JP2020016455A - Method of evaluating transparent article and method of manufacturing transparent article - Google Patents

Abstract

To evaluate optical characteristics of a transparent article on the basis of a three-dimensional shape of its surface.SOLUTION: On the basis of a three-dimensional shape of a surface of a transparent article, a slope distribution Slope(γ) representing a frequency per unit solid angle of a slope angle γ formed between a normal nof the surface of the transparent article and a normal nof a minute plane dS on the surface of the transparent article is obtained. A slope angle γ' of a minute plane parallel with a plane where incident light at an arbitrary incident angle and reflected light at an observation angle show relationship of regular reflection is obtained from an optional incident angle and an optional observation angle. An influence on bright-place contrast of the transparent article is evaluated on the basis of a frequency per unit solid angle of the evaluation slope angle γ' obtained from the slope distribution Slope(γ).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for evaluating a transparent article and a method for manufacturing a transparent article.

  For example, as disclosed in Patent Literature 1, from the viewpoint of improving the visibility of a display device, it has been proposed that the surface of a transparent article disposed on the display surface of the display device be an anti-glare surface. The reflected light is scattered on the anti-glare surface, so that reflection on the surface of the transparent article can be suppressed.

JP-A-9-101518

  Incidentally, one of the characteristics required for the display device is that the contrast (bright place contrast) under a bright place such as an environment where sunlight enters is high. The bright place contrast of the display device is determined from the brightness of the display, the intensity of incident light such as sunlight, which enters the display surface from the outside, and the reflectance distribution of the transparent article arranged on the display surface. In detail, the light place contrast of the display device is, as shown in the following equation, the product of the intensity of the incident light from the outside and the reflectance distribution of the transparent article arranged on the display surface, and the brightness of the display device. Can be expressed as a ratio of

Bright place contrast = luminance of display device / (intensity of incident light x reflectance distribution)
The brightness of the display device is a factor based on the display performance of the display device. The intensity of the incident light is an element based on the type of light place such as an environment where sunlight is incident and an environment where an interior light is incident. The reflectance distribution is an element based on the degree of light scattering according to the material and surface shape of the transparent article. Among the luminance of the display device, the intensity of the incident light, and the reflectance distribution, the only factor that is affected by the characteristics of the transparent article is the reflectance distribution. Therefore, when evaluating the effect of the transparent article on the light place contrast, the reflectance of the transparent article at a specific incident angle and a specific observation angle may be measured.

  As a result of earnest research, the present inventor has found that by using specific parameters based on the three-dimensional shape of the surface of a transparent article, it is possible to evaluate optical properties such as the reflectance distribution and the effect on bright place contrast of the transparent article. Was. The present invention has been made in view of such circumstances, and an object thereof is to evaluate the optical characteristics of a transparent article based on the three-dimensional shape of the surface.

  A method for evaluating a transparent article that solves the above-mentioned problem is a method for evaluating a transparent article that evaluates optical characteristics of the transparent article, and a normal line of the surface of the transparent article based on a three-dimensional shape of the surface of the transparent article. And a gradient distribution indicating a frequency of a gradient angle per unit solid angle formed by a normal angle of a minute plane on the surface of the transparent article and the normal angle, and evaluating the optical characteristics of the transparent article based on the gradient distribution.

  According to the above configuration, the optical characteristics of the transparent article can be evaluated based on the three-dimensional shape of the surface. That is, the gradient distribution obtained from the three-dimensional shape of the surface of the transparent article is a parameter highly correlated with the reflectance distribution of the transparent article. Therefore, using the gradient distribution as an index, it is possible to evaluate optical characteristics related to the reflectance distribution such as the reflectance of the transparent article and the effect on the bright place contrast of the transparent article. Further, according to the above configuration, the optical characteristics of the transparent article can be evaluated without measuring the reflectance of the transparent article.

  In the above-described method for evaluating a transparent article, the gradient angle of a minute plane parallel to a plane in which the incident light at the incident angle and the reflected light at the observation angle have a regular reflection relationship from an arbitrary incident angle and observation angle is evaluated. It is preferable that the influence on the bright place contrast of the transparent article is evaluated based on a frequency per unit solid angle of the evaluation gradient angle obtained from the gradient distribution.

