JP7563019B2 - Coverslips - Google Patents

Description

The present invention relates to a cover glass with anti-glare function.

Cover glass is widely used in displays for mobile phones, tablet devices, televisions, etc. The visibility of such displays can be reduced due to reflections of external light, etc. A method for reducing reflections on displays and improving visibility is known to provide an anti-glare layer with an uneven surface structure. Furthermore, a method for improving anti-glare effects and contrast is known to provide an anti-reflection film.

For example, the following Patent Document 1 discloses a method of forming an uneven shape on the surface of a transparent substrate to provide an anti-glare treatment and a method of providing a low-reflection film. The low-reflection film described is a laminate in which a high-refractive index layer and a low-refractive index layer are laminated together.

Patent No. 5839134

In recent years, there has been a demand for displays such as smartphones and digital signage to further reduce the reflection of external light and to further improve visibility. However, even the cover glass of Patent Document 1 cannot sufficiently reduce the reflection of external light, and there is a problem in that it is still not possible to sufficiently improve visibility.

The object of the present invention is to provide a cover glass that can effectively improve visibility.

The cover glass according to the first invention of the present application comprises a glass substrate, an anti-glare layer having a concave-convex structure provided on the glass substrate, and an anti-reflection film provided on the anti-glare layer, and is characterized in that when light is incident from the anti-reflection film side, the luminous reflectance of the regular reflected light is smaller than the luminous reflectance of the reflected scattered light.

The cover glass according to the second invention of the present application comprises a glass substrate, an anti-glare layer provided on the glass substrate, and an anti-reflection film provided on the anti-glare layer, and is characterized in that the glass substrate and the anti-glare layer have different compositions.

Hereinafter, the first and second inventions may be collectively referred to as the present invention.

In the present invention, it is preferable that the absolute value of the difference between the refractive index of the glass substrate and the refractive index of the anti-glare layer is 0.02 or more.

In the present invention, it is preferable that the anti-glare layer has flat and non-flat portions.

In the present invention, it is preferable that the thickness of the flat portion is 5 nm or more and 500 nm or less.

In the present invention, it is preferable that the luminous reflectance of reflected light from a first laminate structure in which the flat portion of the anti-glare layer and the anti-reflection film are provided in this order on the glass substrate is smaller than the luminous reflectance of a second laminate structure in which the anti-reflection film is provided on the non-flat portion of the anti-glare layer.

In the present invention, it is preferable that an optical adjustment layer having a refractive index different from that of the glass substrate is provided between the glass substrate and the anti-glare layer.

In the present invention, it is preferable that the absolute value of the difference between the refractive index of the optical adjustment layer and the refractive index of the anti-glare layer is 0.2 or more.

The present invention provides a cover glass that can effectively improve visibility.

1 is a schematic cross-sectional view showing a cover glass according to a first embodiment of the present invention. 5A and 5B are schematic cross-sectional views for explaining a method for measuring the luminous reflectance of specularly reflected light. 5A and 5B are schematic cross-sectional views for explaining a method for measuring the luminous reflectance of reflected scattered light. 1 is a schematic cross-sectional view illustrating a first laminate in which a flat portion of an anti-glare layer and an anti-reflection film are laminated in this order on a glass substrate. FIG. 4 is a schematic cross-sectional view illustrating a second laminate formed by laminating an anti-reflection film on a non-flat portion on an anti-glare layer. FIG. FIG. 4 is a schematic cross-sectional view showing a cover glass according to a second embodiment of the present invention. 11 is a schematic cross-sectional view illustrating a third laminate in which an optical adjustment layer, an anti-glare layer, and an anti-reflection film are laminated in this order on a glass substrate. FIG.

The following describes preferred embodiments. 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 function may be referred to by the same reference numerals. In the following drawings, A is incident light, B is specularly reflected light, and C is reflected scattered light.

First Embodiment
Fig. 1 is a schematic cross-sectional view showing a cover glass according to a first embodiment of the present invention. As shown in Fig. 1, the cover glass 1 includes a glass substrate 2, an anti-glare layer 3, and an anti-reflection film 4. The anti-glare layer 3 is provided on the glass substrate 2. In addition, the anti-reflection film 4 is provided on the anti-glare layer 3.

