阅读说明：本技术 透明基体 (Transparent substrate ) 是由 山本文 小林裕介 西条佳孝 于 2018-03-23 设计创作，主要内容包括：本发明提供一种透明基体,是具有防眩功能的透明基体,该透明基体具有第一表面和第二表面,该透明基体的通过以下方法测定的析像度指标值T、反射像扩散性指标值R和眩光指标值S分别满足T≥0.25、R≥0.8和0.75≤S≤0.95。(The invention provides a transparent substrate with an anti-dazzle function, which has a first surface and a second surface, wherein the resolution index value T, the reflection image diffusivity index value R and the glare index value S of the transparent substrate, which are measured by the following methods, respectively satisfy the condition that T is more than or equal to 0.25, R is more than or equal to 0.8 and S is more than or equal to 0.75 and less than or equal to 0.95.)

1. A transparent substrate is a transparent substrate with anti-dazzle function,

the transparent substrate has a first surface and a second surface,

the resolution index value T, the reflection image diffusivity index value R, and the glare index value S of the transparent substrate, which are measured by the following methods, satisfy each of:

T≥0.25，

r is not less than 0.8, and

0.75≤S≤0.95；

wherein the resolution index value T is obtained by:

irradiating the transparent substrate from the first surface side in a direction parallel to the thickness direction of the transparent substrate with first light, measuring the brightness of transmitted light emitted from the second surface in a direction parallel to the thickness direction of the transparent substrate, which is called 0 DEG transmitted light, and,

measuring the brightness of the transmitted light transmitted through the transparent substrate and emitted from the second surface in an angular range of-30 DEG to +30 DEG with respect to a direction parallel to the thickness direction of the transparent substrate, which is called total transmitted light,

the calculation is performed according to the following formula (1),

formula (1): resolution index value T ═ luminance of (0 ° transmitted light)/(luminance of total transmitted light);

the reflection image diffusivity index value R is obtained by:

irradiating a second light to the transparent base in a direction of +5.7 ° from a normal to the first surface from the first surface side of the transparent base,

determining a first angle α from the first surface relative to the normal₁Brightness R of regularly reflected first reflected light₁Wherein, α₁Is-5.7 ° ± 0.1 °, and

at a first angle α reflecting the first reflected light₁At 0 deg., respectively measuring a second angle α from the first surface₂Brightness R of the reflected second reflected light₂And a third angle α from the first surface₃Brightness R of the reflected third reflected light₃Wherein, α₂Is-0.5 degree +/-0.1 degree and α degree₃Is +0.5 DEG +/-0.1 DEG,

the calculation is performed according to the following formula (2),

formula (2): the reflection image diffusivity index value R is (R)₂+R₃)/(2×R₁)；

The glare index value S is obtained by:

the transparent substrate is disposed on the display surface side of the display device such that the second surface is on the display device side,

with the display device turned on, the Sparkle value of the transparent substrate was measured as the glare S using an analyzer SMS-1000_aThe same measurement was carried out using VRD140 glass, which is a glass substrate having a thickness of 1.6mm, and the obtained Sparkle value was defined as the glare S_sWhen the temperature of the water is higher than the set temperature,

the calculation is performed according to the following formula (3),

formula (3): glare index value S is 1- (S)_a/S_s)。

2. The transparent substrate according to claim 1, wherein the glare index value S is 0.8 or more.

3. The transparent substrate according to claim 2, wherein the glare index value S is 0.84 or more.

4. The transparent matrix according to claim 2 or 3, wherein the reflection image diffusivity index value R is 0.9 or more.

5. The transparent matrix according to claim 4, wherein the reflection image diffusivity index value R is 0.92 or more.

6. The transparent substrate according to any one of claims 1 to 5, wherein the pencil hardness exceeds 6H.

7. The transparent substrate according to any one of claims 1-6, wherein the haze value is less than 40.

8. The transparent substrate according to any one of claims 1 to 7, wherein the coefficient of kinetic friction is 0.4 or less.

9. The transparent substrate according to any one of claims 1 to 8, wherein the pen static friction coefficient is 0.18 to 0.3.

