JP2016222515A - Glass sheet for light guide plate and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass sheet for light guide plate having enhanced brightness of the glass by reducing reflection coefficient of a glass surface.SOLUTION: There is provided a glass sheet for light guide plate having convexoconcave on at least one surface, average of reflection degree of the surface of light with wavelength of 400 to 700 nm at incident angle 0° in a spectrometry of 4.0% or less, total amount of iron in terms of FeOof 1 mass.ppm to 80 mass.ppm and Fein terms of FeOof 10 mass.ppm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a glass plate for a light guide plate and a method for producing the same.

  Conventionally, a thin display device such as a liquid crystal television includes a light guide plate, an optical film, a liquid crystal display, and the like, which are surface light emitters, and an acrylic resin has been used as the light guide plate (LGP; Light-Guiding Panel). However, in order to further reduce the thickness, weight, size, etc. of the display device, it has been studied to use a glass plate instead of an acrylic resin. Since the glass plate has higher rigidity than the acrylic resin, a reinforcing member is not necessary, and the weight of the entire apparatus can be reduced.

As a function improvement of the glass light guide plate, a method for improving luminance, a method for imparting an optical film function to glass, and the like have been studied. By increasing the luminance, it is possible to increase the screen size, reduce power consumption, improve image quality, and the like.
In order to improve the brightness, a method for suppressing the light absorption in the glass plate for the light guide plate and improving the transmittance by reducing the content of the colored oxide in the glass plate as much as possible is known. (Patent Document 1). In addition, it is known that the luminance can be improved by a method of increasing the light incident efficiency or a method of emitting light uniformly from the entire surface by the rear optical design.

  On the other hand, mainly for thin-film silicon solar cell applications, a glass substrate having irregularities formed on the glass surface by bringing a fluorinating agent into contact with the surface of the glass substrate, and at least 1. A glass substrate having an antireflection property of 0% or more is known (Patent Document 2).

  Moreover, a transparent member having a concave portion on the surface is obtained by performing a treatment using a fluorine atom-containing liquid in a solution subsequent to a treatment using a fluorine atom-containing gas, and the transparent member is particularly suitably applied to a light emitting module or the like. It is known that this can be done (Patent Document 3).

International Publication No. 2015/033866 International Publication No. 2012/141131 International Publication No. 2014/088011

As described above, various methods for improving the image quality of the glass for the light guide plate have been studied, and a method for treating the glass surface with a gas containing fluorine atoms for reducing the reflectance and improving the transparency of the glass is known. Yes.
However, in a highly transparent glass plate, especially a glass plate used for a light guide plate, it has been desired to further reduce the reflectance of the glass surface in order to increase the light output efficiency in order to increase the luminance.

  Then, this invention aims at providing the glass plate for light-guide plates which the brightness | luminance of glass improved by reducing the reflectance of the glass surface.

  As a result of intensive research, the inventors have contact with a glass plate with a predetermined amount or more of a fluorine-containing gas, thereby having irregularities on at least one surface and a low average reflectance for light having a wavelength of 400 to 700 nm. It discovered that the glass plate for light-guide plates was obtained, and came to complete this invention.

That is, the present invention relates to the following <1> to <4>.
<1> At least one surface has irregularities, and the average reflectance of the surface of light having a wavelength of 400 to 700 nm at an incident angle of 0 ° in the spectroscopic measurement is 4.0% or less, and converted to Fe ₂ O ₃ the total amount of iron 1 mass ppm or more and 80 mass ppm or less, and _Fe ^{Fe 2+} in terms of 2 _{O 3} is at most 10 mass ppm, the light guide plate glass plate.
<2> The average value R of the reflectance of the surface of light having a wavelength of 600 to 650 nm, the average value G of the reflectance of the surface of light having a wavelength of 500 to 600 nm, and a wavelength of 430 at an incident angle of 0 ° in spectroscopic measurement. The glass for a light guide plate according to <1>, wherein an average value B of reflectance of the surface of light of ˜460 nm satisfies a relationship of an average value B ≦ average value R and an average value B ≦ average value G Board.
<3> The glass for a light guide plate according to <1> or <2>, wherein an average reflectance of the surface of light having a wavelength of 400 to 700 nm at an incident angle of 42 ° in the spectroscopic measurement is 0.20% or less. Board.
<4> A method for producing the glass plate for a light guide plate according to any one of <1> to <3>,
Including a step of bringing a fluorine-containing gas into contact with the glass plate,
The manufacturing method of the glass plate for light-guide plates whose total contact amount to the said glass plate of the said fluorine-containing gas is 3.0 * 10 < ^-4 > mol / cm < ² > or more in conversion of a fluorine element.

  According to the present invention, a glass plate for a light guide plate having an excellent antireflection effect and a low average reflectance can be obtained. For this reason, when used as a display for a television or the like, the brightness can be increased by improving the dispatching efficiency, an improvement in image quality is expected, a load on a device such as a television is small, and an energy saving effect is also expected.

  Furthermore, depending on the uneven shape of the glass surface, the reflection of light in the B region (wavelength 430 to 460 nm) in the RGB color model can be made particularly low, so color control for preventing yellowing is unnecessary or minimized. be able to.

It is a conceptual diagram of the apparatus used in the Example. 2 is a scanning electron microscope (SEM) photograph of the glass surface of Example 10. FIG. 2 is a SEM photograph of a glass cross section of Example 10.

  Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the gist of the present invention.