  According to the above configuration, the effect on the bright place contrast of the transparent article can be evaluated from the three-dimensional shape of the surface of the transparent article. Further, the evaluation under a plurality of conditions can be easily performed as compared with the case where the evaluation is performed based on the reflectance distribution of the transparent article.

  In the method for evaluating a transparent article, a correction is performed by integrating a component of a reflectance change depending on an incident angle and a reflection angle obtained by the Fresnel equation into the gradient distribution, and based on the corrected gradient distribution, It is preferable to evaluate the reflectance distribution of the transparent article at an incident angle or a reflection angle, or the reflectance of the transparent article at an arbitrary incident angle and an arbitrary reflection angle.

According to the above configuration, the reflectance distribution of the transparent article at an arbitrary incident angle can be evaluated from the three-dimensional shape of the surface of the transparent article.
In the method for evaluating a transparent article, it is preferable that a three-dimensional shape of a surface of the transparent article is measured, and the gradient distribution is obtained based on the measured three-dimensional shape.

In the above method for evaluating a transparent article, the transparent article preferably has an anti-glare surface.
A method for manufacturing a transparent article that solves the above-mentioned problem is a method for manufacturing a transparent article having an anti-glare surface, wherein an anti-glare surface forming step of forming the anti-glare surface on a surface of a transparent substrate, and the anti-glare surface is formed. An evaluation step of evaluating the optical properties of the transparent substrate, and a pass / fail determination of determining whether or not the transparent substrate on which the anti-glare surface is formed is a non-defective transparent article based on an evaluation result of the evaluation step. And the above evaluation method is used as the evaluation step.

  According to the above configuration, in the evaluation step, the optical characteristics such as the influence on the reflectance distribution and the bright place contrast can be evaluated only by obtaining the data of the three-dimensional shape of the surface. Therefore, the operation for manufacturing a transparent article having a predetermined optical property can be simplified.

  ADVANTAGE OF THE INVENTION According to this invention, the optical characteristic of a transparent article can be evaluated based on the three-dimensional shape of the surface.

Explanatory drawing of a calculation step. FIG. 4 is an explanatory diagram of an evaluation gradient angle γ ′. FIG. 4 is an explanatory diagram of a method for measuring a reflectance distribution. FIG. 3 is an explanatory diagram showing conversion from a φ coordinate system to a φ ′ coordinate system. FIG. 4 is an explanatory diagram of the Fresnel equation. 5 is a graph in which a gradient distribution Slope (γ) of transparent articles A and D and a corrected reflectance distribution R ′ (φ ′) are superimposed. The graph which superimposedly showed the correction | amendment gradient distribution Slope '((gamma)) and the reflectance distribution R ((phi)).

[First Embodiment]
Hereinafter, a first embodiment in which the evaluation method of the present invention is embodied as a method for evaluating the effect of a transparent article on bright place contrast will be described.

First, a transparent article to be evaluated will be described.
The transparent article has a sheet shape or a plate shape having a first main surface located on the front side and a second main surface located on the back side. The transparent article is used, for example, by arranging it on a display surface of a display device. In this case, the transparent article may be a member attached on the display surface of the display device. That is, the transparent article may be a member that is later attached to the display device.

The material of the transparent article is not particularly limited. Examples of the material of the transparent article include glass and resin. The material of the transparent article is preferably glass. As the glass, for example, known glass such as non-alkali glass, borosilicate glass, aluminosilicate glass, soda lime glass, and chemically strengthened glass can be used. Among the known glasses, aluminosilicate glass is used. In particular, in terms of mass%, SiO ₂ : 50 to 80%, Al ₂ O ₃ : 5 to 25%, B ₂ O ₃ : 0 to 15%, _{Na 2 O: 1~20%, K} 2 O: it is preferable to use a chemically strengthened glass containing 0-10%.

  The transparent article preferably has a translucent anti-glare surface on the first main surface. The structure of the anti-glare surface is not particularly limited. Examples of the anti-glare surface include an anti-glare surface formed by applying a coating agent and an anti-glare surface formed by blasting or etching. Further, the transparent article may have other layers such as an antireflection layer and an antifouling layer.

