CN110057547A - The method for evaluating the optical characteristics of transparent base - Google Patents

Abstract

A method of the optical characteristics of evaluation transparent base, wherein sequence differently has following steps: the step of holding the anti-glare index value R for the quantification of transparent base for having carried out anti-dazzle light processing；And the step of holding the dazzles target value G of quantification of the transparent base.

Description

Method for evaluating the optical properties of transparent substrates

This application is a divisional application of the application filed on November 11, 2016 with the application number of 201580024709.8 and the invention title is "Method for Evaluating Optical Properties of Transparent Substrate and Transparent Substrate".

technical field

The present invention relates to methods for evaluating the optical properties of transparent substrates.

Background technique

Generally, in a display device such as an LCD (Liquid Crystal Display) device having pixels, in order to protect the display device, a protective cover made of a transparent substrate is disposed.

However, when such a transparent substrate is provided on the display device, when the display image of the display device is observed through the transparent substrate, there are often cases where objects placed in the surrounding area are reflected. When such reflection occurs on the transparent substrate, it is difficult for the viewer of the displayed image to observe the displayed image, and an uncomfortable impression is received.

Therefore, in order to suppress such reflection, an anti-glare treatment may be applied to the surface of the transparent substrate.

In addition, Patent Document 1 shows a method of evaluating reflection on a display device using a special device.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2007-147343

SUMMARY OF THE INVENTION

The problem to be solved by the invention

As described above, in order to suppress the reflection of ambient light, the transparent substrate is often subjected to anti-glare treatment.

However, in an actual transparent substrate, in addition to the effect of suppressing reflection of ambient light, it may be desirable to simultaneously grasp properties such as anti-glare properties and glare.

However, a method for evaluating both the anti-glare property and the glare of a transparent substrate has not been known until now. In particular, regarding the glare of a transparent substrate, it is difficult to say that the evaluation method has been sufficiently established so far, and there is a problem that it is difficult to quantitatively evaluate itself.

In addition, as a glare evaluation apparatus of a transparent substrate, the SMS-1000 apparatus (made by Display-Messtechnik & Systeme Co., Ltd.) has attracted attention recently. In this SMS-1000 device, the glare of the transparent substrate can be evaluated by analyzing the image (brightness) of a part of the transparent substrate captured by the solid-state imaging element.

However, according to the knowledge of the inventors of the present application, it has been confirmed that an appropriate measurement result of glare is often not obtained in the evaluation by the SMS-1000 device. That is, although no intentional glare was observed under visual observation, in the evaluation based on the SMS-1000 device, there were cases where it was judged that the transparent substrate exhibited significant glare and the opposite results were produced.

In this way, a technique for properly grasping both the anti-glare property and the glare of the transparent substrate is currently required.

The present invention was made in view of such a background, and an object of the present invention is to provide an evaluation method capable of appropriately evaluating both the anti-glare property and the glare of the transparent substrate after anti-glare treatment.

solutions to problems

In the present invention, there is provided a method for evaluating the optical properties of a transparent substrate, characterized in that it has the following steps in different order:

The step of obtaining a quantitative anti-glare index value of a transparent substrate, the transparent substrate having a first surface and a second surface, and the first surface is anti-glare treated; and

the step of obtaining the quantitative glare index value of the transparent substrate,

The quantitative anti-glare index value is obtained through the following steps:

(a) irradiating the first light from the first surface side of the transparent substrate having the first and second surfaces in a direction of 20° with respect to the thickness direction of the transparent substrate, and measuring the amount of light emitted from the first surface Steps for the brightness of the reflected 20° specular light;

(b) changing the receiving angle of the reflected light reflected by the first surface in the range of -20° to +60°, and measuring the brightness of all the reflected light reflected by the first surface; and

(c) a step of estimating the anti-glare index value R according to the following formula (1),

Anti-glare index value R=

(brightness of all reflected light-brightness of regular reflection light at 20°)/(brightness of all reflected light) Formula (1),

The quantified glare index value is obtained through the following steps:

(A) the step of disposing the transparent substrate on the display device so that the second surface is positioned on the display device side;

(B) a step of photographing the transparent substrate with a solid-state imaging element and acquiring a first image with the display device turned on, and setting the distance between the solid-state imaging element and the transparent substrate to be d. When the focal length of the solid-state imaging element is set to f, the distance index r (=d/f) during shooting is 8 or more;

(C) the step of forming a first brightness distribution according to the obtained first image;

(D) the step of moving the transparent substrate in a direction substantially parallel to the second surface to move the transparent substrate relative to the display device;

(E) repeating the steps (B) and (C), and forming a second luminance distribution according to the acquired second image;

(F) the step of obtaining the difference luminance distribution ΔS according to the difference between the first luminance distribution and the second luminance distribution;

(G) The step of estimating the average luminance distribution ΔS _ave and the standard deviation σ from the differential luminance distribution ΔS, and obtaining the output value A according to the following formula (2),

Output value A = standard deviation σ/average brightness distribution ΔS _ave formula (2)

(H) The steps of (A) to (G) are performed on the transparent substrate after the anti-glare treatment for reference, and the step of obtaining the reference output value Q instead of the output value A, and the step (H) is performed in Steps performed before or in parallel with the steps of (A) to (G); and

(1) The step of obtaining the glare index value G according to the following formula (3),

Glare index value G=(output value A)/(refer to output value Q) Formula (3).

