonate, polyester, and cycloolefin polymer are preferable. Examples of the polyester include polyethylene terephthalate and polyethylene naphthalate.

  The form of the transparent substrate 11 can be appropriately selected according to the display device, and may be either plate-like or film-like. The thickness can also be appropriately selected according to the display device. From the viewpoint of ensuring strength and the like, 0.1 mm or more is preferable, and 0.3 mm or more is more preferable. Moreover, from a viewpoint of thickness reduction and weight reduction, 2 mm or less is preferable and 1.5 mm or less is more preferable.

  As described above, the antireflection film 12 is formed by alternately laminating a high refractive index film 13 having a refractive index of 1.9 or more and a low refractive index film 14 having a refractive index of 1.6 or less. It is.

  The stacking order of the high refractive index film 13 and the low refractive index film 14 is not particularly limited. For example, the film disposed on the transparent substrate 11 side may be the high refractive index film 13 or the low refractive index film 14. Moreover, the film | membrane arrange | positioned on the opposite side to the transparent base material 11 side may be the high refractive index film | membrane 13, and the low refractive index film | membrane 14 may be sufficient, but a low-refractive-index material is preferable from a viewpoint of reducing a reflectance. In the example of FIG. 1, the film closest to the transparent substrate 11 is a high refractive index film 13, and the film farthest from the transparent substrate 11 is a low refractive index film 14. Further, the high refractive index film 13 is partially laminated adjacently, or the low refractive index film 14 is partially laminated adjacently, that is, even if not alternately laminated. Acceptable if any.

  The number of layers of the high refractive index film 13 is preferably two or more in the antireflection film 12, and more preferably three or more. As the number of layers of the high refractive index film 13 increases, the reflection of visible light is suppressed and the transmission of near-infrared light is also improved. Usually, the number of layers of the high refractive index film 13 is preferably 10 layers or less, more preferably 8 layers or less from the viewpoint of productivity and the like.

  The number of layers of the low refractive index film 14 is preferably two or more in the antireflection film 12 and more preferably three or more. As the number of layers of the low refractive index film 14 increases, the reflection of visible light is suppressed and the transmission of near-infrared light is also improved. Usually, the number of layers of the low refractive index film 14 is preferably 10 layers or less, more preferably 8 layers or less from the viewpoint of productivity and the like.

  The number of layers of the antireflection film 12, that is, the total number of layers of all the high refractive index films 13 and the low refractive index films 14 suppresses the reflection of visible light and improves the transmission of near infrared light. Therefore, 4 layers or more are preferable, and 6 layers or more are more preferable. Usually, the number of layers of the antireflection film 12 is preferably 20 layers or less, more preferably 18 layers or less, from the viewpoint of productivity and the like.

  The thickness of each layer of the antireflection film 12, the high refractive index film 13, and the low refractive index film 14 is adjusted so that the cover glass 10 has predetermined optical characteristics. Specifically, a region where the visible light reflectance is 1.5% or less and the transmittance is 90% or more in a continuous wavelength range of at least 10 nm in the wavelength range of 800 to 1200 nm is formed. Adjusted to In addition, the thickness of the antireflection film 12, the high refractive index film 13, and the low refractive index film 14 is a geometric thickness.

  The thickness of the antireflection film 12, that is, the total thickness of all the layers of the high refractive index film 13 and all the layers of the low refractive index film 14 suppresses reflection of visible light and provides good transmission of near infrared light. Therefore, 300 nm or more is preferable, 330 nm or more is more preferable, and 350 nm or more is more preferable. In particular, 550 nm or more is preferable and 600 nm or more is more preferable because transmission of near infrared light becomes good. On the other hand, from the viewpoint of productivity and the like, 1000 nm or less is preferable, 900 nm or less is more preferable, and 800 nm or less is more preferable.