  Next, an evaluation method for evaluating the effect of the transparent article on the light place contrast will be described. This evaluation method is implemented by sequentially performing a measurement step, a calculation step, and an evaluation step described below.

(Measurement step)
Using a laser microscope, the three-dimensional shape of the surface of the transparent article is measured. As a laser microscope, it is preferable to use a laser microscope (for example, VK-X250 manufactured by KEYENCE) that can measure with an XY resolution of 0.3 μm or less and a height resolution of 0.5 nm or less, since measurement with high resolution can be performed. The measurement conditions are not particularly limited, but it is preferable to set the measurement range to 200 μm or more × 200 μm or more, and the measurement point density to 12 Point / μm ² or more.

(Calculation step)
From the data of the three-dimensional shape obtained in the measurement step, a gradient distribution Slope (γ) representing the frequency per unit solid angle of the gradient angle γ of the minute plane on the surface of the transparent article is calculated. As shown in FIG. 1, the gradient angle γ is an angle between a normal line n ₀ of the surface of the transparent article and a normal line n ₁ of a minute plane on the surface of the transparent article. As shown in the following expression (1), the gradient distribution Slope (γ) is obtained by converting the distribution function ρ (γ) of the gradient angle γ into a solid angle represented by a minute area dγ of the gradient angle γ in the distribution function ρ (γ). It is obtained by dividing by dΩ (dγ).

(Evaluation step)
An incident angle and an observation angle of light serving as evaluation conditions are set based on the use conditions of the transparent article to be evaluated. For example, in the case of a transparent article used for the display surface of a car navigation device, the angle at which sunlight enters the navigation device from the rear window is defined as an incident angle θA, and the angle at which the user seated in the driver's seat overlaps the line of sight of the navigation device. Is set as the observation angle φA and the evaluation condition is set.

  Next, an evaluation gradient angle γ ′ is obtained from the incident angle θA and the observation angle φA using the following equation (2). Then, the gradient amount Slope (γ ′) when “γ = γ ′” is obtained from the gradient distribution Slope (γ).

The gradient Slope (γ ′) is a quantitative index indicating the magnitude of the effect on the bright place contrast of the transparent article at the incident angle θA and the observation angle φA. Therefore, based on the value of the slope amount Slope (γ ′) of the transparent article, it is possible to evaluate the effect of the transparent article on the bright place contrast under the evaluation conditions. Note that the larger the slope amount Slope (γ ′), the greater the effect on the bright place contrast of the transparent article.

Here, as shown in FIG. 2, the evaluation gradient angle γ ′ includes a line L that bisects the incident light at the incident angle θA and the reflected light at the reflection angle φA with respect to the transparent article 10, This is the angle between the normal line n ₀ and the normal line n ₁ corresponds to the gradient angle of the minute plane that coincides with the line L. Therefore, the slope amount Slope (γ ′) means the amount of a minute plane parallel to the plane where the incident light at the incident angle θA and the reflected light at the observation angle φA have a regular reflection relationship on the surface of the transparent article. . When the slope (Slope (γ ′)) is large, there are many minute planes parallel to the plane in which the incident light at the incident angle θA and the reflected light at the observation angle φA have a regular reflection relationship. It is considered that the reflected light in the direction of the angle φA becomes strong, and the influence on the bright place contrast is increased.

  As shown in FIG. 6, for two types of transparent articles having different surface shapes, the reflectance distribution was measured using a goniophotometer and compared with the gradient distribution Slope (γ). The gradient distribution Slope (γ) matched the specific reflectance distribution at a high level. This result also indicates that the gradient distribution Slope (γ) has a high correlation with the reflectance distribution, and is effective as a parameter for evaluating the effect on the bright place contrast.

  In addition, the reflectance distribution shown in FIG. 6 is based on the reflectance change component obtained by the Fresnel equation with respect to the reflectance distribution measured under the measurement conditions in which the incident angle is fixed and the reflection angle is set in a predetermined range. It is a corrected reflectance distribution after performing correction to remove. The corrected reflectance distribution can be obtained by the following method.