In addition, in the present invention, there is provided a transparent substrate having first and second surfaces, and the first surface is anti-glare treated, characterized in that:

When evaluated by the aforementioned method of the present invention,

The anti-glare index value R is 0.4 or more,

The glare index value G is 0.6 or less.

Invention effect

In the present invention, it is possible to provide an evaluation method which can appropriately evaluate both the anti-glare property and the glare of the transparent substrate after the anti-glare treatment.

Description of drawings

FIG. 1 is a diagram schematically showing a flow of a method for evaluating the anti-glare property of a transparent substrate according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing an example of a measuring device used for obtaining an anti-glare index value.

3 is a diagram schematically showing a flow of a method for evaluating glare of a transparent substrate according to an embodiment of the present invention.

4 is a diagram schematically showing a first image obtained in a step of a method for evaluating glare of a transparent substrate.

5 is a diagram schematically showing a first luminance distribution obtained in a step of a method for evaluating glare of a transparent substrate.

6 is a graph plotting an example of the relationship between the anti-glare index value R (horizontal axis) and the glare index value G (vertical axis) obtained in various transparent substrates.

FIG. 7 is a diagram schematically showing a transparent substrate according to an embodiment of the present invention.

8 is a graph showing an example of the relationship between the level of anti-glare property (vertical axis) and the anti-glare property index value R (horizontal axis) obtained in each transparent substrate.

9 is a graph showing an example of the relationship between the glare index value G (vertical axis) obtained in each transparent substrate and the level of glare by visual observation (horizontal axis).

Detailed ways

Hereinafter, the present invention will be described in detail.

As described above, in the transparent substrate after the anti-glare treatment, it is sometimes desirable to grasp the two characteristics of anti-glare property and glare. However, at present, there has hardly been seen a method capable of objectively evaluating both the anti-glare property and the glare of a transparent substrate.

In particular, there are various methods for applying an anti-glare treatment to a transparent substrate, and thus the surface of the transparent substrate after the anti-glare treatment also has various forms. It is extremely difficult to equally evaluate the anti-glare properties and glare of such transparent substrates having various surfaces with the same index.

For example, recently, the SMS-1000 device has attracted attention as a glare evaluation device for a transparent substrate. However, according to the knowledge of the inventors of the present application, it has been confirmed that in the evaluation by the SMS-1000 device, an appropriate measurement result of glare is often not obtained. That is, even if a transparent substrate with no intentional glare is observed by visual observation, in the evaluation based on the SMS-1000 device, it may be judged that the transparent substrate exhibits large glare, or the opposite result may occur. .

In this way, even if only focusing on the glare of the transparent substrate, it is difficult to say that a sufficiently effective measurement method has been established. In addition, in reality, there are hardly any evaluation methods focusing on both the anti-glare property and the glare of the transparent substrate.

On the other hand, in the present invention, there is provided a method for evaluating the optical properties of a transparent substrate, characterized in that it has the following steps in different order:

The step of obtaining a quantitative anti-glare index value of a transparent substrate, the transparent substrate having a first surface and a second surface, and the first surface is anti-glare treated; and

the step of obtaining the quantitative glare index value of the transparent substrate,

The quantitative anti-glare index value is obtained through the following steps:

(a) irradiating the first light from the first surface side of the transparent substrate having the first and second surfaces in a direction of 20° with respect to the thickness direction of the transparent substrate, and measuring the amount of light emitted from the first surface Steps for the brightness of the reflected 20° specular light;

(b) changing the receiving angle of the reflected light reflected by the first surface in the range of -20° to +60°, and measuring the brightness of all the reflected light reflected by the first surface; and

(c) a step of estimating the anti-glare index value R according to the following formula (1),

Anti-glare index value R=

(brightness of all reflected light-brightness of regular reflection light at 20°)/(brightness of all reflected light) Formula (1),

The quantified glare index value is obtained through the following steps:

(A) the step of disposing the transparent substrate on the display device so that the second surface is positioned on the display device side;

(B) a step of photographing the transparent substrate with a solid-state imaging element and acquiring a first image with the display device turned on, and setting the distance between the solid-state imaging element and the transparent substrate to be d. When the focal length of the solid-state imaging element is set to f, the distance index r (=d/f) during shooting is 8 or more;

(C) the step of forming a first brightness distribution according to the obtained first image;

(D) the step of moving the transparent substrate in a direction substantially parallel to the second surface to move the transparent substrate relative to the display device;

(E) repeating the steps (B) and (C), and forming a second luminance distribution according to the acquired second image;

(F) the step of obtaining the difference luminance distribution ΔS according to the difference between the first luminance distribution and the second luminance distribution;

(G) The step of estimating the average luminance distribution ΔS _ave and the standard deviation σ from the differential luminance distribution ΔS, and obtaining the output value A according to the following formula (2),

Output value A = standard deviation σ/average brightness distribution ΔS _ave formula (2)

(H) The steps of (A) to (G) are performed on the transparent substrate after the anti-glare treatment for reference, and the step of obtaining the reference output value Q instead of the output value A, and the step (H) is performed in Steps performed before or in parallel with the steps of (A) to (G); and

(1) The step of obtaining the glare index value G according to the following formula (3),

Glare index value G=(output value A)/(refer to output value Q) Formula (3).