  The thickness of each layer of the high refractive index film 13 is preferably 1 nm or more, and more preferably 3 nm or more, since reflection of visible light is suppressed and transmission of near-infrared light is improved. In particular, the thickness of one high refractive index film 13 is 1 nm or more and less than 10 nm, and the thicknesses of all the high refractive index films 13 other than the one high refractive index film 13 are 10 nm or more, or all The thickness of each layer of the high refractive index film 13 is preferably 10 nm or more. On the other hand, from the viewpoint of productivity and the like, the thickness of each layer of the high refractive index film 13 is preferably 250 nm or less, and more preferably 200 nm or less.

  The thickness of each layer of the low refractive index film 14 is preferably 1 nm or more, more preferably 3 nm or more, since reflection of visible light is suppressed and transmission of near-infrared light is improved. In particular, the thickness of one layer of the low refractive index film 14 is 1 nm or more and less than 10 nm, and the thicknesses of all the layers of the low refractive index film 14 other than the one layer of low refractive index film 14 are 10 nm or more, or all The thickness of each layer of the low refractive index film 14 is preferably 10 nm or more. On the other hand, from the viewpoint of productivity and the like, the thickness of each layer of the low refractive index film 14 is preferably 300 nm or less, and more preferably 250 nm or less.

  The total thickness of all the layers of the high refractive index film 13 is preferably 100 nm or more, and more preferably 150 nm or more, since reflection of visible light is suppressed and near-infrared light transmission is improved. On the other hand, from the viewpoint of productivity and the like, 500 nm or less is preferable, and 450 nm or less is more preferable.

  The total thickness of all the layers of the low refractive index film 14 is preferably 100 nm or more, and more preferably 150 nm or more, since reflection of visible light is suppressed and transmission of near infrared light is improved. On the other hand, from the viewpoint of productivity and the like, 500 nm or less is preferable, and 450 nm or less is more preferable.

  The average thickness of all the layers of the high refractive index film 13 is preferably 30 nm or more, more preferably 35 nm or more, and more preferably 40 nm or more because reflection of visible light is suppressed and transmission of near infrared light is improved. Is more preferable, and 43 nm or more is particularly preferable. On the other hand, from the viewpoint of productivity and the like, 60 nm or less is preferable, and 55 nm or less is more preferable.

  The average thickness of all the layers of the low refractive index film 14 is preferably 25 nm or more, and more preferably 30 nm or more, since reflection of visible light is suppressed and transmission of near infrared light is improved. On the other hand, from the viewpoint of productivity and the like, 100 nm or less is preferable, and 90 nm or less is more preferable.

  The antireflective film 12 has a high refractive index film 13 when the high refractive index film 13 and the low refractive index film 14 adjacent to the opposite side of the transparent base material 11 are formed as a single unit. It is preferable to have at least one laminated unit in which the ratio (H / L) of the thickness (H [nm]) to the thickness (L [nm]) of the low refractive index film 14 is 2.0 or more.

  By including at least one laminated unit having a ratio (H / L) of 2.0 or more, reflection of visible light is suppressed and near-infrared light transmission is improved. Such a laminate unit preferably has a ratio (H / L) of 3.0 or more, and more preferably has a ratio (H / L) of 3.5 or more. Usually, the ratio (H / L) in such a laminated unit is preferably 50 or less, and more preferably 40 or less.

  It is preferable that two or more laminated units having a ratio (H / L) of 2.0 or more are provided in the antireflection film 12. By providing two or more stacked units having a ratio (H / L) of 2.0 or more, particularly, reflection of visible light is suppressed and near-infrared light transmission is improved.

  In addition, the lamination | stacking unit provided two or more of these may be arrange | positioned continuously and may be arrange | positioned discontinuously. Moreover, these laminated units do not need to have the same ratio (H / L), and can have different ratios (H / L). Furthermore, as for these lamination | stacking units, it is preferable that at least 1 lamination | stacking unit has ratio (H / L) of 5.0 or more, and it is more preferable to have ratio (H / L) of 10.0 or more.