10. The transparent substrate according to any one of claims 1 to 9, wherein the transparent substrate is composed of glass having a thickness of 2mm or less.

11. The transparent substrate according to claim 10, wherein the transparent substrate is composed of glass having a thickness of 1.3mm or less.

Technical Field

The invention relates to a transparent substrate, in particular to a transparent substrate with an anti-dazzle function.

Background

In a display device such as a smartphone or a personal computer, a surrounding image is often reflected when a display screen is observed. If such reflection occurs on the display screen, it is difficult for the observer of the display screen to observe the displayed image or to feel an unpleasant impression.

Therefore, in order to reduce such reflection, a transparent substrate having an antiglare function is often provided on a display screen.

Disclosure of Invention

However, when a displayed image is observed through a transparent substrate having an antiglare function, the image may be unclear or a display screen may be glare (may feel flickering).

In particular, in recent years, the resolution of an image displayed on a screen has been improved in a display device, and the problems of such unsharpness and glare of the image are expected to become more significant in the future.

The present invention has been made in view of such a background, and an object of the present invention is to provide a transparent substrate capable of suppressing glare on a screen and image unsharpness without substantially impairing an antiglare function.

The transparent substrate of the invention is a transparent substrate with an anti-dazzle function,

the transparent substrate has a first surface and a second surface,

the resolution index value T, the reflection image diffusivity index value R, and the glare index value S of the transparent substrate, which are measured by the following methods, satisfy each of:

T≥0.25，

r is not less than 0.8, and

0.75≤S≤0.95。

here, the resolution index value T is obtained as follows:

irradiating a first light from the first surface side of the transparent substrate in a direction parallel to the thickness direction of the transparent substrate, measuring the brightness of a transmitted light (referred to as 0 DEG transmitted light) emitted from the second surface in a direction parallel to the thickness direction of the transparent substrate, and,

measuring the brightness of transmitted light (referred to as total transmitted light) transmitted through the transparent substrate and emitted from the second surface in an angular range of-30 DEG to +30 DEG with respect to a direction parallel to the thickness direction of the transparent substrate,

the calculation is performed according to the following formula (1),

the resolution index value T is (luminance of 0 ° transmitted light)/(luminance of total transmitted light) formula (1),

the reflection image diffusivity index value R is obtained as follows:

irradiating the transparent substrate with second light from the first surface side of the transparent substrate in a direction of +5.7 DEG with respect to a normal to the first surface,

measuring a first angle α from said first surface relative to said normal₁Brightness R of positively reflected first reflected light (-5.7 DEG + -0.1 DEG)₁And, furthermore,

at a first angle α corresponding to the first reflected light₁When the angle is 0 DEG, a second angle α is measured from the first surface₂(α₂Luminance R of second reflected light reflected at-0.5 ° ± 0.1 °)₂And α at a third angle from the first surface₃(α₃Brightness R of the third reflected light reflected at +0.5 ° ± 0.1 °)₃，

The calculation is performed according to the following equation (2),

the reflection image diffusivity index value R is (R)₂+R₃)/(2×R₁) The compound of the formula (2),

the glare index value S is obtained by:

the transparent substrate is disposed on the display surface side of the display device such that the second surface is on the display device side,

with the display device turned on, the Sparkle value of the transparent substrate was measured as the glare S using an analyzer SMS-1000_aAnd the same was carried out using a glass substrate (VRD140 glass) having a thickness of 1.6mmThe obtained Sparkle value was used as the glare S_sWhen the temperature of the water is higher than the set temperature,

calculated according to the following equation (3),

glare index value S is 1- (S)_a/S_s) Formula (3).

The present invention can provide a transparent substrate that can suppress glare on a screen and image unsharpness without substantially impairing an antiglare function.

Drawings

Fig. 1 is a schematic perspective view of a transparent substrate according to an embodiment of the present invention.

Fig. 2 is a diagram schematically showing an example of a measuring apparatus used for measuring the resolution index value T of the transparent substrate.

Fig. 3 is a diagram schematically showing an example of a measuring apparatus used for measuring the reflected image diffusivity index value R of the transparent base.

