JP2023056723A - Transparent article - Google Patents

Abstract

To provide a transparent article which can provide a reflection prevention effect and also can be manufactured more easily.SOLUTION: A transparent article 10 includes: a transparent base material 11 with a main surface 11a; and an anti-glare layer 12 in the main surface 11a, the anti-glare layer having an irregular structure 20 in a surface. The index of refraction of the anti-glare 12 is different from that of the transparent base material 11. Also, in the anti-glare layer 12, the thickness of the optical film for the wavelength 550 nm of the anti-glare film thickness t is at least 43 nm and not larger than 101 nm and the height h of the anti-glare as the height of protrusion of a protruding part 22 of the irregular structure 20 is at least 110 nm and not larger than 180 nm.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a transparent article provided on a display surface of, for example, a display device.

For example, as shown in Patent Document 1, from the viewpoint of improving the visibility of the display device, the surface of a transparent article such as a cover glass disposed on the display surface of the display device is used as an antiglare surface to impart an antiglare effect. is proposed. The anti-glare effect of the anti-glare surface is exhibited based on the uneven structure of the anti-glare surface. Further, Patent Literature 1 discloses applying an antireflection film to an antiglare surface of a transparent article. An anti-glare effect can be obtained by the anti-reflection effect of this anti-reflection film.

Japanese Patent No. 5839134

However, an antireflection film for obtaining a sufficient antireflection effect must be, for example, a dielectric multilayer film having four or more layers. Since it is necessary to use a vacuum process such as a sputtering method for depositing the dielectric multilayer film, it has been a factor that complicates the production of the transparent article with the antireflection film.

SUMMARY OF THE INVENTION An object of the present invention is to provide a transparent article capable of obtaining an antireflection effect while facilitating its manufacture.

A transparent article for solving the above problems includes a transparent base material having a main surface, and an anti-glare layer provided on the main surface and having an uneven structure on the surface, wherein the anti-glare layer has a refractive index equal to that of the transparent base material. The anti-glare layer has an optical film thickness of 43 nm or more and 101 nm or less at a wavelength of 550 nm in the recesses of the uneven structure, and the protrusion height of the protrusions of the uneven structure is 110 nm or more. , and 180 nm or less.

According to this configuration, as shown in FIG. 9, it is possible to keep the luminous reflectance of the surface of the antiglare layer low. As a result, it is possible to obtain a sufficient antireflection effect by the antiglare layer while facilitating the production of a transparent article by eliminating the need for an antireflection film composed of a dielectric multilayer film or the like, which is complicated to form.

In the above transparent article, it is preferable that the arithmetic mean height Sa of the concave-convex structure is 20 nm or more and 200 nm or less.
According to this configuration, it is possible to more preferably suppress the glare in the antiglare layer.

In the above transparent article, it is preferable that the average length RSm of the roughness curvilinear element of the concave-convex structure is 5 μm or more and 40 μm or less.
According to this configuration, it is possible to more preferably suppress the glare in the antiglare layer.

In the above transparent article, it is preferable that an antifouling layer is provided on the surface of the uneven structure of the antiglare layer.
According to this configuration, it is possible to suppress adhesion of dirt to the surface of the antiglare layer by the antifouling layer.

In the above transparent article, it is preferable that the surface of the uneven structure of the antiglare layer does not have a dielectric multilayer film.
According to this configuration, it is possible to facilitate the manufacture of transparent articles.

According to the transparent article of the present invention, it is possible to obtain an antireflection effect while facilitating manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the transparent article of embodiment. 4 is a graph showing a height distribution function; It is a schematic diagram which shows the 1st sample used by a measurement step. FIG. 4 is a schematic diagram showing a second sample used in the measurement step; It is a schematic diagram which shows the measuring apparatus used at a measuring step. 10 is a graph showing a first sample specular reflectance spectrum; FIG. 4 is a graph showing a second sample specular reflectance spectrum; FIG. FIG. 4 is an explanatory diagram for explaining a method of calculating reflectance R; 4 is a graph showing the relationship between antiglare height and luminous reflectance in transparent articles.