  For other portions, that is, portions composed of laminated units such that the ratio (H / L) is less than 2.0, all the laminated units have a ratio (H / L) of less than 1.0, or 1 It is preferred that one laminate unit has a ratio (H / L) of 1.0 or more and less than 2.0, and the remaining laminate units have a ratio (H / L) of less than 1.0.

  The ratio (H / L) is usually 0.001 or more. For the above portion, that is, the portion composed of the laminated units whose ratio (H / L) is less than 2.0, all the laminated units have a ratio (H / L) of 0.1 or more, It is preferred that the laminate units have a ratio (H / L) of less than 0.1 and the remaining laminate units have a ratio (H / L) of 0.1 or more.

  Each of the high refractive index films 13 is made of a material containing at least one selected from oxides, nitrides, and oxynitrides of Al, Zr, Ti, Si, Sn, Hf, and Ta. Each of the low refractive index films 14 is made of a material containing at least one selected from oxides, nitrides, and oxynitrides of Al, Zr, Ti, Si, Sn, Hf, and Ta. According to the material, a predetermined refractive index can be obtained.

  As a combination of the high refractive index film 13 and the low refractive index film 14, for example, a combination of the high refractive index film 13 made of Si nitride and the low refractive index film 14 made of Si oxide is preferable. According to such a combination, reflection of visible light is suppressed and transmission of near infrared light is improved.

  Next, the optical characteristics of the cover glass 10 will be described.

  As already described, the cover glass 10 has a visible light reflectance of 1.5% or less and a region where the transmittance is 90% or more in a continuous wavelength range of at least 10 nm of the wavelength range of 800 to 1200 nm. Have. Examples of the region include a region including a typical center wavelength of near-infrared light used for a proximity sensor, specifically, 850 nm, 950 nm, and the like. From the viewpoint of use in a display device, combined use of a proximity sensor, etc., the cover glass 10 preferably further has the following optical characteristics.

  The visible light reflectance is preferably 1.3% or less, more preferably 1.0% or less, and even more preferably 0.9% or less. In the above-mentioned region, that is, the region where the transmittance is 90% or more in the wavelength range of 800 to 1200 nm, the wavelength range where the transmittance is 90% or more continuously in the wavelength range of 800 to 1200 nm has a width of 10 nm or more. By having it, the near-infrared light used for a proximity sensor transmits favorably. The transmittance of the region is preferably 91% or more, more preferably 92% or more, still more preferably 93% or more, and particularly preferably 94% or more.

  For light having at least one wavelength of 800 to 1200 nm, the reflectance when the incident angle is 30 degrees is preferably 3% or less. Examples of the wavelength include typical center wavelengths of near-infrared light used for proximity sensors, specifically, 850 nm, 950 nm, and the like. When the reflectance when the incident angle is 30 degrees is 3% or less, the change in reflectance when the incident angle of near-infrared light is changed, that is, the dependence on the incident angle of near-infrared light is reduced. Therefore, it is preferable. The reflectance when the incident angle is 30 degrees is more preferably 2.5% or less.

  For light having at least one wavelength of 800 to 1200 nm, the reflectance when the incident angle is 60 degrees is preferably 25% or less. Examples of the wavelength include typical center wavelengths of near-infrared light used for proximity sensors, specifically, 850 nm, 950 nm, and the like. When the reflectance when the incident angle is 60 degrees is 25% or less, the change in reflectance when the incident angle of near-infrared light changes, that is, the dependence on the incident angle of near-infrared light is reduced. Therefore, it is preferable. The reflectance when the incident angle is 60 degrees is more preferably 20% or less.