Detailed Description

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(transparent substrate according to one embodiment of the present invention)

Fig. 1 is a schematic perspective view of a transparent substrate (hereinafter, simply referred to as "transparent substrate") according to an embodiment of the present invention.

As shown in fig. 1, the transparent substrate 100 is generally rectangular and has a first surface 102 and a second surface 104 opposite to each other.

In the present invention, the form and shape of the transparent substrate 100 are not particularly limited. The transparent substrate 100 may be, for example, a plate, a film, a sheet, or the like. When the transparent substrate 100 is in the form of a film or a sheet, the transparent substrate 100 may be provided on an arbitrary support member. In addition, the transparent substrate 100 may have a circular, elliptical, or roll shape, for example, in addition to a rectangular shape.

The transparent substrate 100 may be made of any material as long as it is transparent. The transparent substrate 100 may be made of glass, resin, or the like, for example.

When the transparent substrate 100 is made of glass, the composition of the glass is not particularly limited. The glass may be, for example, soda lime glass or aluminosilicate glass.

When the transparent substrate is made of glass, the first surface and/or the second surface may be chemically strengthened.

Here, the chemical strengthening treatment is a generic term for a technique of immersing a glass substrate in a molten salt containing an alkali metal and replacing the alkali metal (ion) having a small ionic radius present on the outermost surface of the glass substrate with the alkali metal (ion) having a large ionic radius present in the molten salt. In the chemical strengthening treatment method, an alkali metal (ion) having a larger ion radius than the original atom is disposed on the surface of the glass substrate to be treated. Therefore, compressive stress can be applied to the surface of the glass substrate, thereby improving the strength (particularly, crack resistance) of the glass substrate.

The thickness of the transparent substrate 100 varies depending on the application, but is, for example, in the range of 0.1mm to 5 mm. Particularly, when used for a display device, the thickness is preferably 2mm or less.

The transparent substrate 100 is applied to, for example, a cover glass of a display device, a touch panel, and the like. The display device may be, for example, a television device, a computer, a tablet terminal, a smartphone, a cellular phone, an electronic blackboard, or the like.

Here, the transparent substrate 100 has the following features.

(i) The resolution index value T is 0.25 or more,

(ii) the reflection image diffusivity index value R is 0.8 or more,

(iii) the glare index value S is 0.75-0.95.

The resolution index value T is an index relating to the sharpness of an image displayed through the transparent substrate, and indicates that the higher the value is, the higher the sharpness of the image is. The reflection image diffusivity index value R is an index relating to the degree of reflection of the peripheral image on the transparent substrate, that is, the antiglare property, and indicates that the antiglare property of the transparent substrate is high as the reflection is suppressed as the value is larger. The glare index value S is an index related to glare, which is an uneven bright point generated by interference between lights (images) scattered by the transparent substrate when the lights (images) from the display device pass through the transparent substrate, and the smaller the value, the more significant the glare.

As described above, if an image from a display device is observed through a conventional transparent substrate having an antiglare function, the image may often be unclear or glare may occur on a display screen.

However, in the transparent substrate 100 satisfying the characteristics of (i) to (iii), the glare on the screen and the unsharpness of the observed image can be remarkably suppressed while obtaining the corresponding antiglare effect. In particular, in the transparent substrate 100, even if the resolution of an image displayed on a screen in a display device is improved in the future, it is expected that the occurrence of image blurring and glare is remarkably suppressed.

In general, if the value of the reflection image diffusivity index value R becomes large, the value of the glare index value S also tends to become large. If these index values become larger, the resolution index value T tends to become smaller. Therefore, it is very difficult to increase the total index value. When the resolution index value T is used for cover glass for a display device or the like, the value of the resolution index value T is usually preferably 0.8 or more, but when the transparent base 100 and a display panel of the display device are directly bonded with a resin or the like, the reflection image diffusivity index value R and the glare index value S are kept high even if the resolution index value T is suppressed to about 0.25 to 0.7, and as a result, the inventors of the present invention have found that the cover glass can obtain a clear image while enhancing the glare suppression effect and the antiglare effect.

(3 method of measuring index)

Here, a method of measuring the 3 indexes, that is, the resolution index value T, the reflection image diffusivity index value R, and the glare index value S will be described with reference to the drawings.