In the method for evaluating the optical properties of the transparent substrate of the present invention, as shown in detail below, regardless of the method of anti-glare treatment, both the anti-glare property and the glare of the transparent substrate after the anti-glare treatment can be appropriately evaluated square.

In addition, in the method of the present invention, the numerical value is used as the anti-glare property and the glare of the transparent substrate. Therefore, regarding the anti-glare property and glare, the above-mentioned optical properties can be objectively and quantitatively judged irrespective of the subjectivity or prejudice of the observer.

(Regarding one embodiment of the method for evaluating the optical properties of the transparent substrate of the present invention)

Next, an embodiment of a method for evaluating the anti-glare property and the glare of a transparent substrate, which can be used in the method of the present invention, will be described with reference to the drawings.

(Anti-glare property evaluation method)

FIG. 1 schematically shows a flow of a method for evaluating the anti-glare property of a transparent substrate according to an embodiment of the present invention.

As shown in FIG. 1 , the method for evaluating the anti-glare property of a transparent substrate (hereinafter, also referred to as "the first method") includes the following steps:

(a) From the first surface side of the transparent substrate having the first and second surfaces, the first light is irradiated in a direction of 20° with respect to the thickness direction of the transparent substrate, and the amount of light emitted from the first surface is measured. The step of brightness of light that is specularly reflected on the surface (hereinafter, also referred to as "20° specularly reflected light") (step S110);

(b) changing the light-receiving angle of the reflected light reflected by the first surface in the range of -20° to +60°, and measuring the first light (hereinafter, also referred to as "all") reflected by the first surface the brightness of reflected light") (step S120); and

(c) A step of estimating the anti-glare index value R based on the following formula (1) (step S130 ).

Anti-glare index value R=

(Brightness of all reflected light - Brightness of regular reflected light at 20°)/(Brightness of all reflected light) Formula (1)

Hereinafter, each step will be described.

(step S110)

First, a transparent substrate having first and second surfaces opposed to each other is prepared.

The transparent substrate may be made of any material as long as it is transparent. The transparent substrate can also be eg glass or plastic or the like.

When the transparent substrate is made of glass, the composition of the glass is not particularly limited. The glass can also be, for example, soda lime glass or aluminosilicate glass.

In addition, when the transparent substrate is made of glass, chemical strengthening treatment may be performed on the first and/or second surfaces.

Here, the chemical strengthening treatment refers to immersing a glass substrate in a molten salt containing an alkali metal, and replacing an alkali metal (ion) with a small ionic radius existing on the outermost surface of the glass substrate with an alkali metal (ion) with a large ionic radius existing in the molten salt. Generic term for alkali metal (ion) technology. In the chemical strengthening treatment method, an alkali metal (ion) having an ion radius larger than the original atom is arranged on the surface of the glass substrate to be treated. Therefore, compressive stress can be applied to the surface of the glass substrate, whereby the strength (especially the rupture strength) of the glass substrate is improved.

For example, when the glass substrate contains sodium ions (Na ⁺ ), the sodium ions are replaced by potassium ions (K ⁺ ), for example, by chemical strengthening treatment. Alternatively, for example, when the glass substrate contains lithium ions (Li ⁺ ), the lithium ions may be replaced by, for example, sodium ions (Na ⁺ ) and/or potassium ions (K ⁺ ) by chemical strengthening treatment.

On the other hand, when the transparent substrate is made of plastic, the composition of the plastic is not particularly limited. The transparent substrate can also be, for example, a polycarbonate substrate.

It should be noted that, before step S110, the step of performing anti-glare treatment on the first surface of the transparent substrate is performed. The method of anti-glare treatment is not particularly limited. The anti-glare treatment may also be, for example, a sanding treatment, an etching treatment, a sandblasting treatment, a polishing treatment, a silicon coating treatment, or the like.

In the method for measuring anti-glare properties according to an embodiment of the present invention, various transparent substrates can be equally evaluated using a quantitative index value (anti-glare property index value R) indicating the anti-glare properties of the transparent substrate. Therefore, as a method of anti-glare treatment, various methods can be adopted.

The first surface of the transparent substrate after the anti-glare treatment may have a surface roughness (arithmetic mean roughness Ra) in the range of, for example, 0.05 μm to 1.0 μm.

Next, the first light was irradiated from the first surface side of the prepared transparent substrate toward a direction of 20°±0.5° with respect to the thickness direction of the transparent substrate. The first light is reflected by the first surface of the transparent substrate. Among the reflected light, the 20° regular reflection light was received, and the brightness thereof was measured as "brightness of the 20° regular reflection light".

(step S120)

Next, the receiving angle of the reflected light reflected by the first surface was changed in the range of -20° to +60°, and the same operation was performed. At this time, the luminance distribution of the first light reflected by the first surface of the transparent substrate and emitted from the first surface was measured and totaled, and the result was referred to as the "brightness of the total reflected light".

(step S130)

Next, according to the following formula (1), the anti-glare index value R is estimated:

Anti-glare index value R=

(Brightness of all reflected light - Brightness of regular reflected light at 20°)/(Brightness of all reflected light) Formula (1)

As will be described later, it was confirmed that the anti-glare property index value R correlated with the judgment result of the anti-glare property based on the visual observation of the observer, and it was confirmed that the locus close to the human vision was displayed. For example, a transparent substrate with a large anti-glare index value R (a value close to 1) has excellent anti-glare properties, whereas a transparent substrate with a small anti-glare index value R tends to have poor anti-glare properties. . Therefore, the anti-glare property index value R can be used as a quantitative index when judging the anti-glare property of the transparent substrate.