An embodiment of the transparent article will be described below with reference to the drawings. In the drawings, for convenience of explanation, part of the configuration may be exaggerated or simplified. Also, the dimensional ratio of each part may differ from the actual one.

A transparent article 10 of the present embodiment shown in FIG. 1 is used, for example, by arranging it on the display surface of a display device. In this case, the transparent article 10 may be a member attached on the display surface of the display device. That is, the transparent article 10 may be a member that is attached to the display device afterward.

The transparent article 10 includes a transparent substrate 11 having a main surface 11a, and a translucent anti-glare layer 12 provided on the main surface 11a and having an uneven structure 20 on its surface. The uneven structure 20 on the surface of the antiglare layer 12 is formed, for example, by spraying a liquid containing a silica component onto the main surface 11a of the transparent substrate 11 by a spray method. It should be noted that other methods for forming the uneven structure 20 include a process of applying a coating agent, a blasting process, an etching process, and the like.

The transparent substrate 11 has, for example, a sheet shape or a plate shape. The transparency of the transparent base material 11 means, for example, that it transmits 80% or more of visible light (wavelength range of 400 to 700 nm) on average. The material of the transparent substrate 11 is not particularly limited. Examples of the material of the transparent substrate 11 include glass and resin. The material of the transparent substrate 11 is preferably glass, and as the glass, known glass such as alkali-free glass, borosilicate glass, aluminosilicate glass, soda lime glass, and chemically strengthened glass can be used. . The transparent substrate 11 is preferably made of glass because the transmittance of visible light is less likely to change over time.

The refractive index of the antiglare layer 12 is different from that of the transparent substrate 11 . For example, the antiglare layer 12 is set to have a smaller refractive index for the same wavelength than the transparent substrate 11 . More specifically, the transparent base material 11 has a refractive index of about 1.52 at a wavelength of 550 nm, while the antiglare layer 12 has a refractive index of about 1.44 at the same wavelength. The refractive index of each of the transparent base material 11 and the antiglare layer 12 can be appropriately changed according to the properties required for the transparent article 10 .

As described above, since the refractive index of the anti-glare layer 12 is different from that of the transparent substrate 11, the light reflected on the surface of the anti-glare layer 12 and the boundary surface 13 between the anti-glare layer 12 and the transparent substrate 11 Anti-glare effect is exhibited by interference with reflected light. Furthermore, since interference of reflected light also occurs due to the uneven structure 20 of the anti-glare layer 12, a more effective anti-glare effect is exhibited.

The transparent article 10 does not have, for example, four or more dielectric multilayer films on the surface of the uneven structure 20, but may have a layer other than the dielectric multilayer film, such as an antifouling layer, on the surface of the uneven structure 20. good. For example, the transparent article 10 of this embodiment has the antifouling layer 14 on the surface of the uneven structure 20 . The antifouling layer 14 is made of, for example, a fluorine-containing organosilicon compound.

(Antiglare film thickness t and antiglare height h)
The uneven structure 20 of the antiglare layer 12 has recesses 21 and protrusions 22 . The features of the uneven structure 20 of the anti-glare layer 12 can be represented by the anti-glare film thickness t, which is the film thickness at the concave portions 21 , and the anti-glare height h, which is the protrusion height of the convex portions 22 . The antiglare film thickness t is the physical film thickness from the interface 13 to the surface of the recess 21 . When indicating the effective range of the antiglare film thickness t, the range is defined by the optical film thickness represented by (physical film thickness)×(refractive index).

The antiglare film thickness t and the antiglare height h can be defined by the height distribution function H(x) shown in the following formula (1).

上記式（１）に示すように、高さ分布関数Ｈ（ｘ）は、３つの正規分布関数Ｇ_１，Ｇ_２，Ｇ_３と、歪みを与えるための２つのシグモイド関数Ｓ_１，Ｓ_２とを合成した関数である。上記式（１）において、ｋ_２，ｋ_３は比例定数である。

As shown in the above formula (1), the height distribution function H(x) consists of three normal distribution functions G ₁ , G ₂ and G ₃ and two sigmoid functions S ₁ and S ₂ for giving distortion. is a function that combines In the above formula (1), k ₂ and k ₃ are proportionality constants.