As shown in FIG. 3, in a state where the incident angle θ from the light source to the transparent article 10 to be evaluated is fixed to the specified value θA, using the goniophotometer, the transparent article 10 having the reflection angle φ as a variable is used. The reflectance distribution R _θA (φ) is measured. More specifically, the light source 21 of the goniophotometer is fixed at a position where the incident angle θA with respect to the transparent article 10, and the incident light (visible light) from the light source 21 is incident on the transparent article 10. Then, the reflectance at each reflection angle φ is measured while moving the position of the light receiving section 22 of the goniophotometer so as to receive the reflected light within a predetermined angle range.

Based on the following equation (3), reflectance distribution obtained by the measuring step R _{.theta.A (phi)} of the angular coordinate system phi reflectance was converted from the coordinate system in the? 'Coordinate system distribution R _.theta.A a _(the?') Ask. As shown in FIG. 4, the conversion angle φ ′ is a virtual transparent article 10 a inclined so that a line L bisecting the incident light and the reflected light at the reflection angle φ becomes a normal to the incident point P; This is the angle difference with the article 10.

Next, the energy reflectance F at the conversion angle φ ′ is determined based on the Fresnel equation. As shown in the following formula (4), the energy reflectance F is amplitude reflectance r _p of p-wave in the incident _light, the amplitude reflectance r _S of s-wave in the incident _light, the ratio of p-wave in the incident light p, the incident It can be obtained from the ratio s of the s-wave in the light.

Then, the amplitude reflectance r _p of the p-wave obtained based on the Fresnel's equation shown in the following (5) and the amplitude reflectance r _S of the s-wave obtained based on the Fresnel's equation shown in the following (6) are obtained. Substitute into equation (4).

As shown in FIG. 5, in the above formulas (5) and (6), “α” indicates an incident angle of incident light, and “β” indicates a refraction angle of refracted light. n _A is the refractive index of the medium A (air layer), _{n B} is the refractive index of the medium B (transparent article 10).

Here, the incident angle α of the incident light is defined as a conversion angle φ ′. The following equation (8) obtained by converting the following equation (7) based on Snell's law is substituted for the refraction angle β of the refracted light. Known constants obtained from the measurement conditions of the measurement step are substituted for the refractive index n _A , the refractive index n _B , the ratio p of the p-wave in the incident light, and the ratio s of the s-wave in the incident light. Thus, the energy reflectance F can be represented as a function F (φ ′) with the conversion angle φ ′ as a variable.

Next, as shown in the following equation (9), the corrected reflectance distribution R ′ (φ ′) is obtained by dividing the reflectance distribution R _θA (φ ′) by the energy reflectance F (φ ′).

The function F (φ ′) having the conversion angle φ ′ as a variable corresponds to a component of the reflectance change depending on the incident angle of the transparent article 10 included in the reflectance distribution R _θA (φ ′). Therefore, the corrected reflectance distribution R ′ (φ ′) obtained by dividing the reflectance distribution R _θA (φ ′) by the energy reflectance F (φ ′) is a reflectance that is generalized with respect to the incident angle and the reflection angle. Distribution. Regarding a technique of using the corrected reflectance distribution R ′ (φ ′) as a quantitative index indicating the magnitude of the effect on the bright place contrast of a transparent article, the present applicant has disclosed in Japanese Patent Application No. 2018-072663. Disclosed.

Next, effects of the present embodiment will be described.
(1) A gradient distribution indicating a frequency per unit solid angle of a gradient angle γ formed by a normal to the surface of the transparent article and a normal to a minute plane on the surface of the transparent article based on the three-dimensional shape of the surface of the transparent article. Slope (γ) is obtained. From the arbitrary incident angle θA and the observation angle φA, a gradient angle γ ′ of a minute plane parallel to a plane in which the incident light at the incident angle θA and the reflected light at the observation angle φA have a regular reflection relationship is obtained. Based on the frequency per unit solid angle of the evaluation gradient angle γ ′ obtained from the gradient distribution Slope (γ), the effect on the bright place contrast of the transparent article is evaluated.