FIG. 2 schematically shows an example of a measuring device used to obtain the anti-glare index value R represented by the aforementioned formula (1).

As shown in FIG. 2 , the measurement device 300 includes a light source 350 and a detector 370 , and the transparent substrate 210 is arranged in the measurement device 300 . The transparent substrate 210 has a first surface 212 and a second surface 214 . The light source 350 emits the first light 362 toward the transparent substrate 210 . Detector 370 receives reflected light 364 reflected at first surface 212 and detects its brightness.

In addition, the transparent base 210 is arrange|positioned so that the 1st surface 212 may be located in the light source 350 and the detector 370 side. Therefore, the first light detected by the detector 370 is the reflected light 364 reflected by the transparent substrate 210 . Furthermore, when one surface of the transparent base 210 is subjected to anti-glare treatment, the anti-glare treated surface becomes the first surface 212 of the transparent base 210 . That is, in this case, the transparent substrate 210 is arranged in the measurement device 300 such that the anti-glare treated surface is located on the light source 350 and detector 370 sides.

In addition, the first light 362 is irradiated at an angle inclined by 20° with respect to the thickness direction of the transparent substrate 210 . In addition, in this application, the range of 20°±0.5° is defined as an angle of 20° in consideration of the error of the measurement device.

In such a measuring device 300 , the first light 362 is irradiated from the light source 350 toward the transparent substrate 210 , and the detector 370 arranged so that the light receiving angle φ becomes 20° is used to detect the light reflected by the first surface 212 of the transparent substrate 210 . Regular reflected light 364. Thereby, "20° regular reflection light" is detected.

Next, in the detector 370, the receiving angle ? of the measurement reflected light 364 is changed in the range of -20° to +60°, and the same operation is performed.

In addition, the luminance distribution of the reflected light 364 (referred to as total reflected light) reflected by the first surface 212 of the transparent substrate 210 is detected in the range of the light receiving angle φ=-20° to +60°, and totaled.

Here, the negative (-) of the light-receiving angle φ indicates that the light-receiving angle is on the incident light side with respect to the normal of the object surface (the first surface in the above example) to be evaluated, and the positive (+) indicates that the light-receiving angle is on the side of the incident light. When the received light angle is not on the incident light side compared to the normal to the object surface.

The anti-glare index value R of the transparent substrate 210 can be obtained by the aforementioned formula (1) from the obtained luminance of the 20° regular reflection light and the luminance of the total reflected light. In addition, such a measurement can be easily implemented by using a commercially available goniometer (variable goniophotometer).

In addition, the irradiation angle of 1st light can be suitably selected from the range of 60 degrees - 5 degrees. However, in the present application, 20° is selected as the irradiation angle of the first light from the viewpoint of the good correlation between the anti-glare property evaluation based on visual observation and the quantitative evaluation.

(About the glare index value)

FIG. 3 schematically shows a flow of a method for evaluating glare of a transparent substrate according to an embodiment of the present invention.

As shown in Figure 3, the method for evaluating the glare of a transparent substrate (hereinafter, also referred to as "the second method") includes the following steps:

(A) the step of disposing the transparent substrate having the first and second surfaces on the display device so that the second surface is located on the display device side (step S210 );

(B) a step of photographing the transparent substrate with a solid-state imaging element and acquiring a first image with the display device turned on, and setting the distance between the solid-state imaging element and the transparent substrate to be d. When the focal length of the solid-state imaging element is set to f, the distance index r (=d/f) during shooting is 8 or more (step S220);

(C) the step of forming a first luminance distribution according to the obtained first image (step S230);

(D) the step of moving the transparent substrate in a direction substantially parallel to the second surface to move the transparent substrate relative to the display device (step S240);

(E) repeating the steps (B) and (C), and forming a second luminance distribution according to the acquired second image (step S250);

(F) the step of obtaining the difference luminance distribution ΔS according to the difference between the first luminance distribution and the second luminance distribution (step S260);

(G) The step of calculating the average luminance distribution ΔS _ave and the standard deviation σ according to the differential luminance distribution ΔS, and obtaining the output value A according to the following formula (2) (step S270);

Output value A = standard deviation σ/average brightness distribution ΔS _ave formula (2)

(H) performing the steps (A) to (G) on the transparent substrate after the anti-glare treatment for the reference, and obtaining the reference output value Q instead of the output value A (step S280 );

(1) The step of obtaining the glare index value G according to the following formula (3) (step S290 ).

Glare index value G=(output value A)/(refer to output value Q) Equation (3)

Hereinafter, each step will be described in detail.

(step S210)

First, a transparent substrate having first and second surfaces opposed to each other is prepared. The first surface of the transparent substrate is anti-glare treated.

It should be noted that, the material, composition, etc. of the transparent substrate are the same as those shown in the aforementioned step S110, and therefore will not be further described here.

However, as described above, it has been difficult in the past to uniformly evaluate the glare of a transparent substrate that differs not only from a single anti-glare treatment method such as a condition change in the etching treatment, by the same index. of various surfaces, but also various surfaces that differ due to the existence of multiple anti-glare treatments.