In this embodiment, the glass substrate 2 has a substantially rectangular plate shape. However, the glass substrate 2 may have a shape such as a substantially circular plate shape, and the shape is not particularly limited.

The thickness of the glass substrate 2 is not particularly limited and can be set appropriately depending on factors such as light transmittance. The thickness of the glass substrate 2 can be, for example, about 0.1 mm to 3 mm.

The glass used for the glass substrate 2 is not particularly limited, and examples that can be used include borosilicate glass, alkali-free glass, aluminosilicate glass, and chemically strengthened glass.

The glass substrate 2 has a first main surface 2a and a second main surface 2b. The first main surface 2a and the second main surface 2b face each other. An anti-glare layer 3 is provided on the first main surface 2a of the glass substrate 2. The anti-glare layer 3 has an uneven structure. The anti-glare layer 3 is provided to provide a so-called anti-glare effect, which suppresses reflection of external light, etc.

In this embodiment, the anti-glare layer 3 is an inorganic film. Such an anti-glare layer 3 can be formed by applying an inorganic paint to the glass substrate 2 and drying it. In this embodiment, the anti-glare layer 3 is formed by applying the inorganic paint by a spray coating method and drying it. Note that the method of applying the inorganic paint is not limited to the spray coating method, and other application methods may be used.

In this embodiment, the inorganic paint is composed of a silica precursor. However, the inorganic paint may be composed of, for example, an alumina precursor, a zirconia precursor, a titania precursor, or the like. These precursors may be used alone or in combination. In addition, the solvent for the inorganic paint may be, for example, water, alcohol, or the like.

Examples of silica precursors include alkoxysilanes such as tetraethoxysilane and tetramethoxysilane, hydrolysis condensates of alkoxysilanes (sol-gel silica), and silazanes. From the viewpoint of further enhancing the anti-glare effect, alkoxysilanes such as tetraethoxysilane and tetramethoxysilane, and hydrolysis condensates thereof are preferred, and a hydrolysis condensate of tetraethoxysilane is more preferred.

Alumina precursors include aluminum alkoxides, hydrolysis condensates of aluminum alkoxides, water-soluble aluminum salts, aluminum chelates, etc.

Examples of zirconia precursors include zirconium alkoxides and hydrolysis condensates of zirconium alkoxides.

Titania precursors include titanium alkoxides and hydrolysis condensates of titanium alkoxides.

The inorganic coating may also contain inorganic particles. Examples of inorganic particles include silica particles, alumina particles, zirconia particles, titania particles, hafnia particles, and yttria particles.

The average thickness of the anti-glare layer 3 is not particularly limited. However, from the viewpoint of further enhancing the anti-glare effect, the average thickness of the anti-glare layer 3 is preferably 0.1 μm or more and 2 μm or less, more preferably 0.15 μm or more and 1.75 μm or less, and even more preferably 0.2 μm or more and 1 μm or less.

The anti-reflection film 4 is preferably a dielectric multilayer film. In this case, the image clarity on a display or the like can be further improved. In this embodiment, the anti-reflection film 4 is a dielectric multilayer film in which a high refractive index film 5 with a relatively high refractive index and a low refractive index film 6 with a relatively low refractive index are alternately laminated in this order. The anti-reflection film 4 may also be a dielectric multilayer film in which a low refractive index film 6 with a relatively low refractive index and a high refractive index film 5 with a relatively high refractive index are alternately laminated in this order.

Examples of materials for the high refractive index film 5 include niobium oxide, titanium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silicon nitride, aluminum oxide, and aluminum nitride, as in this embodiment.

Examples of materials for the low refractive index film 6 include silicon oxide and aluminum oxide.

The thickness of each layer constituting the anti-reflection film 4 is preferably 1 nm or more and 500 nm or less, more preferably 2 nm or more and 300 nm or less, and even more preferably 5 nm or more and 200 nm or less.

The total number of layers constituting the anti-reflective coating 4 is preferably 2 to 7 inclusive. By keeping it within this range, it is possible to produce an effective and easily formed film.

The total thickness of the anti-reflection film 4 is preferably 50 nm or more and 1000 nm or less, more preferably 75 nm or more and 750 nm or less, and even more preferably 100 nm or more and 500 nm or less.