It is preferable that the color difference ΔE (L ^* , a ^* , b ^* ) of the reflected light from the D65 light source of the L ^* a ^* b ^* color system normalized by CIE 1976 satisfies the following formula (1). By satisfying the following formula (1), the color tone of the reflected light becomes close to an achromatic color. Thereby, when it arrange | positions in the front surface of a display apparatus, the color tone change of a display is suppressed. The color tone of the reflected light is a value measured without the influence of reflection on the transparent base material 11 side with respect to the antireflection film 12.
√ ((L ^* ) ² + (a ^* ) ² + (b ^* ) ² ) ≦ 5 (1)

  The cover glass 10 can have a film other than the antireflection film 12 as long as the effects of the present invention are not impaired. Examples of such a material include an antifouling film and a protective film. The antifouling film and the protective film are provided on the side opposite to the transparent substrate 11 side with respect to the antireflection film 12.

  The antifouling film can be composed of a fluorine-containing organosilicon compound. The fluorine-containing organosilicon compound is not particularly limited as long as it imparts antifouling properties, water repellency, and oil repellency. For example, a group consisting of a polyfluoropolyether group, a polyfluoroalkylene group, and a polyfluoroalkyl group And fluorine-containing organosilicon compounds having one or more groups selected from The polyfluoropolyether group means a divalent group having a structure in which polyfluoroalkylene groups and etheric oxygen atoms are alternately bonded.

  When a film other than the antireflection film 12 is provided, it is preferable to satisfy predetermined optical characteristics in a state where a film other than the antireflection film 12 is provided. That is, in a state where a film other than the antireflection film 12 is provided, it has a visible light reflectance of 1.5% or less, and a transmittance of 90% in a continuous wavelength range of at least 10 nm in the wavelength range of 800 to 1200 nm. It is preferable to have the above region.

  Such a cover glass 10 is used for various electronic devices having a display device. Examples of such an electronic device include a television receiver, a personal computer, a navigation system, an operation panel, and a portable information terminal. Examples of the portable information terminal include a portable phone such as a smartphone, a portable computer, a portable game machine, an electronic book, a watch having a display device, and the like. Especially as an electronic device, what has a proximity sensor which uses near-infrared light is preferable.

  Next, the manufacturing method of the cover glass 10 is demonstrated.

  The cover glass 10 can be manufactured by alternately forming the high refractive index film 13 and the low refractive index film 14 constituting the antireflection film 12 on the transparent substrate 11. The film formation can be performed by a vapor phase film formation method. Examples of vapor deposition methods include chemical vapor deposition (CVD) and physical vapor deposition (PVD). Examples of chemical vapor deposition (CVD) include thermal CVD, plasma CVD, and laser CVD. Examples of physical vapor deposition (PVD) include vacuum vapor deposition, ion-assisted vapor deposition, ion plating, and sputtering.

  As the film forming apparatus, for example, a radical assist sputtering apparatus is preferably used. In the radical assist sputtering apparatus, a film formation region and a reaction region are separately provided in a single vacuum vessel, and film formation processing and reaction processing can be performed independently. Hereinafter, the radical assist sputtering apparatus will be specifically described.

FIG. 2 shows an example of a radical assist sputtering apparatus.
The radical assist sputtering apparatus 20 includes an apparatus main body 21 and a drum 22 provided therein. The drum 22 holds the transparent substrate 11 and rotates while holding the transparent substrate 11. The space around the drum 22 is divided into a plurality of regions by the wall portion 23.

  The first region (right side in the figure) is a film formation region, and the target 24 is disposed. A power supply 25 is connected to the target 24. An argon gas supply unit 26 that supplies argon gas is connected to the first region.

  The second region (lower side in the figure) is a reaction region, and the radical source 27 is arranged. A matching machine and an RF source 28 are connected to the radical source 27. In addition, an argon gas supply unit 31 that supplies argon gas, a nitrogen gas supply unit 32 that supplies nitrogen gas, and an oxygen gas supply unit 33 that supplies oxygen gas are connected to the second region.

  In such a radical assist sputtering apparatus 20, first, the transparent substrate 11 is held on the drum 22. Thereafter, when the drum 22 rotates, the transparent substrate 11 is conveyed to the first region (right side in the figure). Argon gas is supplied from the argon gas supply unit 26 to the first region. Then, by sputtering the target 24, a film made of the constituent material of the target 24 is formed on the surface of the transparent substrate 11. An example of such a film is a metal film that has not been oxidized or nitrided. By not oxidizing or nitriding, the film forming speed is improved and the film quality is improved because the film formation is performed stably.