However, in the glare evaluation method according to an embodiment of the present invention, various transparent substrates can be similarly evaluated using a quantitative index value (glare index value G) representing the glare of the transparent substrate, as will be described later. Therefore, it should be noted that the glare evaluation method according to an embodiment of the present invention is also useful as a means of selecting a treatment method for anti-glare treatment.

Next, prepare the display device. The display device is not particularly limited as long as it has a structure including pixels. The display device may be, for example, an LCD device, an OLED (Organic Light Emitting Diode) device, a PDP (Plasma Display Panel: Plasma Display) device, a flat-panel display device, or the like. The resolution of the display device is preferably, for example, 132 ppi or more, more preferably 186 ppi or more, and still more preferably 264 ppi or more.

Next, a transparent substrate is arranged on the display device. At this time, the transparent substrate is arranged on the display device so that the second surface is located on the display device side.

(step S220)

Next, with the display device turned on (ie, displaying an image), a solid-state imaging element is used to image the transparent substrate from the first surface side, and an image (first image) of the transparent substrate disposed on the display device is acquired.

The distance d between the solid-state imaging element and the transparent substrate is set to a predetermined value.

It should be noted that, in this application, the distance index r is used as an index corresponding to the distance d between the solid-state imaging element and the transparent substrate. Here, the distance index r is represented by the following formula (4) using the focal length f of the solid-state imaging element and the distance d between the solid-state imaging element and the transparent substrate:

Distance index r=(distance d between solid-state imaging element and transparent substrate)/

(The focal length f of the solid-state imaging element) Equation (4)

In addition, in this application, the distance index r is 8 or more.

This is because when the distance index r is less than 8, the distance d between the solid-state imaging element and the transparent substrate becomes small, and the shape of the first surface after the anti-glare treatment of the transparent substrate is likely to be affected. Therefore, by setting the distance index r to be 8 or more, it is possible to uniformly evaluate the performance of various methods while suppressing the influence of the difference in the morphology of the first surface due to the difference in the applied anti-glare treatment method. The glare of the transparent substrate after anti-glare treatment.

The distance index r is preferably 9 or more, and more preferably 10 or more.

The image displayed on the display device is an image of a single color (eg, green), and is preferably displayed on the entire display image surface of the display device. This is to minimize the influence of differences in observation methods due to differences in display colors.

As the solid-state imaging element, for example, a charge coupled element (CCD) and a complementary metal oxide semiconductor (CMOS) can be used. In either case, it is preferable to use a digital camera or the like having a high number of pixels.

Through this step, for example, the first image 410 schematically represented in FIG. 4 can be obtained. In the example shown in FIG. 4 , in the first image 410 , regions corresponding to 9 pixels arranged in 3 rows×3 columns in a part of the display device (hereinafter, referred to as corresponding regions 420 - 1 to 420 ) are observed. -9) Bright.

In addition, in FIG. 4, for clarity, each corresponding area|region 420-1-420-9 is shown in the state which isolate|separated sufficiently. However, it should be noted that, in an actual image, the distances between the corresponding regions 420-1 to 420-9 are narrower, and the bright parts of adjacent corresponding regions may partially overlap each other.

(step S230)

Next, image analysis is performed on the first image 410 captured in step S220 to form a first brightness distribution. The first luminance distribution is formed as a stereoscopic map on the XY plane.

FIG. 5 schematically shows an example of the first luminance distribution obtained in this step.

As shown in FIG. 5 , the first luminance distribution 430 has luminance distribution components q ₁ to q ₉ of a substantially normal distribution shape in the regions corresponding to the corresponding regions 420 - 1 to 420 - 9 of the first image 410 . More generally, the first luminance distribution 430 is represented by a set of _i multiple luminance distribution components qi (i is an integer of 2 or more).

It should be noted that, in FIG. 5 , the luminance distribution components q ₁ to q ₉ are represented two-dimensionally (ie, non-stereoscopically) in order to avoid complicated drawing.

It should be noted that, in order to improve the accuracy of the first brightness distribution 430 , the number of the first images 410 captured in step S220 may also be increased. In this step S230 , the same image analysis is performed for each first image 410 . In this case, by averaging each image analysis result, the first luminance distribution 430 with higher accuracy can be obtained.

(step S240)

Next, the transparent substrate is slid in a direction parallel to the second surface, so that the transparent substrate is relatively moved relative to the display device. The moving distance is preferably less than 10 mm, and may be, for example, several mm.

(step S250)

Next, the steps S220 to S230 are repeated. That is, while the display device is turned on, the second image is acquired by the solid-state imaging element, and the second luminance distribution is formed from the second image.

In this step, in order to increase the accuracy of the second luminance distribution, the number of second images captured by the solid-state imaging element may be increased. Then, image analysis is performed on each of the second images, and the results of each image analysis are averaged, whereby a second luminance distribution with higher accuracy can be obtained.

Thereby, the second luminance distribution represented by the set of the plurality of luminance distribution components _si (here, i is an integer of 2 or more) can be obtained. It should be noted that the luminance distribution components si are composed of the same number as the luminance distribution components qi.

(step S260)

Next, the difference luminance distribution ΔS is estimated from the difference between the first luminance distribution and the second luminance distribution. The differential luminance distribution ΔS is represented by a set of luminance distribution components t _i (here, i is an integer of 2 or more) having a substantially normal distribution shape, similarly to the first luminance distribution and the second luminance distribution.

(step S270)

Next, using the differential luminance distribution ΔS obtained in step S260, the average luminance distribution ΔS _ave and the standard deviation σ are estimated.