The anti-reflective coating 4 can be formed, for example, by a sputtering method, a CVD method, or a vacuum deposition method.

In the cover glass 1 of this embodiment, when incident light A is incident from the anti-reflection film 4 side, the luminous reflectance of the specularly reflected light B is smaller than the luminous reflectance of the reflected scattered light C. Therefore, the cover glass 1 can effectively suppress the reflection of external light, and can effectively improve visibility in displays, etc. Below, a method for measuring the luminous reflectance of the specularly reflected light B and the luminous reflectance of the reflected scattered light C in the cover glass 1 will be described with reference to Figures 2 and 3.

2(a) and (b) are schematic cross-sectional views for explaining a method for measuring the luminous reflectance of specular light. First, the reflected light intensity X1 of the specularly reflected light B in the cover glass 1 shown in FIG. 2(a) is measured. When measuring the reflected light intensity X1 of the specularly reflected light B, a process is performed to suppress the back surface reflection of the cover glass 1 so that the back surface reflection does not affect the measurement. Next, as shown in FIG. 2(b), the reflected light intensity Y1 of the specularly reflected light B is measured in a state in which an aluminum film 8 (thickness: about 300 nm) is formed on the upper surface of the anti-reflection film 4 of the cover glass 1. Then, the reflection spectrum of the specularly reflected light B can be measured from the ratio X1/Y1 of these reflected light intensities. The reflected light intensities X1 and Y1 of the specularly reflected light B can be measured, for example, by a spectrophotometer with an incident angle of the incident light of 8°, an angle of the reflected light received of 8°, a measurement wavelength of 380 nm to 800 nm, and a measurement wavelength interval of 1 nm. From the measured reflection spectrum, the luminous reflectance of specularly reflected light B for a D65 light source can be calculated in accordance with JIS Z8722:2009.

Figures 3(a) and (b) are schematic cross-sectional views for explaining a method for measuring the visual reflectance of reflected scattered light. First, the reflected light intensity X2 of the reflected scattered light C in the cover glass 1 shown in Figure 3(a) is measured. When measuring the reflected light intensity X2 of the reflected scattered light C, a process is performed to suppress the back surface reflection of the cover glass 1 so that the back surface reflection does not affect the measurement. Next, as shown in Figure 3(b), the reflected light intensity Y2 of the reflected scattered light C is measured in a state in which an aluminum film 8 is formed on the upper surface of the anti-reflection film 4 of the cover glass 1. Then, the reflection spectrum of the reflected scattered light C can be measured from the ratio X2/Y2 of these reflected light intensities. The reflected light intensities X2 and Y2 of the reflected scattered light C can be measured, for example, by a spectrophotometer with the incident angle of the incident light being 8°, the angle of the received reflected light being 11°, the measurement wavelength being 380 nm to 800 nm, and the measurement wavelength interval being 1 nm. From the measured reflectance spectrum, the luminous reflectance of reflected scattered light C for a D65 light source can be calculated in accordance with JIS Z8722:2009.

Conventionally, when an anti-glare layer or anti-reflection film is provided on a glass substrate, reflection occurs at each interface, resulting in complex reflection characteristics. In response to this, the inventors have focused on the reflection spectrum of specularly reflected light B and reflected scattered light C, and discovered that by making the visual reflectance of specularly reflected light B smaller than the visual reflectance of reflected scattered light C, it is possible to effectively suppress the glare of external light and effectively improve visibility.

The inventors also discovered that the reflection spectrum of the regular reflection light B is generated by the structure of the first laminate 10 shown in FIG. 4, that is, the laminate structure in which the flat portion of the anti-glare layer 3 and the anti-reflection film 4 are laminated in this order on the glass substrate 2. The inventors also discovered that the reflection spectrum of the reflected scattered light C is generated by the structure of the second laminate 11 shown in FIG. 5, that is, the laminate structure in which the anti-reflection film 4 is laminated on the non-flat portion of the anti-glare layer 3.