  Thereafter, the drum 22 holding the transparent substrate 11 is rotated, whereby the transparent substrate 11 is conveyed to the second region (lower side in the figure). Nitrogen gas, argon gas, and oxygen gas are supplied to the second region from the argon gas supply unit 31, the nitrogen gas supply unit 32, and the oxygen gas supply unit 33 as necessary. And oxidation and nitridation are performed when a plasma contacts the film | membrane provided in the transparent base material 11. FIG. By using plasma, oxidation and nitridation can be performed uniformly and a dense film can be obtained.

Next, an electronic device having the cover glass 10 will be described.
FIG. 3 is a cross-sectional view showing an embodiment of a mobile phone as an electronic apparatus. FIG. 4 is a cross-sectional view of the mobile phone shown in FIG.

  The mobile phone 40 is called a smartphone, for example, and includes a housing 41, a display device 42, and a cover glass 43. The housing 41 has a box shape with one end opened. The display device 42 is, for example, a touch panel type display device, and is accommodated in a housing 41 having a box shape. The device main body includes such a casing 41 and a display device 42 accommodated in the casing 41. The cover glass 43 has the same size as the housing 41 and is provided so as to cover the housing 41 and the display device 42 accommodated therein. As such a cover glass 43, the cover glass 10 mentioned above is used.

  A proximity sensor 45 is further provided inside the housing 41. Specifically, it is provided in a space portion formed by the casing 41, the display device 42, and the cover glass 43, that is, a gap portion.

  The proximity sensor 45 includes, for example, a light emitting unit 451, a light receiving unit 452, and a substrate 453 on which these are mounted. The proximity sensor 45 is disposed so that the light emitting unit 451 and the light receiving unit 452 are on the cover glass 43 side.

  The light emitting unit 451 emits near infrared light. Specifically, light having a center wavelength in the wavelength range of 800 to 1200 nm is emitted. The light emitting unit 451 may be anything that emits near-infrared light by supplying current, and includes, for example, a near-infrared LED (Light Emitting Diode).

  The light receiving unit 452 receives near infrared light reflected by the detection target. The light receiving unit 452 only needs to receive near-infrared light and generate a current, and examples thereof include a photodiode having a PN junction.

  According to such a portable telephone 40, by having the proximity sensor 45, it is possible to detect whether or not it is in a call state. That is, when in a call state, near-infrared light emitted from the light emitting unit 451 is reflected by a human ear or the like that is a detection target. By receiving the reflected near-infrared light at the light receiving unit 452, it is possible to detect whether or not the telephone is in a call state.

  In particular, by having the above-described cover glass 10 as the cover glass 43, the proximity sensor 45 can appropriately detect. That is, transmission of near-infrared light used for the proximity sensor 45 is not hindered, and detection can be performed appropriately. Moreover, by having the cover glass 10, reflection of visible light is suppressed and it is excellent in display visibility.

  Hereinafter, the present invention will be described more specifically with reference to examples.

<Examples 1-5>
On a chemically tempered glass as a transparent substrate, a silicon nitride film (SiN _x film) as a high refractive index film and a low refractive index film so as to have a film thickness and ratio (H / L) as shown in Table 1 An antireflection film was formed by alternately forming silicon oxide films (SiO ₂ films), and cover glasses of Examples 1 to 5 were manufactured. Hereinafter, the transparent substrate and the antireflection film will be specifically described.

(Transparent substrate)
Put 9700 g of potassium nitrate, 890 g of potassium carbonate and 400 g of sodium nitrate in a stainless steel (SUS) cup and heat to 450 ° C. with a mantle heater to prepare a molten salt with a potassium carbonate concentration of 6 mol% and a sodium concentration of 10,000 ppm by weight. did.