Each normal distribution function G ₁ , G ₂ , G ₃ is represented by the following formula (2), and each sigmoid function S ₁ , S ₂ is represented by the following formula (3).

上記式（２）において、ｄはシフト量であり、σは標準偏差である。上記式（３）において、ａはゲインであり、ｄはシフト量である。

In the above formula (2), d is the shift amount and σ is the standard deviation. In the above equation (3), a is the gain and d is the shift amount.

FIG. 2 shows an example of the height distribution function H(x). As shown in the figure, the height distribution function H(x) is expressed as a histogram showing the frequency of each height in the antiglare layer 12 . The height on the horizontal axis is the height with reference to the interface 13 between the antiglare layer 12 and the transparent substrate 11 .

Each parameter in the height distribution function H(x) shown in FIG. 2 is shown in Tables 1 and 2 below.

The antiglare film thickness t and the antiglare height h are obtained from the height distribution function H(x).
The graph indicated by the height distribution function H(x) has a first peak P1, where the frequency sharply increases as the height on the horizontal axis increases from 0. In other words, in the antiglare layer 12, the portion having the height of the antiglare film thickness t is distributed most. Therefore, the antiglare film thickness t can be defined as the height from 0 to the first peak P1.

Also, the graph of the height distribution function H(x) has a second peak P2 corresponding to the anti-glare height h, which is higher than the first peak P1. The antiglare height h can be defined as the difference between the height of the second peak P2 and the height of the first peak P1 in the height of the horizontal axis of the height distribution function H(x).

(Calculation method of height distribution function H(x))
A method of calculating the height distribution function H(x) will be described below.
A method of calculating the height distribution function H(x) includes a measurement step and a height distribution calculation step described below.

(measurement step)
In the measurement step, a plurality of measurement samples similar to the transparent article 10 are prepared. The measurement sample is manufactured through the same manufacturing process as that of the transparent article 10 . In this embodiment, a first sample 31 shown in FIG. 3 and a second sample 32 shown in FIG. 4 are produced based on the measurement samples.

The first sample 31 and the second sample 32 are configured so that the refractive index distributions in the thickness direction are different from each other in the vicinity of the surface of the uneven structure 20 . For example, in the second sample 32 , the optical film 33 is provided on the surface of the uneven structure 20 . On the other hand, in the first sample 31, no optical film is provided on the surface of the concave-convex structure 20. FIG. Thereby, the first sample 31 and the second sample 32 have different refractive index distributions in the thickness direction near the surface of the uneven structure 20 . In order to eliminate the influence of reflection from the back surface of the measurement sample, it is preferable to subject the back surface of the measurement sample to blasting.

The optical film 33 of the second sample 32 has a single-layer or multi-layer film configuration. The optical film 33 includes, for example, a single layer or multiple layers of silicon dioxide, a single layer or multiple layers of niobium pentoxide, or the like.

Even when an optical film is provided on the surface of the antiglare layer 12 of the first sample 31, the refractive index distribution in the thickness direction can be changed from that of the first sample 31 to that of the second sample 31 by changing the film configuration of the optical film. It is possible to make it different from sample 32 .

In the measurement step, specular reflection spectra of each of the first sample 31 and the second sample 32 are measured using the measuring device 41 shown in FIG.
As shown in FIG. 5 , the measurement device 41 includes a light source 42 , a bifurcated optical fiber 43 , a collimator lens 44 and a spectroscope 45 . The light emitted from the light source 42 is introduced into the bifurcated optical fiber 43, converted into parallel light L by the collimator lens 44, and irradiated to the first sample 31 or the second sample 32 as the measurement sample. The optical axis CL of the collimator lens 44 is set perpendicular to the surface of the antiglare layer 12 of the measurement sample. Thereby, the light emitted from the collimator lens 44 vertically enters the surface of the antiglare layer 12 .