Therefore, the luminous reflectance of the regular reflected light B can be determined from the luminous reflectance of the reflected light due to the structure of the first laminate 10 in which the flat portion of the anti-glare layer 3 and the anti-reflection film 4 are laminated in this order on the glass substrate 2. The luminous reflectance of the reflected scattered light C can be determined from the luminous reflectance due to the structure of the second laminate 11 in which the anti-reflection film 4 is laminated on the non-flat portion of the anti-glare layer 3.

Therefore, the luminous reflectance of the specularly reflected light B can be adjusted by designing the first laminate 10, which is formed by laminating the flat portion of the anti-glare layer 3 and the anti-reflection film 4 in this order on the glass substrate 2. The luminous reflectance of the specularly reflected light B can be adjusted by the refractive index of each layer, in particular the material constituting each layer, the thickness of each layer, etc.

The luminous reflectance of the reflected scattered light C can be adjusted by designing the second laminate 11, which is formed by laminating the anti-reflection film 4 on the non-flat portion of the anti-glare layer 3. The luminous reflectance of the reflected scattered light C can be adjusted by the refractive index of each layer, particularly the material constituting each layer, the thickness of each layer, etc.

By designing the thickness of the anti-reflection film 4, and in particular the thickness and material of the high refractive index film 5 and low refractive index film 6, so that the visual reflectance of the first laminate 10 is as low as possible, the visual reflectance of the regular reflected light B can be made smaller than the visual reflectance of the reflected scattered light C.

In the cover glass 1 of this embodiment, the difference between the visual reflectance of the reflected scattered light C and the visual reflectance of the specularly reflected light B is preferably 0.01% or more, and more preferably 0.05% or more. In this case, the reflection of external light can be more effectively suppressed, and visibility can be more effectively improved. The upper limit of the difference between the visual reflectance of the reflected scattered light C and the visual reflectance of the specularly reflected light B can be, for example, 1%.

In another aspect of the cover glass 1 of this embodiment, the composition of the glass substrate 2 and the anti-glare layer 3 are different. Even in this case, the reflection of external light can be effectively suppressed, and visibility can be effectively improved.

In the present invention, the absolute value of the difference between the refractive index of the glass substrate 2 and the refractive index of the anti-glare layer 3 is preferably 0.02 or more, and more preferably 0.05 or more. In this case, the reflection of external light can be more effectively suppressed, and visibility can be more effectively improved. In addition, from the viewpoint of more effectively improving visibility, it is preferable that the refractive index of the anti-glare layer 3 is smaller than the refractive index of the glass substrate 2.

In addition, by adjusting the thickness of the anti-reflection film 4, and in particular the thickness and materials of the high refractive index film 5 and low refractive index film 6, it is possible to more effectively suppress reflections of external light and more effectively improve visibility.

The anti-glare layer 3 preferably has a flat portion. Here, the flat portion refers to a portion where the frequency distribution of the height of the unevenness on the surface of the anti-glare layer 3 is within ±20 nm of the most frequent height. In this case, the reflection of external light can be more effectively suppressed, and visibility can be more effectively improved. In this case, the thickness of the flat portion can be preferably 5 nm or more, more preferably 10 nm or more, preferably 500 nm or less, and more preferably 200 nm or less. In addition, in a plan view, the area of the flat portion relative to the area of the entire anti-glare layer 3 can be, for example, 15% or more and 60% or less. Note that the non-flat portion refers to a portion other than the flat portion. In addition, in the frequency distribution of the height of the unevenness on the surface of the anti-glare layer 3, if the load area ratio at a height 50 nm lower than the most frequent height is 0.9 or less, and the load area ratio at a height 50 nm higher than the most frequent height is 0.1 or more, the anti-glare layer 3 is considered to have no flat portion.

Second Embodiment
6 is a schematic cross-sectional view showing a cover glass according to a second embodiment of the present invention. As shown in FIG. 6, in the cover glass 21, an optical adjustment layer 7 is provided between the glass substrate 2 and the anti-glare layer 3. In this embodiment, the optical adjustment layer 7 is a high refractive index layer having a relatively high refractive index. However, the optical adjustment layer 7 may be a low refractive index layer having a relatively low refractive index, as long as it is a layer having a refractive index different from that of the glass substrate 2. Other points are the same as those of the first embodiment.