  An aluminosilicate glass (specific gravity 2.48) of 100 mm × 100 mm × 0.56 mm was preheated to 200 to 400 ° C. and then immersed in the molten salt for 2 hours for ion exchange treatment. Then, it cooled to near room temperature and washed with water.

The aluminosilicate glass is composed of SiO ₂ 64.4 mol%, Al ₂ O ₃ 8.0 mol%, Na ₂ O 12.5 mol%, K ₂ O 4.0 mol%, MgO 10.5 mol%, CaO 0.1 mol. %, SrO 0.1 mol%, BaO 0.1 mol%, ZrO ₂ 0.5 mol%.

  Next, a 6.0 wt% nitric acid solution was placed in a beaker and adjusted to a temperature of 40 ° C. with a water bath. The glass was immersed in this nitric acid solution for 120 seconds for acid treatment. Thereafter, the glass was washed with water.

  Next, 4.0 wt% sodium hydroxide aqueous solution was placed in a beaker and adjusted to a temperature of 40 ° C. with a water bath. Thereafter, the glass was immersed in an aqueous sodium hydroxide solution for 120 seconds for alkali treatment. Thereafter, the glass was washed with water. Then, it was made to dry by air blow, and the chemically strengthened glass used as a transparent base material was obtained.

(Antireflection film)
An antireflection film was formed by alternately forming a silicon nitride film and a silicon oxide film on the surface of the chemically strengthened glass as the transparent substrate. The silicon nitride film has a refractive index of 1.95 at a wavelength of 600 nm. The silicon oxide film has a refractive index of 1.47 at a wavelength of 600 nm.

  Here, both the silicon nitride film and the silicon oxide film were formed by post-reaction sputtering. That is, after a silicon film was formed using a silicon target, it was reacted with nitrogen, oxygen, or a mixed gas of nitrogen and oxygen activated by a plasma source.

  The silicon nitride film is formed by post-reaction sputtering apparatus: ULVAC, trade name: ULDis, target: p-Si target, deposition gas: argon gas (flow rate: 100 sccm), sputtering power: 6 kW, nitriding source gas: nitrogen gas (Flow rate 100 sccm), nitriding source power: 1.5 kW, substrate temperature: room temperature, film formation rate: 0.2 nm / min. Note that when such film forming conditions are used, the formed film has a compressive stress.

  The film formation of the silicon oxide film is performed by a post-reaction sputtering apparatus: ULVAC, trade name: ULDis, target: p-Si target, film forming gas: argon gas (flow rate 100 sccm), sputtering power: 6 kW, oxidation source gas: oxygen gas (Flow rate 100 sccm), oxidation source power: 1.5 kW, substrate temperature: room temperature, film formation rate: 0.3 nm / min.

<Example 6>
As shown in Table 1, the high refractive index film was changed to a zirconium oxide film (ZrO ₂ film), and the film thickness, ratio (H / L), and the number of stacked layers were changed, and the same as in Example 1 Thus, the cover glass of Example 6 was produced.

  The zirconium oxide film was formed by post-reaction sputtering equipment: ULVAC, trade name: ULDis, target: Zr target, deposition gas: argon gas (flow rate 100 sccm), sputtering power: 6 kW, oxidation source gas: oxygen gas (Flow rate 100 sccm), oxidation source power: 1.5 kW, substrate temperature: room temperature, film formation rate: 0.2 nm / min.

<Comparative Examples 1-3>
As shown in Table 2, the cover glasses of Comparative Examples 1 to 3 were produced in the same manner as in Example 1 except that the film thickness, the ratio (H / L), and the number of laminated layers were changed.

  Next, the following measurements or evaluations were performed on the cover glasses of Examples 1 to 6 and Comparative Examples 1 to 3. The results are shown in Tables 1 and 2.