Then, only the regular reflection component of the light reflected on the surface of the antiglare layer 12 is introduced into the spectroscope 45 via the bifurcated optical fiber 43 by the collimator lens 44, and the spectroscope 45 measures the spectrum of the specular reflection component. will be For example, FIG. 6 shows a first sample specular reflection spectrum Sp1 obtained by spectrum measurement for the first sample 31. As shown in FIG. Also, for example, FIG. 7 shows a second sample specular reflection spectrum Sp2 obtained by spectrum measurement for the second sample 32 . The film configuration of the optical film 33 in the second sample 32 is desirably set so that the peak wavelengths of the first sample specular reflection spectrum Sp1 and the second sample specular reflection spectrum Sp2 are largely different. This is for calculating an accurate height distribution function H(x) in the subsequent height distribution calculation step.

(Regarding reflectance R)
Next, a method for calculating the reflectance R on the surface of the transparent article 10 on the antiglare layer 12 side will be described. The reflectance R can be calculated based on the following formula (4).

上記式（４）に示すように、反射率Ｒは、高さ分布関数Ｈ（ｘ）を重みとして、複素数振幅反射率ｒ（ｘ）を高さｘで積分することで計算される。高さｘは、厚さ方向における境界面１３から凸部２２の先端までの長さである。

As shown in the above equation (4), the reflectance R is calculated by integrating the complex amplitude reflectance r(x) over the height x with the height distribution function H(x) as weight. The height x is the length from the boundary surface 13 to the tip of the projection 22 in the thickness direction.

Equation (4) above will be described below. As shown in FIG. 8, specular reflection is considered in which parallel light irradiated onto the transparent base material 11 from the position P is reflected by the surface of the antiglare layer 12 and returns to the position P. As shown in FIG. At this time, the reflected light L1 returning to the position P has a phase difference depending on whether the parallel light is reflected by the concave portion or the convex portion of the concave-convex structure 20 . Further, when there is a refractive index difference between the transparent substrate 11 and the antiglare layer 12, the reflected light L1 reflected on the surface of the antiglare layer 12 and the boundary between the transparent substrate 11 and the antiglare layer 12 transmitted through the antiglare layer 12 Interference with the reflected light L2 reflected by the surface 13 is considered. Based on this idea, the reflected light from the transparent base material 11 is expressed as a complex amplitude reflectance r(x) in which the amplitude reflectance and the phase change are collectively expressed as a complex number. Also, assume that when the period of the uneven structure 20 is sufficiently short and the distance from the surface of the antiglare layer 12 to the position P is sufficiently long, the complex amplitude reflectance r(x) causes interference at the position P. Since the height x has a density represented by the height distribution function H(x), the reflection is obtained by integrating the complex amplitude reflectance r(x) with the height distribution function H(x) as a weight. A rate R can be calculated. By calculating the reflectance R for each wavelength based on the height distribution function H(x), the specular reflection spectrum on the surface of the transparent article 10 on the antiglare layer 12 side can be calculated.

(Height distribution calculation step)
In the height distribution calculating step, the height distribution function H(x) of the uneven structure 20 of the antiglare layer 12 is calculated based on the first sample specular reflection spectrum Sp1 and the second sample specular reflection spectrum Sp2 measured in the measuring step. Calculate Specifically, the specular reflection spectrum calculated from the reflectance R in the above formula (4) is the height distribution function H(x) that matches the first sample specular reflection spectrum Sp1 and the second sample specular reflection spectrum Sp2. find the solution. That is, in the height distribution function H(x), the proportionality constants k ₂ and k ₃ , the shift amount d, the standard deviation σ, and the gain a are changed, and the first sample specular reflection spectrum Sp1 and the second sample positive A value of each parameter that matches with each of the reflection spectra Sp2 is obtained. Thereby, the height distribution function H(x) is obtained. Then, the antiglare film thickness t and the antiglare height h are obtained from the height distribution function H(x).

(Relationship between antiglare height h and luminous reflectance)
FIG. 9 is a graph showing the relationship between the antiglare height h and the luminous reflectance in the transparent article 10. As shown in FIG.