  According to the above configuration, the effect on the bright place contrast of the transparent article can be evaluated from the three-dimensional shape of the surface of the transparent article. That is, the slope amount Slope (γ ′) is a quantitative index indicating the magnitude of the effect on the bright place contrast of the transparent article at the incident angle θA and the observation angle φA. Therefore, based on the value of the slope amount Slope (γ ′) of the transparent article, it is possible to evaluate the effect of the transparent article on the bright place contrast under the evaluation conditions.

(2) The effect of the transparent article on the bright place contrast can be evaluated without measuring the reflectance of the transparent article.
(3) Compared to the case where the evaluation is performed based on the reflectance distribution of the transparent article, the evaluation under a plurality of conditions can be easily performed.

  As a method of evaluating the effect of the transparent article on the light place contrast, as described in the subject section, the reflectance of the transparent article at a specific incident angle and observation angle serving as evaluation conditions is measured, and the obtained reflectance is obtained. Based on the evaluation method. In this case, when changing the evaluation condition, it is necessary to perform the operation of measuring the reflectance again under the changed evaluation condition. On the other hand, in the case of the evaluation method having the above configuration, when the evaluation condition is changed, an evaluation gradient angle corresponding to the changed evaluation condition may be obtained, and the evaluation gradient angle may be applied to the gradient distribution. Need not be done again.

[Second embodiment]
Hereinafter, a description will be given of a second embodiment in which the evaluation method of the present invention is embodied in a method of evaluating the reflectance distribution of a transparent article. The evaluation method of the second embodiment is a method of evaluating the reflectance distribution (reflectance distribution with the reflection angle as a variable) of the transparent article at an arbitrary incident angle based on the three-dimensional shape of the surface of the transparent article. This evaluation method is implemented by sequentially performing a measurement step, a calculation step, and an evaluation step described below.

(Measurement step)
In the same manner as in the measurement step of the first embodiment, data on the three-dimensional shape of the transparent article is obtained.

(Calculation step)
In a manner similar to the calculation step of the first embodiment, the gradient distribution Slope (γ) of the transparent article is calculated.

  Next, based on the Fresnel equation, the energy reflectance F is calculated using the above equations (4) to (8) as components of the reflectance change depending on the incident angle and the reflection angle obtained by the Fresnel equation. Find the function F (φ ′). Then, as shown in the following equation (10), the energy gradient F (φ ′) is integrated with the gradient distribution Slope (γ) as “γ = φ ′”, thereby obtaining the corrected gradient distribution Slope ′ (γ). Ask.

(Evaluation step)
An incident angle θA of light serving as an evaluation condition is set. Based on the above equation (3), the coordinate system of the corrected gradient distribution Slope ′ (φ ′) obtained in the measurement step is converted from the φ ′ coordinate system to the φ coordinate system, and the corrected gradient distribution Slope at the incident angle θA is obtained. '(Φ) is obtained.

  FIG. 7 shows that the corrected gradient distribution Slope ′ (φ) obtained from the three-dimensional shape of the same transparent article and the reflectance distribution R (φ) measured by a goniophotometer with the incident angle fixed to θA. FIG. As shown in FIG. 7, the corrected gradient distribution Slope '(φ) matches the measured reflectance distribution R (φ) at a high level. Therefore, the corrected gradient distribution Slope '(φ) can be regarded as a parameter corresponding to the reflectance distribution R (φ) when the incident angle is fixed to θA. Therefore, the reflectance distribution of the transparent article at an arbitrary incident angle can be evaluated by using the corrected gradient distribution Slope '(φ).

Next, effects of the present embodiment will be described.
(4) Gradient distribution indicating the frequency per unit solid angle of the gradient angle γ formed by the normal of the surface of the transparent article and the normal of the minute plane on the surface of the transparent article based on the three-dimensional shape of the surface of the transparent article Slope (γ) is obtained. Correction is performed to integrate the component of the change in the reflectance depending on the incident angle θ and the reflection angle φ obtained by the Fresnel equation into the gradient distribution Slope (γ). The reflectance distribution of the transparent article at an arbitrary incident angle θA is evaluated based on the corrected gradient distribution Slope ′ (φ).