(Visible light reflectance)
The visible light reflectance defined in JIS R 3106 (1998) was measured on the side of the cover glass on which the antireflection film was formed. Measurement is performed using an ultraviolet-visible spectrophotometer (UV-Spectrophotometer U4100 manufactured by Hitachi High-Technologies Corporation), an incident angle of 5 degrees, a P / S wave mixed light, a scan speed of 600 nm / min, a sampling interval of 1 nm, and a slit. Measurements were taken at 8 nm. For the purpose of eliminating the influence of the reflected light on the side where the antireflection film is not formed, the surface of the cover glass where the antireflection film was not formed was treated with sandblasting and blacked with oily magic.

(Near-infrared light transmittance)
As the transmittance of near-infrared light, the transmittance at 850 nm or 950 nm, which is the central wavelength of typical near-infrared light used in the near-infrared sensor, was measured. Measurement is performed using an ultraviolet-visible spectrophotometer (UV-visible spectrophotometer U4100 manufactured by Hitachi High-Technologies Corporation), an incident angle of 5 degrees, a P / S wave mixed light, a scan speed of 750 nm / min, a sampling interval of 1 nm, and a slit. Measurements were made with automatic control. In the table, the center wavelength is described as the IR sensor center wavelength, and the transmittance of near-infrared light at the center wavelength is described as IR transmittance.
In addition, the continuous wavelength range of at least 10 nm in the wavelength range of 800 to 1200 nm indicates a range of 10 nm or more including the center wavelength. In this example, measurement was performed at a sampling interval of 1 nm, and each measured value of transmittance of near infrared light in a wavelength range of 10 nm or more including the center wavelength was evaluated.

  As is apparent from Table 1, the cover glasses of Examples 1 to 6 have a visible light reflectance of 1.5% or less and 90% in a continuous wavelength range of at least 10 nm including a wavelength of 850 nm or 950 nm. It has the above IR transmittance.

  On the other hand, as is clear from Table 2, the cover glasses of Comparative Examples 1 to 3 cannot obtain an IR transmittance of 90% or more in a continuous wavelength range of at least 10 nm including wavelengths of 850 nm and 950 nm. In addition, the cover glasses of Comparative Examples 1 to 3 do not have a region where the transmittance is 90% or more in a continuous wavelength range of at least 10 nm in the wavelength range of 800 to 1200 nm.

  Although not described in Table 1, in the cover glasses of Examples 1 to 6, each measured value of transmittance at a sampling interval of 1 nm is obtained in a continuous wavelength range of at least 10 nm including a wavelength of 850 nm or 950 nm. It is over 90%.

In addition, the cover glasses of Examples 1 to 6 have a color difference ΔE (L ^* , a ^* , b ^* ) of light reflected by a D65 light source of L ^* a ^* b ^* color system standardized by CIE 1976, √ ( ^{(L *) 2 + (a} *) satisfies the ^{2 + (b *) 2)} ≦ 5. The color difference ΔE (L ^* , a ^* , b ^* ) of reflected light is measured by the visible light reflectance defined in JIS R 3106 (1998) on the side of the cover glass where the antireflection film is formed. did. Measurement is performed using an ultraviolet-visible spectrophotometer (UV-visible spectrophotometer U4100, manufactured by Hitachi High-Technologies Corporation), an incident angle of 5 degrees, a P / S wave mixed light, a scan speed of 600 nm / min, a sampling interval of 1 nm, and a slit. Measurements were taken at 8 nm. The color difference of the reflected light is a value measured without the influence of reflection on the transparent base material 11 side with respect to the antireflection film 12.

  Further, the cover glasses of Examples 1 to 6 have a visible light reflectance of 3% or less at an incident angle of 30 degrees and a visible light reflection at an incident angle of 60 degrees for a wavelength of 850 nm or 950 nm. The rate is 25% or less.

Since the cover glasses of Examples 1 to 6 have a visible light reflectance of 1.5% or less and a transmittance of 90% or more in a continuous wavelength range of at least 10 nm in a wavelength range of 800 to 1200 nm, Good transmission. Therefore, a proximity sensor can be provided around the display device, which is suitable for various electronic devices such as a mobile phone having the display device.
Although the embodiments of the present invention have been described in detail using examples, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention. Is possible.