(resolution index value T)

First, a method of measuring the resolution index value T will be described with reference to fig. 2.

Fig. 2 schematically shows an example of a measurement device used for measuring the resolution index value T.

As shown in fig. 2, the measurement device 200 includes a light source 250 and a detector 270, and a sample to be measured, i.e., a transparent substrate a is disposed in the measurement device 200. The transparent substrate a has a first surface 212 and a second surface 214. The light source 250 emits the first light 262 toward the transparent substrate a. The detector 270 receives the transmitted light 264 emitted from the transparent substrate a and detects the brightness thereof.

The transparent substrate a is disposed so that the first surface 212 is on the light source 250 side and the second surface 214 is on the detector 270 side. Therefore, the light detected by the detector 270 is the transmitted light 264 transmitted through the transparent substrate a.

In the case where one surface of the transparent substrate a is subjected to the antiglare treatment, the antiglare-treated surface becomes the first surface 212 of the transparent substrate a. That is, in this case, the transparent substrate a is disposed in the measurement device 200 so that the antiglare-treated surface is on the light source 250 side.

In the measurement, the first light 262 is irradiated from the light source 250 toward the transparent substrate a. The first light 262 is irradiated in a direction substantially parallel to the normal to the first surface 212 (and the normal to the second surface 214) of the transparent substrate a. Hereinafter, the angle θ is defined as a direction of 0 °. Note that, since there is an error in actual measurement, more precisely, the angle θ includes a range of 0 ° ± 0.5 °.

Next, the brightness of the transmitted light 264 transmitted from the second surface 214 of the transparent substrate a at an angle θ of 0 ° (hereinafter also referred to as "0 ° transmitted light") was measured using the detector 270.

Then, the angle θ at which the detector 270 receives the transmitted light 264 is changed by 1 ° in the range of-30 ° to +30 °, and the same operation is performed. Here, the sign of minus (-) indicates that the angle θ is inclined counterclockwise with respect to the normal of the second surface 214, and the sign of plus (+) indicates that the angle θ is inclined clockwise with respect to the normal of the second surface 214.

Thus, the brightness of the transmitted light 264 (hereinafter also referred to as "total transmitted light") emitted from the second surface 214 through the transparent substrate a at an angle θ ranging from-30 ° to +30 ° is measured by the detector 270.

Next, the resolution index value T is calculated according to the following equation (1):

formula (1): resolution index value T ═ luminance of (0 ° transmitted light)/(luminance of total transmitted light)

It is determined that the resolution index value T obtained in such measurement is correlated with the result of determination of the resolution by visual observation by the observer, and shows a behavior close to human visual perception. For example, a transparent substrate showing a small (close to 0) value of the resolution index value T has a poor resolution, whereas a transparent substrate showing a large (close to 1) value of the resolution index value T has a good resolution. Therefore, the resolution index value T can be used as a quantitative index for determining the resolution of the transparent substrate.

Such measurement can be easily performed by using a commercially available goniometer (variable angle photometer).

(reflection image diffusivity index value R)

Next, a method for measuring the reflection image diffusivity index value R of the transparent base will be described with reference to fig. 3.

Fig. 3 schematically shows an example of a measuring device used for measuring the reflection image diffusivity index value R.

As shown in fig. 3, the measurement device 300 includes a light source 350 and a detector 370, and a sample to be measured, i.e., a transparent substrate a is disposed in the measurement device 300. The transparent substrate a has a first surface 212 and a second surface 214. The light source 350 emits a slit-shaped second light 362 having a width of 101mm toward the transparent substrate a. The detector 370 receives the reflected light reflected at a predetermined angle from the first surface 212, and detects the brightness thereof.

The transparent substrate a is disposed so that the first surface 212 is on the light source 350 and the detector 370 side. Therefore, the light detected by the detector 370 is reflected light reflected by the transparent substrate a. In addition, in the case where one surface of the transparent substrate a is subjected to the antiglare treatment, the antiglare treated surface is the first surface 212 of the transparent substrate a. That is, in this case, the transparent substrate a is disposed in the measurement device 300 so that the antiglare-treated surface faces the light source 350 and the detector 370.