Even in the cover glass 21, the luminous reflectance of the regular reflected light B is smaller than the luminous reflectance of the reflected scattered light C, so that the reflection of external light can be effectively suppressed, and the visibility of displays, etc. can be effectively improved.

In this case, as shown in FIG. 7, the luminous reflectance of the specularly reflected light B can be adjusted by designing the third laminate 30 in which an optical adjustment layer 7, an anti-glare layer 3, and an anti-reflection film 4 are laminated in this order on a glass substrate 2. The luminous reflectance of the specularly reflected light B can be adjusted by the refractive index of each layer, particularly the material constituting each layer, the thickness of each layer, etc.

The luminous reflectance of the reflected scattered light C can be adjusted by designing the second laminate 11, which is formed by laminating the anti-reflection film 4 on the anti-glare layer 3. The luminous reflectance of the reflected scattered light C can be adjusted by the refractive index of each layer, in particular the material constituting each layer, the thickness of each layer, etc.

The absolute value of the difference between the refractive index of the anti-glare layer 3 and the refractive index of the optical adjustment layer 7 is preferably 0.2 or more, and more preferably 1.0 or more. In this case, the reflection of external light can be more effectively suppressed, and visibility can be more effectively improved. In addition, from the viewpoint of more effectively improving visibility, it is preferable that the refractive index of the anti-glare layer 3 is smaller than the refractive index of the optical adjustment layer 7.

The present invention is not limited to the configurations of the first and second embodiments. For example, other layers may be provided on the anti-reflection film 4. Examples of other layers include an anti-fouling layer. The anti-fouling layer preferably contains an organosilicon compound. By containing an organosilicon compound, the adhesion to the anti-reflection film 4 can be further improved. This makes it difficult for the anti-fouling layer to peel off even after long-term use.

The organosilicon compound may be, for example, one or more compounds selected from a silane coupling agent, a silicone oil, a silicone resin, a silicone rubber, hydrophobic silica, and a fluorine-containing organosilicon compound.

The thickness of the antifouling layer is preferably 0.5 nm or more and 20 nm or less, more preferably 0.75 nm or more and 15 nm or less, and even more preferably 1 nm or more and 10 nm or less.

The method for forming the antifouling layer is not particularly limited, and it can be formed, for example, by applying a diluted solution of an organosilicon compound or the like by a spray coating method or the like.

The present invention will be described in more detail below based on specific examples. The present invention is not limited to the following examples, and can be modified as appropriate within the scope of the gist of the invention.

Example 1
First, a glass substrate (manufactured by Nippon Electric Glass Co., Ltd., product number "T2X-1", refractive index: 1.50) was prepared. Next, a coating agent containing a silica precursor was applied onto the glass substrate by a spray coating method to form an anti-glare layer (refractive index: 1.44) having a thickness of 20 nm. The amount of the coating agent applied was 35 ml/ ^m2 . The difference between the refractive index of the glass substrate and the refractive index of the anti-glare layer was 0.06. The area ratio of the flat portion was 47%.

Next, a high refractive index film made of niobium oxide (Nb ₂ O ₅ ) having a thickness of 12.73 nm was formed on the anti-glare layer by a sputtering method. Next, a low refractive index film made of silicon oxide (SiO ₂ ) having a thickness of 34.84 nm was formed by a sputtering method. Next, a high refractive index film made of niobium oxide (Nb ₂ O ₅ ) having a thickness of 113.44 nm was formed by a sputtering method. Next, a low refractive index film made of silicon oxide (SiO ₂ ) having a thickness of 85.45 nm was formed by a sputtering method. As a result, a dielectric multilayer film in which high refractive index films and low refractive index films were alternately stacked in a total of four layers was produced, and a cover glass was obtained.

Example 2
First, a glass substrate (manufactured by Nippon Electric Glass Co., Ltd., product number "T2X-1", refractive index: 1.50) was prepared. Next, an optical adjustment layer (refractive index: 2.35) made of niobium oxide (Nb ₂ O ₅ ) having a thickness of 2.36 nm was formed on the anti-glare layer by a sputtering method.