  DESCRIPTION OF SYMBOLS 10 ... Cover glass, 11 ... Transparent base material, 12 ... Antireflective film, 13 ... High refractive index film, 14 ... Low refractive index film, 20 ... Radical assist sputtering apparatus, 21 ... Apparatus main body, 22 ... Drum, 23 ... Wall , 24 ... target, 26 ... argon gas supply unit, 27 ... radical source, 28 ... matching machine and RF source, 31 ... argon gas supply unit, 32 ... nitrogen gas supply unit, 33 ... oxygen gas supply unit, 35 ... power source , 40 ... mobile phone, 41 ... housing, 42 ... display device, 43 ... cover glass, 45 ... proximity sensor, 451 ... light emitting part, 452 ... light receiving part, 453 ... substrate

Claims (18)

A cover glass for a display device having a transparent base material and an antireflection film provided on the transparent base material,
The antireflection film has a structure in which a high refractive index film having a refractive index of 1.9 or more and a low refractive index film having a refractive index of 1.6 or less are alternately laminated,
The high refractive index film and the low refractive index film are each made of a material containing at least one selected from oxides, nitrides, and oxynitrides of Al, Zr, Ti, Si, Sn, Hf, and Ta. ,
A cover glass for a display device, having a visible light reflectance of 1.5% or less and a transmittance of 90% or more in a continuous wavelength range of at least 10 nm in a wavelength range of 800 to 1200 nm.   The antireflection film has a ratio (H / L) of 2.0 or more of the thickness (H [nm]) of the high refractive index film and the thickness (L [nm]) of the low refractive index film. The cover glass for a display device according to claim 1, comprising at least one laminated unit. 3. The cover glass for a display device according to claim 2, wherein the antireflection film has two or more laminated units having a ratio (H / L) of 2.0 or more. The cover glass for a display device according to claim 1, wherein the total thickness of all the layers of the high refractive index film and all the layers of the low refractive index film is 300 nm or more.   The cover glass for a display device according to claim 1, wherein the thickness of each layer of the high refractive index film is 1 nm or more.   The cover glass for a display device according to claim 1, wherein the thickness of each layer of the low refractive index film is 1 nm or more.   The cover glass for a display device according to claim 1, wherein the total thickness of all the layers of the high refractive index film is 100 nm or more.   The cover glass for a display device according to claim 1, wherein the total thickness of all the layers of the low refractive index film is 100 nm or more.   The cover glass for a display device according to claim 1, wherein the average thickness of all the layers of the high refractive index film is 30 nm or more. The cover glass for a display device according to claim 1, wherein the average thickness of all the layers of the low refractive index film is 25 nm or more.   The said transparent base material consists of inorganic glass, The cover glass for display apparatuses as described in any one of Claims 1-10 characterized by the above-mentioned.   The said transparent base material consists of tempered glass, The cover glass for display apparatuses as described in any one of Claims 1-10 characterized by the above-mentioned.   The said transparent base material consists of sapphire glass, The cover glass for display apparatuses as described in any one of Claims 1-10 characterized by the above-mentioned. The L ^* value, a ^* value, and b ^* value in the L ^* a ^* b ^* color space of the reflected light are
√ ((L ^* ) ² + (a ^* ) ² + (b ^* ) ² ) ≦ 5
The cover glass for a display device according to any one of claims 1 to 10, wherein: An apparatus body having a display device;
An electronic apparatus comprising: the cover glass for a display device according to claim 1, which is provided so as to cover the display device.   16. The electronic apparatus according to claim 15, further comprising a proximity sensor that uses near infrared light.   The electronic device according to claim 15 or 16, wherein the electronic device is a portable information terminal.   The electronic device according to claim 17, wherein the portable information terminal is a portable phone.

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