  According to the above configuration, the reflectance distribution of the transparent article at an arbitrary incident angle θA can be evaluated from the three-dimensional shape of the surface of the transparent article. That is, since the corrected gradient distribution Slope '(φ) coincides with the reflectance distribution R (φ) at a high level, the corrected gradient distribution Slope' (φ) is regarded as the reflectance distribution R (φ), and the transparent article The reflectance distribution can be evaluated.

(5) The reflectance distribution of the transparent article can be evaluated without measuring the reflectance of the transparent article.
Each of the above embodiments can be modified and implemented as follows. The above embodiments and the following modified examples can be implemented in combination with each other within a technically consistent range.

  In the above embodiment, the three-dimensional shape of the surface of the transparent article is actually measured, and the gradient distribution Slope (γ) is obtained based on the measurement data of the three-dimensional shape. The gradient distribution Slope (γ) may be obtained based on the design data. In the case where the gradient distribution Slope (γ) is obtained based on the design data, the optical characteristics of the transparent article such as the influence on the bright place contrast and the reflectance distribution may be evaluated in the design stage before the production of the transparent article. Good.

In the above-described method for evaluating a transparent article, the measurement step can be omitted when the three-dimensional shape of the surface of the transparent article is known or when design data of the three-dimensional shape is used.
-With respect to the second embodiment, a method of evaluating the reflectance distribution of a transparent article at an arbitrary reflection angle (a reflectance distribution with the incident angle as a variable) may be used. In this case, a light reflection angle φA that is an evaluation condition is set. Then, based on the above equation (3), the coordinate system of the correction gradient distribution Slope ′ (φ ′) obtained in the measurement step is converted from the φ ′ coordinate system to the θ coordinate system, and the correction gradient at the reflection angle φA is converted. The distribution Slope '(θ) is obtained.

  -Regarding 2nd Embodiment, it is good also as a method of evaluating the reflectance of the transparent article in arbitrary incident angles and reflection angles. In this case, an incident angle θA and a reflection angle φA of light serving as evaluation conditions are set. Then, the conversion angle φ′A at the incident angle θA and the reflection angle φA is obtained based on the above equation (3). Based on the above equation (10), the correction gradient amount Slope '(φ'A) in the case of “φ ′ = φ′A” is obtained, and this value is determined by the reflection of the transparent article at the incident angle θA and the reflection angle φA. Consider the rate.

  -The above-described method for evaluating a transparent article can also be applied to a method for producing a transparent article having an anti-glare surface. For example, an anti-glare surface is formed on the surface of a sheet-shaped or plate-shaped transparent substrate made of glass or resin (anti-glare surface forming step). The method for forming the anti-glare surface is not particularly limited, and for example, a known forming method such as a process of applying a coating agent, a blast process, and an etching process can be used. Then, using the above-described evaluation method, the effect of the transparent substrate on which the antiglare surface is formed on the bright place contrast and the optical characteristics such as the reflectance distribution are evaluated (evaluation step). Then, based on the evaluation result, it is determined whether or not the transparent substrate on which the antiglare surface is formed is a non-defective transparent article (pass / fail determination step).

Hereinafter, the embodiment will be described more specifically with reference to examples. Note that the present invention is not limited to these.
<Test 1>
Six types of transparent articles A to F having different surface shapes are prepared, and based on the evaluation method of the first embodiment (hereinafter, referred to as a first evaluation method), the contrast of the bright places of the transparent articles A to F is improved. The effect was evaluated. Further, sensory evaluation based on human vision was performed for the light place contrast of the display device to which the transparent articles A to F were attached, and the result of the sensory evaluation was compared with the evaluation result based on the first evaluation method.

(Transparent articles A to C)
An anti-glare surface made of SiO ₂ is formed on the surface of a sheet-shaped glass substrate (T2X-1 manufactured by Nippon Electric Glass Co., Ltd.) with a thickness of 1 mm by spray coating using a spray coating apparatus. Three types of transparent articles A to C having different shapes were produced. As the coating agent, a coating agent prepared by dissolving a precursor (tetraethoxysilane) of an anti-glare film in a liquid medium containing water was used. The transparent articles A to C have different spray times, firing temperatures, and firing times in the manufacturing process.