<Luminous reflectance>
The light source is a D65 light source and a CIE 1964 colorimetric auxiliary standard observer, and the specular reflectance spectrum measured using the measuring device 41 shown in FIG. reflectance) was calculated.

As shown in FIG. 9, in the antiglare film thickness t of various dimensions, the luminous reflectance decreases as the antiglare height h increases from 110 nm in the range of 110 to 190 nm. When the antiglare height h is in the range of 120 to 150 nm, the luminous reflectance declines to a peak, and then the luminous reflectance increases as the antiglare height h increases. As shown in the figure, when the antiglare film thickness t is 30 to 70 nm, that is, in the present embodiment, the optical film thickness is 43 to 101 nm, and the antiglare height h is in the range of 110 to 180 nm, the luminous reflection rate becomes 0.06% or less. Therefore, reflection of specular reflection images on the antiglare layer 12 of the transparent article 10 is preferably suppressed. Furthermore, when the antiglare film thickness t is 30 to 70 nm, that is, the optical film thickness is 43 to 101 nm, and the antiglare height h is in the range of 120 to 160 nm, the luminous reflectance is 0.03% or less. less and more effective.

Examples 1 to 4 and Comparative Examples 1 and 2 are given below to further specifically describe the above embodiment. The present invention is not limited to Examples 1-4.

As shown in Table 3, in each of Examples 1 to 4 and Comparative Example 1, an anti-glare layer having an uneven structure was formed by spraying a liquid containing a silica component onto glass as a transparent substrate. there is In each of Examples 1 to 4 and Comparative Example 1, the antiglare film thickness t, the antiglare height h, the arithmetic mean height Sa, and the mean length RSm of the roughness curve element were set differently. Comparative Example 2 has a configuration in which the anti-glare layer is not provided on the glass as the transparent substrate.

In Table 3, the arithmetic mean height Sa is the arithmetic mean height of the uneven structure 20 of the antiglare layer 12 . The arithmetic mean height Sa can be measured according to ISO25178. When the arithmetic mean height Sa is 20 nm or more and 200 nm or less, it is possible to suitably suppress reflection of specular reflection images on the antiglare layer 12 .

In Table 3, the average length RSm of roughness curvilinear elements is the average length of the roughness curvilinear elements in the uneven structure 20 of the antiglare layer 12 . The average length RSm of roughness curve elements can be measured according to JIS B 0601 (2001). When the average length RSm of the roughness curvilinear element is 5 μm or more and 40 μm or less, it is possible to suitably suppress reflection of specular reflection images on the antiglare layer 12 .

<Luminous reflectance>
As shown in Table 3, in each of Examples 1 to 4, the luminous reflectance was 0.0300% or less, and it can be said that the reflection of the antiglare layer is sufficiently suppressed. Further, in Examples 1 to 3, the luminous reflectance was 0.0030% or less, and the reflection of the antiglare layer was further suppressed. Furthermore, in Example 1, the luminous reflectance is 0.0005%, which is the lowest among the examples.

<Clarity value>
The clarity value is the ratio of the regular reflection component to the brightness of the total reflected light obtained from the brightness distribution data of the image of the light source reflected on the surface of the antiglare layer 12 having the uneven structure 20 . This clarity value is a value indicating the degree of glare on the surface of the antiglare layer 12, and the more the glare on the surface of the antiglare layer 12 is suppressed, the smaller the clarity value. By measuring the clarity value, the reflection on the surface of the antiglare layer 12 can be evaluated quantitatively, which is similar to image recognition based on human vision. The clarity value is preferably 0.05 or less. As shown in Table 3, in each of Examples 1 to 4, the clarity value is 0.05 or less, and reflection of the antiglare layer is further suppressed. Further, in Examples 1 to 3, the clarity value is 0.03 or less, and the reflection of the antiglare layer is further suppressed. Furthermore, in Example 1, the clarity value is 0.01, which is the lowest clarity value among the examples.