Here, the average luminance distribution ΔS _ave can be obtained by averaging the absolute values of the i luminance distribution components t _i included in the differential luminance distribution ΔS. Further, the standard deviation σ can be obtained from the following equation (5) using i luminance distribution components t _i included in the differential luminance distribution ΔS and the average luminance distribution ΔS _ave .

[Mathematical formula 1]

From the obtained average luminance distribution ΔSave and standard deviation σ, the output value A is estimated by the following formula (2).

Output value A = standard deviation σ/average brightness distribution ΔS _ave formula (2)

(step S280)

Next, the aforementioned steps S210 to S270 are performed using the anti-glare-treated transparent substrate for reference (standard). Thereby, the reference output value Q is obtained in place of the output value A of the above-mentioned formula (2).

Since the glare index value is represented by a ratio to the reference output value Q obtained by Equation (3) described later, the reference output value Q strongly requires measurement reproducibility and needs to be much larger than the error of each measurement. In order to easily prepare a transparent substrate after anti-glare treatment for a reference (standard) to give an appropriate reference output value Q, it is only necessary to select a flat glass that has been subjected to anti-glare treatment by frosting/etching on soda lime glass. , the 60-degree gloss value is as large as possible, and the average length RSm of the roughness curve elements is 70 μm or more and less than 120 μm, and the transparent substrate can be obtained as a commercial product.

Here, the 60-degree gloss value can be measured as specular gloss by a method in accordance with JIS-Z8741. The 60-degree gloss value is, for example, 110 or more, and more preferably 120 or more. The average length RSm of the roughness curve element can be measured by the method according to JISB0601 (2001). The average length RSm of the roughness curve elements is, for example, 70 μm or more, more preferably 80 μm or more, and less than 120 μm, preferably less than 110 μm.

In one embodiment of the present invention, VRD140 having a 60-degree gloss value of 140% and an average length RSm of surface roughness curve elements of 85 μm was selected as a transparent substrate after anti-glare treatment for a reference that satisfies the above conditions. Anti-glare treated glass (manufactured by Asahi Glass Co., Ltd.).

It should be noted that this step S280 may also be performed before performing the aforementioned steps S210 to S270 using the transparent substrate after the anti-glare treatment for evaluation. Alternatively, this step S280 may be performed in parallel with the implementation of the steps S210 to S270 of the transparent substrate after the anti-glare treatment for evaluation.

(step S290)

Next, using the output value A and the reference output value Q, the glare index value G is obtained according to the following formula (3):

Glare index value G=(output value A)/(refer to output value Q) Equation (3)

This glare index value G is related to the determination result of glare based on the visual observation of the observer, as will be described later, and it has been confirmed that a trajectory close to human vision is displayed. For example, a transparent substrate with a large glare index value G exhibits significant glare, whereas a transparent substrate with a small glare index value G tends to suppress glare. Therefore, the glare index value G can be used as a quantitative index when judging the glare of the transparent substrate.

An example of a method for evaluating the glare of a transparent substrate has been described above with reference to FIGS. 3 to 5 . However, in the present invention, the method of evaluating the glare of the transparent substrate is not limited to this.

For example, in the above-described flow, between steps S260 and S270 , a step of filtering and removing components derived from the display device may be performed based on the differential luminance distribution ΔS (step S265 ). By performing step S270 using the effective differential luminance distribution ΔS _e obtained by this operation instead of the differential luminance distribution ΔS, the accuracy of the obtained glare index value G can be further improved.

However, this step S265 may be performed when necessary, and does not necessarily have to be performed.

In addition, the method of evaluating the glare of the transparent substrate described above can be easily implemented by using, for example, an SMS-1000 apparatus (manufactured by Display-Messtechnik & Systeme).

By using the anti-glare index value R and the glare index value G as described above, the optical properties of the transparent substrate after the anti-glare treatment can be quantitatively evaluated.

(Evaluation based on 2 indicators)

Next, a method for simultaneously evaluating two optical properties of a transparent substrate and its effects will be described.

FIG. 6 shows a graph plotting the relationship between the anti-glare index value R (horizontal axis) and the glare index value G (vertical axis) obtained in the transparent substrate subjected to anti-glare treatment by various methods. An example. Here, the distance index r=10.8 at the time of shooting in the glare evaluation for this data acquisition.

In FIG. 6 , the larger the anti-glare index value R on the horizontal axis and the smaller the glare index value on the vertical axis, the more the anti-glare property of the transparent substrate is improved, and the more the glare of the transparent substrate can be suppressed.

In addition, in FIG. 6, for reference, the area|region of the ideal transparent base|substrate which has both good anti-glare property and good glare-proof property is shown by the ○ mark shown as ideal.

Here, when a candidate transparent substrate is selected from among various transparent substrates in consideration of only a single optical characteristic such as glare prevention property, the transparent substrate included in the region C indicated by the hatching in FIG. 6 is similarly selected. . That is, in such a method, a transparent substrate having poor anti-glare properties is included in the selected candidate transparent substrate. Similarly, when selecting a transparent substrate considering only the anti-glare property, the transparent substrate included in the area D indicated by the hatching in FIG. 6 is similarly selected, and the transparent substrate with poor anti-glare property is included in the selection candidate.