(Transparent articles DF)
Three types of glass articles having antiglare surfaces formed by an etching method and having different surface shapes were used as transparent articles D to F, respectively.

(Evaluation by the first evaluation method)
Using a laser microscope capable of measuring XY resolution of 0.3 μm or less and height resolution of 0.5 nm or less, the three-dimensional shapes of the surfaces (anti-glare surfaces) of the transparent articles A to F were measured under the following measurement conditions. Based on the obtained data of the three-dimensional shape, the gradient distribution Slope (γ) shown in the above equation (1) was obtained.

Measurement range: 287 μm × 215 μm
Number of measurement points: 1024 x 768
Measurement point density: 12.7 Point / μm ²
Next, from the incident angle θA and the observation angle φA under the evaluation conditions, the evaluation gradient angle γ ′ was obtained using the above equation (2). The evaluation condition is that the first evaluation condition is an incident angle of 60 ° and the observation angle is 20 °, and the second evaluation condition is an incident angle of 60 ° and the observation angle is 30 °. The evaluation gradient angle γ ′ is 20 ° in the case of the first evaluation condition, and is 15 ° in the case of the first evaluation condition. Then, the logarithmic value (common logarithmic value) of the value in the case of the evaluation gradient angle γ ′ was obtained from the gradient distribution Slope (γ). The results are shown in the “logSlope” column of Tables 1 and 2.

(sensory evaluation)
Each transparent article was placed on the display surface of a display device (Smartphone: H1512 manufactured by Huawei) with the side on which the anti-glare surface was formed facing upward. In a state where sunlight is incident on the display surface of the display device from a direction at an incident angle of 60 °, 10 panelists observe images on the display device from a direction at an observation angle of 20 ° to remove white blur. They were asked if they felt it. The results are shown in the column of "Sensory evaluation" in Table 1. Further, in a state where sunlight is incident on the display surface of the display device from a direction at an incident angle of 60 °, each panelist observes an image of the display device from a direction at an observation angle of 30 ° to remove white blur. They were asked if they felt it. The results are shown in the column of "Sensory evaluation" in Table 2. In the “Sensory evaluation” column, “〇” indicates that the number of persons who evaluated white blurring was 1 or less, “△” indicates 2 to 3 persons, and “×” indicates 4 or more persons. Is shown.

As shown in Table 1 and Table 2, the magnitude relationship between the numerical values of the gradient distributions Slope (γ) in the transparent articles A to F was consistent with the result of the sensory evaluation under both the first evaluation condition and the second evaluation condition. . From these results, by using the gradient distribution Slope (γ) obtained from the three-dimensional shape of the transparent article, it is possible to improve the bright place contrast of the transparent article at any incident angle and observation angle without measuring the reflectance distribution. It can be seen that the influence can be quantitatively evaluated.

<Test 2>
For the transparent article A, the slope distribution Slope (γ) determined from the three-dimensional shape and the corrected reflectance distribution R ′ (φ ′) determined from the actually measured reflectance distribution were compared.

  Using a goniophotometer capable of measuring with an angular resolution of 0.5 ° or less, light from a light source is incident on the surface (anti-glare surface) of the transparent article A under the following measurement conditions, and the reflection of the transparent article A is performed. The rate distribution R (φ) was measured.

Light source: 520 nm wavelength, s-wave polarized laser light Incident angle: 40 °
Reflection angle range (measurement range): -90 ° to 90 °
Next, using the above equations (3) to (8), the reflectance distribution R (φ) is corrected to remove the component of the reflectance change depending on the incident angle obtained by the Fresnel equation, The corrected reflectance distribution R ′ (φ ′) was obtained. Note that the incident angle θA "40 °", the medium A (air layer) "1.00" the refractive index _{n A} of "1.45" the refractive index _{n B} of the medium B (glass layer), the incident light The ratio p of the p-wave was “0”, and the ratio s of the s-wave in the incident light was “1”. In addition, the corrected reflectance distribution R ′ (φ ′) was obtained for the transparent article D in the same manner.