<Effect of suppressing reflection of anti-glare layer>
Table 3 shows the results of visual observation and evaluation of the evaluation samples of each example. In each of Examples 1 to 4, excellent results were obtained in the effect of suppressing glare, and in particular, in Examples 1 to 3, more excellent results were obtained. On the other hand, in Comparative Examples 1 and 2, the results were inferior in the glare suppressing effect.

Effects of the present embodiment will be described.
(1) The anti-glare layer 12 has an optical film thickness of 43 nm or more and 101 nm or less at a wavelength of 550 nm of the anti-glare film thickness t, and an anti-glare height h, which is the protrusion height of the protrusions 22 of the uneven structure 20, is 110 nm or more. , and 180 nm or less. With this configuration, as shown in FIG. 9, it is possible to keep the luminous reflectance of the surface of the antiglare layer 12 small. As a result, it is possible to obtain a sufficient antireflection effect by the antiglare layer 12 while facilitating the production of the transparent article 10 by eliminating the need for an antireflection film composed of a dielectric multilayer film or the like, which is complicated to be molded.

(2) In the transparent article 10, the arithmetic mean height Sa of the concave-convex structure 20 is preferably 20 nm or more and 200 nm or less. According to this configuration, it is possible to suppress the reflection in the anti-glare layer 12 more preferably.

(3) In the transparent article 10, the average length RSm of the roughness curvilinear elements of the uneven structure 20 is preferably 5 μm or more and 40 μm or less. According to this configuration, it is possible to suppress the reflection in the anti-glare layer 12 more preferably.

(4) An antifouling layer 14 is provided on the surface of the uneven structure 20 of the antiglare layer 12 . According to this configuration, it is possible to suppress adhesion of dirt to the surface of the antiglare layer 12 by the antifouling layer 14 .

(5) The transparent article 10 does not have a dielectric multilayer film on the surface of the uneven structure 20 of the antiglare layer 12 . This configuration makes it possible to facilitate the manufacture of the transparent article 10 .

This embodiment can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
- In the transparent article 10 of the above embodiment, the refractive index of the antiglare layer 12 may be set higher than the refractive index of the transparent substrate 11 .

- In the transparent article 10 of the above embodiment, the antifouling layer 14 may be omitted.
- In the measurement step, the specular reflection spectrum of the sample may be measured by the specular reflection of light incident on the surface of the antiglare layer 12 at an oblique angle.

- Although no optical film is provided on the surface of the antiglare layer 12 in the first sample 31 of the above embodiment, the present invention is not particularly limited to this. An optical film may also be provided on the first sample 31 as long as the refractive index distribution in the thickness direction on the surface of the antiglare layer 12 is different from that of the second sample 32 .

- The embodiments and modifications disclosed this time are exemplifications in all respects, and the present invention is not limited to these exemplifications. That is, the scope of the present invention is indicated by the scope of claims, and is intended to include all changes within the meaning and scope of equivalence to the scope of claims.

DESCRIPTION OF SYMBOLS 10... Transparent article 11... Transparent base material 11a... Main surface 12... Anti-glare layer 13... Boundary surface 14... Antifouling layer 20... Concavo-convex structure 21... Concave part 22... Convex part t... Anti-glare film thickness h... Anti-glare height (projection height difference)

Claims (5)

a transparent substrate having a main surface;
an anti-glare layer provided on the main surface and having an uneven structure on the surface;
with
The refractive index of the anti-glare layer is different from the refractive index of the transparent substrate,
The anti-glare layer has an optical film thickness of 43 nm or more and 101 nm or less at a wavelength of 550 nm in the recesses of the uneven structure,
The projection height of the projections of the uneven structure is 110 nm or more and 180 nm or less.
transparent goods. The arithmetic mean height Sa of the uneven structure is 20 nm or more and 200 nm or less.
A transparent article according to claim 1 . The average length RSm of the roughness curve element of the uneven structure is 5 μm or more and 40 μm or less.
A transparent article according to claim 1 or 2. An antifouling layer is provided on the surface of the uneven structure of the antiglare layer,
4. The transparent article according to any one of claims 1-3. The surface of the uneven structure of the antiglare layer does not have a dielectric multilayer film,
A transparent article according to any one of claims 1 to 4.

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