Next, a coating agent containing a silica precursor was applied onto the glass substrate by spray coating to form an anti-glare layer (refractive index: 1.44) having a thickness of 54 nm. The amount of inorganic coating material applied was 70 ml/ ^m2 . The difference between the refractive index of the optical adjustment layer and the refractive index of the anti-glare layer was 0.85. The area ratio of the flat portion was 21%.

Next, a high refractive index film made of niobium oxide (Nb ₂ O ₅ ) having a thickness of 16.13 nm was formed on the anti-glare layer by a sputtering method. Next, a low refractive index film made of silicon oxide (SiO ₂ ) having a thickness of 36.77 nm was formed by a sputtering method. Next, a high refractive index film made of niobium oxide (Nb ₂ O ₅ ) having a thickness of 114.61 nm was formed by a sputtering method. Next, a low refractive index film made of silicon oxide (SiO ₂ ) having a thickness of 86.09 nm was formed by a sputtering method. As a result, an anti-reflection film consisting of a total of four layers of high refractive index films and low refractive index films alternately stacked was produced, and a cover glass was obtained.

(Comparative Example 1)
An anti-glare layer was formed on a glass substrate in the same manner as in Example 1. Next, an anti-reflection film was prepared by sputtering on the anti-glare layer, which was a total of five layers of a low refractive index film made of silicon oxide (SiO ₂ ) having a thickness of 45 nm, a high refractive index film made of niobium oxide (Nb ₂ O ₅ ) having a thickness of 10.37 nm, a low refractive index film made of silicon oxide (SiO ₂ ) having a thickness of 36.21 nm, a high refractive index film made of niobium oxide (Nb ₂ O ₅ ) having a thickness of 109.45 nm, and a low refractive index film made of silicon oxide (SiO ₂ ) having a thickness of 81.44 nm, which were alternately laminated in this order, to obtain a cover glass.

(Comparative Example 2)
A cover glass was obtained in the same manner as in Example 1, except that no anti-reflection film was provided.

(Comparative Example 3)
A glass substrate (manufactured by Nippon Electric Glass Co., Ltd., product number "T2X-1", refractive index: 1.50) was etched to perform an anti-glare treatment. Next, on the anti-glare treated glass substrate, an anti-reflection film was produced by a sputtering method, which was composed of a total of four layers of a high refractive index film made of niobium oxide (Nb ₂ O ₅ ) having a thickness of 10.3 nm, a low refractive index film made of silicon oxide (SiO ₂ ) having a thickness of 36.21 nm, a high refractive index film made of niobium oxide (Nb ₂ O ₅ ) having a thickness of 109.45 nm, and a low refractive index film made of silicon oxide (SiO ₂ ) having a thickness of 81.44 nm, alternately stacked in this order, to obtain a cover glass.

(Comparative Example 4)
A glass substrate (manufactured by Nippon Electric Glass Co., Ltd., product number "T2X-1", refractive index: 1.50) was etched to perform an anti-glare treatment, thereby obtaining a cover glass.

(Comparative Example 5)
A glass substrate (manufactured by Nippon Electric Glass Co., Ltd., product number "T2X-1", refractive index: 1.50) was used as it was as raw glass.

<Evaluation>
(Luminous reflectance)
The luminous reflectance of the regular reflected light and the reflected scattered light was measured using a spectrophotometer (Hitachi High-Tech Science Corporation, product number "U-4000"). Specifically, the luminous reflectance of the regular reflected light was measured at an incident angle of 8°, a receiving angle of 8°, a measurement wavelength of 380 nm to 800 nm, and a measurement interval of 1 nm, and the luminous reflectance of the regular reflected light with respect to the D65 light source was obtained from the measured reflection spectrum in accordance with JIS Z8722:2009. The luminous reflectance of the reflected scattered light was measured at an incident angle of 8°, a receiving angle of 11°, a measurement wavelength of 380 nm to 800 nm, and a measurement interval of 1 nm, and the luminous reflectance of the reflected scattered light with respect to the D65 light source was obtained from the measured reflection spectrum in accordance with JIS Z8722:2009. The results are shown in Table 1 below. In Table 1 below, the standard regular reflectance of the raw glass is also shown. The reference specular reflectance of plain glass was calculated by calculating the average value (average reflectance) of the reflectance in the measurement wavelength range from the reflection spectrum of specular light, and calculating the ratio to the average reflectance of plain glass (Comparative Example 5).