In the measurement, the second light 362 is irradiated from the light source 350 of the measurement device 300 toward the transparent substrate a.

The second light 362 is irradiated to the transparent substrate a at an angle phi that is inclined counterclockwise by 5.7 deg. with respect to the direction of the normal line L of the transparent substrate a. It should be noted that the actual measurement is subject to errors, whereby more precisely the angle phi comprises the range of 5.7 deg. + -0.1 deg..

Next, the brightness R of the light regularly reflected from the first surface 212 of the transparent substrate a (hereinafter referred to as "first reflected light 364") is measured using the detector 370₁。

Note that, in reality, the angle of the first reflected light 364 with respect to the normal line L (first α)₁) Is α₁Is-phi and is therefore α₁-5.7 ° ± 0.1 °. The sign of minus (-) indicates that the angle is inclined counterclockwise with respect to the normal line L, and the sign of plus (+) indicates that the angle is inclined clockwise with respect to the normal line L.

However, here due to the first angle α of the first reflected light 364₁As a reference, therefore, defined as an angle α₁＝0°±0.1°。

Similarly, the second angle α measured from the first surface 212 of the transparent substrate A₂Brightness R of reflected light (hereinafter referred to as "second reflected light 366")₂And α at a third angle₃Brightness R of reflected light (hereinafter referred to as "third reflected light 368")₃Here, the second angle α₂At a first angle α₁On a basis of α₂-0.5 ° ± 0.1 °. additionally, a third angle α₃At a first angle α₁On a basis of α₃＝+0.5°±0.1°。

Using the respective luminances R obtained₁、R₂、R₃The reflection image diffusivity index value R of the transparent base a is calculated by the following formula (2):

formula (2): the reflection image diffusivity index value R is (R)₂+R₃)/(2×R₁)

It was confirmed that the reflected image diffusivity index value R indicates a behavior close to human visual perception in relation to the result of determination of reflected image diffusivity by visual observation by an observer. For example, it is shown that a transparent base having a large value (a value close to 1) of the reflection image diffusivity index value R has excellent reflection image diffusivity, whereas a transparent base having a small value of the reflection image diffusivity index value R tends to have poor reflection image diffusivity.

Such measurement can be performed by using, for example, SMS-1000, a device manufactured by DM & S.

In using the device, a C1614A lens with a focal length of 16mm was used with an aperture of 5.6. The distance from the first surface 212 of the transparent base A to the camera lens is about 300mm, and the imaging scale is set to be in the range of 0.0276 to 0.0278.

(glare index value S)

Next, a method for measuring the glare index value S of the transparent substrate will be described.

When the glare index value S is measured, a display device (iPad (registered trademark); resolution 64ppi) is prepared. A cover member for the purpose of preventing breakage or the like may be provided on the display surface side of the display device.

Next, a transparent substrate as a sample to be measured is disposed on the display surface side of the display device. When one surface of the transparent substrate a is subjected to the antiglare treatment, the transparent substrate a is disposed on the display surface side of the display device so that the antiglare treated surface is on the display device side.

Next, in a state where the display device is turned on to display an image, an analysis device (SMS-1000; DM) is used&Manufactured by S corporation), the degree of glare of the transparent substrate was subjected to image analysis. Thereby, the glare S expressed by spark value is obtained_a。

It is preferable that the image displayed on the display device is a simple green image composed of RGB (0, 255, 0), and is displayed on the entire display screen of the display device. This is to minimize the influence of appearance difference or the like due to difference in display color. The distance d between the fixed image-pickup element and the transparent substrate was 540 mm. When the distance d is represented by the distance index r, the distance corresponds to r being 10.8.

Next, the same measurement was performed on the reference sample. The reference sample was a Glass substrate (VRD140 Glass; manufactured by Asahi Glass Europe) having a thickness of 1.6 mm.

The obtained spark valueAs glare S_s。

According to the obtained S_aAnd S_sThe glare index value S of the transparent substrate a is calculated by the following formula (3).