On the other hand, when the correlation diagram of the glare index value G and the anti-glare property R as shown in FIG. 6 is used, it is possible to select an appropriate transparent substrate in consideration of both optical properties at once. That is, in such a selection method, the transparent substrate can be appropriately selected in accordance with the purpose, application, etc., that is, the transparent substrate can be selected so as to exhibit the most favorable properties regarding the glare preventing property and the anti-glare property.

In this way, in the method according to the embodiment of the present invention, two optical properties can be quantitatively considered at one time, so that the transparent substrate can be more appropriately selected according to the purpose of use, application, and the like.

In addition, in the method of the present invention, numerical values are used as the anti-glare index value R and the glare index value G of the transparent substrate. Therefore, regarding the anti-glare property and glare, the above-mentioned optical properties can be objectively and quantitatively judged irrespective of the subjectivity or prejudice of the observer.

(Transparent base according to an embodiment of the present invention)

Next, with reference to FIG. 7, the transparent base body which concerns on one Embodiment of this invention is demonstrated.

FIG. 7 schematically shows a transparent substrate (hereinafter, simply referred to as a “transparent substrate”) 900 according to an embodiment of the present invention.

The transparent substrate 900 is made of glass. The composition of the glass is not particularly limited, and the glass may be, for example, soda lime glass or aluminosilicate glass.

The transparent substrate 900 has a first surface 902 and a second surface 904, and the first surface 902 is subjected to anti-glare treatment.

The method of anti-glare treatment is not particularly limited. The anti-glare treatment may also be, for example, a sanding treatment, an etching treatment, a sandblasting treatment, a polishing treatment, a silicon coating treatment, or the like. The first surface 902 of the transparent substrate may have a surface roughness (arithmetic mean roughness Ra) in a range of, for example, 0.05 μm to 1.0 μm.

In addition, the first surface 902 and/or the second surface 904 of the transparent substrate 900 may also be chemically strengthened.

The size and shape of the transparent substrate 900 are not particularly limited. For example, the transparent substrate 900 may also have a square shape, a rectangular shape, a circular shape, an oval shape, or the like.

It should be noted that when the transparent substrate 900 is used as the protective cover of the display device, the thickness of the transparent substrate 900 is preferably thin. For example, the thickness of the transparent substrate 900 may be in the range of 0.2 mm to 2.0 mm.

Here, the transparent substrate 900 is characterized in that the anti-glare index value R measured using the first method (step S110 to step S130 ) is 0.4 or more. Furthermore, the transparent substrate 900 is characterized in that the glare index value G, which is a distance index r=8, is measured to be 0.6 or less using the aforementioned second method (steps S210 to S290, including step S265).

The anti-glare property index value R is preferably 0.6 or more, and more preferably 0.8 or more.

In addition, the glare index value G is preferably 0.5 or less, more preferably 0.4 or less, and still more preferably 0.3 or less.

Example

Next, the results of anti-glare evaluation and glare evaluation performed using various transparent substrates will be described.

(About anti-glare evaluation)

The anti-glare property of the transparent substrate after the anti-glare treatment was performed on the first surface by various methods was evaluated by the following method.

As the anti-glare treatment, frosting treatment, etching treatment, sandblasting treatment, polishing treatment or silicon coating treatment is employed. Also, aluminosilicate glass is used for the transparent substrate.

First, each transparent substrate was visually observed from the side of the first surface (that is, the surface subjected to the anti-glare treatment), and the anti-glare property was evaluated on 12 scales from 1 to 12. In addition, the observation direction is a direction which forms 20 degrees with respect to the thickness direction of a transparent base|substrate.

Next, using a variable-angle photometer (GC5000L: manufactured by Nippon Denshoku Kogyo Co., Ltd.), the operations shown in steps S110 to S130 described above were carried out, and the anti-glare index value of each transparent substrate was estimated based on the formula (1). R.

FIG. 8 shows an example of the relationship between the anti-glare property evaluation level (vertical axis) and the anti-glare property index value R (horizontal axis) obtained in each transparent substrate.

It can be seen from Figure 8 that there is a positive correlation between the two.

The results suggest that the anti-glare index value R corresponds to the tendency of the evaluation level of the reflection image diffusivity based on the visual observation of the observer. Therefore, the anti-glare index value R can be used to determine the diffusivity of the reflected image of the transparent substrate. In other words, it can also be said that by using the anti-glare index value R, the reflection image diffusivity of the transparent substrate can be objectively and quantitatively determined.

(Evaluation on glare)

Next, the glare of the above-mentioned transparent substrate was evaluated by the following method using various transparent substrates used for the aforementioned anti-glare evaluation.

First, each transparent substrate was directly placed on a display device (iPad (registered trademark), resolution 264ppi). At this time, the transparent bases are arranged on the display device so that the first surfaces of the respective transparent bases (that is, the surfaces subjected to the anti-glare treatment) are positioned on the viewer's side. It should be noted that the image displayed from the display device was a green monochrome image, and the size of the image was 19.6 cm×14.6 cm.

Next, in this state, each transparent substrate was visually observed from the first surface side, and the glare was evaluated on 11 scales from 0 to 10. A level of 0 indicates a situation in which glare is hardly seen, and a level of 10 indicates a situation in which the glare is extremely conspicuous. Furthermore, the gradation value in between tends to increase the glare as the numerical value increases.