(Flat area ratio)
Using a laser microscope VK-X260 manufactured by KEYENCE, the height of the unevenness of the anti-glare layer was measured in a measurement range of 95 μm × 71 μm with a 150x objective lens. Next, the frequency distribution of the measured height data was obtained, and the most frequent height was shifted and corrected to 0. The area of the region where the corrected height was -20 nm or more and +20 nm or less was obtained, and this was taken as the area of the flat part. The area of the obtained flat part was divided by the area of the measurement range of the laser microscope to obtain the area ratio of the flat part.

(Reflection index value)
The reflection index value C: Clarity was measured in a reflection distribution measurement mode using an SMS-1000 (manufactured by Display-Messtechnik & Systeme). A lens with a focal length of 16 mm was used, the angle of incidence of the incident light was set to 3°, and the distance from the irradiation position on the cover glass of the examples and comparative examples to the lens was set to 410 mm. The cover glass of the examples and comparative examples was attached to a blackboard glass with an immersion liquid with a refractive index of 1.53 applied to the back surface thereof, and the measurement was performed.

(Sensory Test)
Regarding anti-glare properties, when a line light source was reflected, those in which the outline of the reflected line light source was not discernible were rated as "A," those in which the outline was barely discernible were rated as "B," those in which the outline was discernible to some extent were rated as "C," and those in which the outline was clearly discernible were rated as "D."

Regarding image clarity, an arbitrary photographic image was displayed on a display device with a resolution of 264 ppi, and an evaluation sample was placed so as to cover half of it. The photographic image and the photographic image viewed through the evaluation sample were compared. Those in which no difference could be discerned were given an "A", those in which the difference was slight but discernible were given a "B", those in which slight degradation of the photographic image viewed through the evaluation sample was felt were given a "C", those in which degradation of the photographic image viewed through the evaluation sample was felt were given a "D", and those in which significant degradation of the photographic image viewed through the evaluation sample was felt were given an "E".

The results are shown in Table 1 below.

From Table 1, it can be seen that in Examples 1 and 2, the sensory test evaluation was either "A" or "B," and it was confirmed that visibility was improved. On the other hand, in Comparative Examples 1 to 5, the sensory test evaluation was either "C," "D," or "E," and visibility could not be sufficiently improved.

Reference Signs List 1, 21... Cover glass 2... Glass substrate 2a... First main surface 2b... Second main surface 3... Anti-glare layer 4... Anti-reflection film 5... High refractive index film 6... Low refractive index film 7... Optical adjustment layer 8... Aluminum film 10... First laminate 11... Second laminate 30... Third laminate

Claims (5)

A glass substrate;
an anti-glare layer having a concave-convex structure provided on the glass substrate;
an anti-reflection film provided on the anti-glare layer;
an optical adjustment layer provided between the glass substrate and the anti-glare layer and having a refractive index different from that of the glass substrate;
Equipped with
the anti-glare layer has a flat portion and a non-flat portion,
In a plan view, a ratio of an area of the flat portion to an area of the entire anti-glare layer is 15% or more and 60% or less,
The refractive index of the optical adjustment layer is greater than the refractive index of the anti-glare layer,
an absolute value of a difference between a refractive index of the optical adjustment layer and a refractive index of the antiglare layer is 0.2 or more;
A cover glass, in which when light is incident from the antireflection film side, the luminous reflectance of regular reflected light is smaller than the luminous reflectance of reflected scattered light. The cover glass according to claim 1, wherein the absolute value of the difference between the refractive index of the glass substrate and the refractive index of the anti-glare layer is 0.02 or more. The cover glass according to claim 1 or 2 , wherein the flat portion has a thickness of 5 nm or more and 500 nm or less. The cover glass according to any one of claims 1 to 3, wherein the luminous reflectance of reflected light due to a first laminate structure in which a flat portion of the anti-glare layer and the anti-reflection film are provided in this order on the glass substrate is smaller than the luminous reflectance due to a second laminate structure in which the anti- reflection film is provided on a non-flat portion of the anti-glare layer. The cover glass according to any one of claims 1 to 4 , wherein the optical adjustment layer is made of niobium oxide.

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