  FIG. 6 is a graph in which the gradient distribution Slope (γ) of the transparent articles A and D and the corrected reflectance distribution R ′ (φ ′) are superimposed. As shown in FIG. 6, the gradient distribution Slope (γ) coincided with the corrected reflectance distribution R ′ (φ ′) at a high level.

<Test 3>
For the transparent article A, the corrected gradient distribution Slope ′ (γ) obtained from the three-dimensional shape was compared with the actually measured reflectance distribution.

Using the above equations (3) to (8), a correction for integrating the component of the reflectance change depending on the incident angle obtained by the Fresnel equation with respect to the gradient distribution Slope (γ) obtained in the test 1 is performed. The correction gradient distribution Slope '(φ) at an incident angle of 40 ° was obtained. Note that the incident angle θA "40 °", the medium A (air layer) "1.00" the refractive index _{n A} of "1.45" the refractive index _{n B} of the medium B (glass layer), the incident light The ratio p of the p-wave was “0”, and the ratio s of the s-wave in the incident light was “1”.

  Next, using a goniophotometer capable of measuring at an angular resolution of 0.5 ° or less, light from a light source is incident on the surface (anti-glare surface) of the transparent article A under the following measurement conditions, The reflectance distribution R (φ) of A was measured.

Light source: 520 nm wavelength, s-wave polarized laser light Incident angle: 40 °
Reflection angle range (measurement range): -90 ° to 90 °
FIG. 7 is a graph in which the corrected gradient distribution Slope '(φ) and the reflectance distribution R (φ) are superimposed. As shown in FIG. 7, the corrected gradient distribution Slope ′ (φ) coincided with the reflectance distribution R (φ) at a high level. From this result, the corrected gradient distribution Slope ′ (φ) can be regarded as a parameter corresponding to the reflectance distribution R (φ). By using the corrected gradient distribution Slope ′ (φ), the reflectance distribution can be calculated. It can be seen that the reflectance distribution of the transparent article at any incident angle can be evaluated without measurement.

10: transparent article, 10a: virtual transparent article, 21: light source, 22: light receiving section.

Claims (6)

A method for evaluating a transparent article for evaluating the optical properties of the transparent article,
On the basis of the three-dimensional shape of the surface of the transparent article, a gradient distribution representing a frequency per unit solid angle of a gradient angle formed by a normal to the surface of the transparent article and a normal to a minute plane on the surface of the transparent article is defined. Asked,
A method for evaluating a transparent article, comprising: evaluating an optical property of the transparent article based on the gradient distribution. From any incident angle and observation angle, the incident angle of the incident angle and the reflected light of the observation angle are obtained as the evaluation gradient angle of a minute plane parallel to a plane having a regular reflection relationship.
The method for evaluating a transparent article according to claim 1, wherein an effect of the transparent article on a light place contrast is evaluated based on a frequency of the evaluation gradient angle per unit solid angle obtained from the gradient distribution. . Correction to integrate the component of the reflectance change depending on the incident angle and the reflection angle obtained by the Fresnel equation into the gradient distribution,
Based on the corrected gradient distribution, the reflectance distribution of the transparent article at any incident angle or reflection angle, or the reflectance of the transparent article at any incident angle and reflection angle is evaluated. Item 4. The method for evaluating a transparent article according to Item 1.   The method for evaluating a transparent article according to any one of claims 1 to 3, wherein a three-dimensional shape of a surface of the transparent article is measured, and the gradient distribution is obtained based on the measured three-dimensional shape. .   The method for evaluating a transparent article according to claim 1, wherein the transparent article has an anti-glare surface. A method for producing a transparent article having an anti-glare surface,
An anti-glare surface forming step of forming the anti-glare surface on the surface of the transparent substrate,
An evaluation step of evaluating the optical characteristics of the transparent substrate on which the anti-glare surface is formed,
Based on the evaluation result of the evaluation step, a pass / fail determination step of determining whether the transparent substrate on which the anti-glare surface is formed is a non-defective transparent article,
A method for producing a transparent article, comprising using the method for evaluating a transparent article according to any one of claims 1 to 4 as the evaluation step.