Next, using an SMS-1000 device (manufactured by Display-Messtechnik & Systeme), the operations shown in the aforementioned steps S210 to S290 (including step S265) were carried out, and the glare index value G of each transparent substrate was calculated according to the formula (3). . In addition, VRD140 anti-glare process glass (made by Asahi Glass Co., Ltd.) was used as the transparent base|substrate which performed the anti-glare process for a reference|standard.

As the display device, the aforementioned iPad (registered trademark) was used, and the distance d between the solid-state imaging element and the transparent substrate was set to 540 mm. If the distance d is represented by the distance index r, it corresponds to r=10.8.

FIG. 9 shows an example of the relationship between the glare index value G (vertical axis) obtained in each transparent substrate and the level of glare by visual observation (horizontal axis).

It can be seen from Figure 9 that there is a positive correlation between the two.

As a result, it is suggested that the glare index value G corresponds to the tendency of the determination result of glare based on the visual observation of the observer. Therefore, the glare index value G can be used to determine the glare of the transparent substrate. In other words, it can be said that the glare of the transparent substrate can be objectively and quantitatively determined by using the glare index value G.

In this way, it was confirmed that the anti-glare index value R and the glare index value G can be used as quantitative indexes of the anti-glare property and the glare of the transparent substrate, respectively.

Industrial Applicability

The present invention can be used for evaluation of optical properties of transparent substrates provided in various display devices such as LCD devices, OLED devices, PDP devices, and flat-panel display devices, for example.

In addition, this application claims the priority based on Japanese Patent Application No. 2014-100343 for which it applied on May 14, 2014, The whole content of this Japanese application is used for this application by reference.

Label description

210 transparent substrate

212 First surface

214 Second surface

300 Assay Devices

350 light sources

362 First Light

364 reflected light

370 detector

410 first image

420-1～420-9 Corresponding area

430 First brightness distribution

900 transparent substrate

902 first surface

904 Second surface

q _i luminance distribution components

Claims (8)

1. A method for evaluating the optical properties of a transparent substrate, characterized in that, The sequence varies with the following steps: The step of obtaining a quantitative anti-glare index value of a transparent substrate, the transparent substrate having a first surface and a second surface, and the first surface is anti-glare treated; and the step of obtaining the quantitative glare index value of the transparent substrate, The quantitative anti-glare index value is obtained through the following steps: (a) irradiating the first light from the first surface side of the transparent substrate having the first and second surfaces in a direction of 20° with respect to the thickness direction of the transparent substrate, and measuring the amount of light emitted from the first surface Steps for the brightness of the reflected 20° specular light; (b) changing the receiving angle of the reflected light reflected by the first surface in the range of -20° to +60°, and measuring the brightness of all the reflected light reflected by the first surface; and (c) a step of estimating the anti-glare index value R according to the following formula (1), Anti-glare index value R=(brightness of all reflected light-brightness of regular reflection light at 20°)/(brightness of all reflected light) Formula (1), The quantified glare index value is obtained through the following steps: (A) the step of disposing the transparent substrate on the display device so that the second surface is positioned on the display device side; (B) a step of photographing the transparent substrate with a solid-state imaging element and acquiring a first image with the display device turned on, and setting the distance between the solid-state imaging element and the transparent substrate to be d. When the focal length of the solid-state imaging element is set to f, the distance index r (=d/f) during shooting is 8 or more; (C) the step of forming a first brightness distribution according to the obtained first image; (D) the step of moving the transparent substrate in a direction substantially parallel to the second surface to move the transparent substrate relative to the display device; (E) repeating the steps (B) and (C), and forming a second luminance distribution according to the acquired second image; (F) the step of obtaining the difference luminance distribution ΔS according to the difference between the first luminance distribution and the second luminance distribution; (G) The step of estimating the average luminance distribution ΔS _ave and the standard deviation σ from the differential luminance distribution ΔS, and obtaining the output value A according to the following formula (2), Output value A = standard deviation σ/average brightness distribution ΔS _ave formula (2) (H) The steps of (A) to (G) are performed on the transparent substrate after the anti-glare treatment for reference, and the step of obtaining the reference output value Q instead of the output value A, and the step (H) is performed in Steps performed before or in parallel with the steps of (A) to (G); and (1) The step of obtaining the glare index value G according to the following formula (3), Glare index value G=(output value A)/(refer to output value Q) Formula (3). 2. The method according to claim 1, wherein Before the step (G), the following steps are carried out: a step of filtering and removing the component originating from the display device from the differential luminance distribution ΔS to obtain an effective differential luminance distribution ΔS _e , In the step (G), the effective differential luminance distribution ΔS _e is used instead of the differential luminance distribution ΔS. 3. The method according to claim 1 or 2, characterized in that, The anti-glare index value is obtained using a goniometer. 4. The method according to claim 1 or 2, characterized in that, The display device is one device selected from the group consisting of an LCD device, an OLED device, a PDP device, and a flat panel display device. 5. The method according to claim 1 or 2, characterized in that, The display device has a resolution of 132ppi or more. 6. The method according to claim 1 or 2, characterized in that, The transparent substrate consists of soda lime glass or aluminosilicate glass. 7. The method of claim 6, wherein At least one of the first and second surfaces of the transparent substrate is chemically strengthened. 8. The method according to claim 1 or 2, characterized in that, The anti-glare treatment is performed by applying at least one treatment method selected from the group consisting of sanding treatment, etching treatment, sandblasting treatment, polishing treatment and silicon coating treatment to the first surface of the transparent substrate.