Formula (3): glare index value S is 1- (S)_a/S_s)

It was confirmed that the glare index value S is related to the result of determination of glare by visual observation by an observer, and shows a behavior close to human visual perception. For example, a transparent substrate having a large glare index value S tends to have a significant glare, whereas a transparent substrate having a small glare index value S tends to have a suppressed glare.

In this measurement, a 23FM50SP lens having a focal length of 50mm is preferably used as the aperture 5.6.

(other features of the transparent substrate according to an embodiment of the present invention)

Next, other features of the transparent substrate 100 will be explained. Note that the features described below are arbitrarily assigned, and therefore it is necessary to note that they are not essential features in the present invention.

(hardness)

At least one surface of the transparent substrate 100 of an embodiment of the present invention may have a pencil hardness of more than 6H. At this time, the transparent substrate 100 is not easily scratched.

Here, the pencil hardness of the transparent substrate was measured by a method prescribed in JIS K5400 using a pencil hardness tester.

(haze)

The haze of the transparent substrate 100 according to an embodiment of the present invention may be 40 or less.

In general, if cover glass is provided on the surface of a display device having a black frame, the difference in color between the central portion and the frame portion is often noticeable, and the appearance of the black frame may be poor.

However, when the haze of the transparent substrate is 40 or less, even if the transparent substrate is provided on the surface of such a display device, the difference in color is not conspicuous, and the deterioration of the aesthetic appearance can be suppressed.

The haze of the transparent substrate was measured by a haze meter according to the method defined in JIS K-7136.

(finger and pen slipperiness)

The transparent substrate 100 according to an embodiment of the present invention may have a coefficient of kinetic friction of 0.4 or less. In addition or alternatively, the transparent substrate 100 according to an embodiment of the present invention may have a pen static friction coefficient in a range of 0.18 to 0.3.

When the transparent substrate is used as a touch panel that can be operated with fingers, good finger-sliding properties are required. Further, when the transparent substrate is used as a touch panel which can be operated with a pen, good pen-sliding properties are required. Otherwise, the user feels a sense of incongruity when he or she wants to perform various operations with a finger or a touch pen using the touch panel.

In this regard, when the transparent substrate 100 according to an embodiment of the present invention has the above-described coefficient of finger friction, when used as a touch panel, the user can feel good finger-slip properties that combine a moderate slippery feel and a grip feel (feel っかかり).

In addition, when the transparent substrate 100 according to an embodiment of the present invention has the pen static friction coefficient, the user feels a light feel of the ground when it is used as a touch panel, and thus, good writing comfort can be obtained.

Here, the "coefficient of dynamic friction" is an average value of the coefficient of dynamic friction obtained when the tactile contact simulating the shape of a finger is linearly moved on the surface of the measurement target at a load of 30g and a speed of 100mm/s for a movement distance in a range of 15mm to 35 mm.

The measurement was carried out at a temperature of 23 ℃ plus or minus 2 ℃ and a humidity of 50% + orminus 10%.

On the other hand, the "pen static friction coefficient" is a static friction coefficient obtained when a predetermined pen is linearly moved on a surface to be measured at a speed of 100mm/s under a load of 200g in a state of being inclined at 45 ° to a normal line of the surface to be measured (inclination angle of 45 °). The pen was a polyacetal core (ACK-20001; manufactured by Wacom Co., Ltd.). The moving direction is a direction perpendicular to a plane including the normal line and the pen. The measurement was carried out at a temperature of 23 ℃ plus or minus 2 ℃ and a humidity of 50% + orminus 10%.

(method for producing transparent substrate according to one embodiment of the present invention)

The transparent substrate 100 according to the embodiment of the present invention having the above-described features can be manufactured by any manufacturing method.

For example, the transparent substrate 100 can be manufactured by wet etching a glass substrate. In this method, for example, by using a mixed solution of hydrofluoric acid/sulfuric acid/ammonium fluoride as an etchant, the transparent substrate 100 having the above-described characteristics can be easily obtained.

Alternatively, the transparent substrate 100 may be manufactured by performing sand blasting on a glass substrate and then performing wet etching on the glass substrate.

In this method, for example, by reducing the particle size (for example, #2000 type or more) of the abrasive grains used for the blasting treatment, the transparent base 100 having the above-described characteristics can be easily obtained.