<Glass plate>
The glass plate for a light guide plate according to the present invention (hereinafter sometimes simply referred to as “the glass plate according to the present invention”) has at least one surface, and has a wavelength of 400 to 400 at an incident angle of 0 ° in spectroscopic measurement. The average value of the reflectance of the surface of 700 nm light is 4.0% or less, the total amount of iron converted to Fe ₂ O ₃ is 1 mass ppm to 80 mass ppm, and Fe ₂ O ₃ converted to Fe ₂ O ₃ ²⁺ is 10 mass ppm or less.

A light guide plate (LGP) is a plate used in an edge light system (a system in which light entered from a side surface of a plate is diffused to emit uniform light on the surface). Since light enters from the side surface of the plate, it is not necessary to adopt a backlight system in which a light source such as a fluorescent lamp or LED is inserted on the back side, and a thin and uniform plate can be obtained.
As a specific use of the light guide plate, it can be used for a small liquid crystal, a notebook personal computer, an LCD monitor, a liquid crystal television and the like.

  The glass plate according to the present invention is preferably highly transmissive glass. The main factor of light absorption of the glass plate is iron ions contained as impurities. Iron is unavoidably contained as a raw material for industrially produced glass, and it is inevitable that iron is mixed into the glass.

The content of total iron oxide _(t-Fe 2 _{O 3)} which in terms of Fe ₂ O ₃ is 80 mass ppm or less in order to achieve very high transmittance over the entire visible range. The content of t-Fe ₂ O ₃ is more preferably 60 ppm by mass or less, further preferably 50 ppm by mass or less, particularly preferably 40 ppm by mass or less, and most preferably 35 ppm by mass or less. .

On the other hand, the t-Fe ₂ O ₃ content of the glass plate of the present invention is 1 ppm by mass or more. If it is less than 1 mass ppm, it becomes difficult to improve the meltability of the glass during the production of the multi-component oxide glass, and it is difficult to mass-produce at a low cost. Moreover, it is difficult to obtain raw materials. Preferably it is 5 mass ppm or more, More preferably, it is 8 mass ppm or more, More preferably, it is 10 mass ppm or more. The amount of t-Fe ₂ O ₃ in the glass plate can be adjusted by the amount of iron component added during glass production.

The total amount of iron oxide contained in the glass plate is expressed as the amount of Fe ₂ O ₃ , but not all iron present in the glass is present as Fe ³⁺ (trivalent iron). Usually, Fe ³⁺ and Fe ²⁺ (divalent iron) are simultaneously present in the glass (hereinafter, these are collectively referred to as “iron component”). Although iron component has an absorption in the visible light region, the absorption coefficient of the ^{Fe 2+ (11cm -1 Mol} -1), since an order of magnitude greater than the absorption coefficient of the ^{Fe 3+ (0.96cm -1 Mol -1)} , visible The internal transmittance of the light region is further reduced. Therefore, it is preferable that the Fe ²⁺ content is small in order to increase the internal transmittance in the visible light region.

In the glass plate of the present invention, the content of divalent iron (Fe ²⁺ ) converted to Fe ₂ O ₃ is suppressed to 10 ppm by mass or less. Preferably it is 8.0 mass ppm or less, More preferably, it is 6.0 mass ppm or less, Especially preferably, it is 4.0 mass ppm or less, Most preferably, it is 3.5 mass ppm or less.

  The composition of the glass plate according to the present invention is not particularly limited as long as it has the aforementioned characteristics. For example, the following three types (glass having glass composition A, glass composition B, and glass composition C) are given as typical examples.

Glass plate is a glass composition A is a mass percentage based on oxides, essentially, a SiO ₂ 60-80%, the _Al 2 _{O 3 0~7%,} the MgO 0%, the CaO 0 20% 0 to 15% of SrO 0 to 15% of BaO, Na ₂ O 3 to 20%, and _{K 2} O may also contain 0-10%.

Glass plate is a glass composition B is a mass percentage based on oxides, essentially, a _{SiO 2 45~80%, Al 2 O} 3 7 percent 30% or _less, B 2 _{O 3} 0-15 %, the MgO 0 to 15%, Less than six% of CaO, the SrO 0 to 5%, 0 to 5% of BaO, 7 to 20% of Na ₂ O, 0% to _{K 2} O, and ZrO ₂ may be included in an amount of 0 to 10%.

The glass plate having the glass composition C substantially contains 45 to 70% of SiO ₂ , 10 to 30% of Al ₂ O _3, and 0 to 15% of B ₂ O ₃ in terms of oxide-based mass percentage. In addition, at least one component selected from the group consisting of MgO, CaO, SrO and BaO is included in total 5 to 30%, and at least one selected from the group consisting of Li ₂ O, Na ₂ O and K ₂ O These components may be included in total from 0% to less than 3%.

The composition range of each component of the glass composition of the glass plate of the present invention having the above-described components will be described below. In this specification, the components of glass are expressed in terms of oxides such as SiO ₂ and Al ₂ O ₃ , and the content (glass composition) of each component with respect to the entire glass is expressed in terms of mass percentage based on oxide or mass ppm ( The mass percentage is simply expressed as%, or the mass ppm may be simply expressed as ppm).

SiO ₂ is a main component of glass.
In order to maintain the weather resistance and devitrification properties of the glass, the content of SiO ₂ is preferably 60% or more, more preferably 63% or more in the glass composition A in terms of the oxide-based mass percentage. In composition B, it is preferably 45% or more, more preferably 50% or more, and in glass composition C, it is preferably 45% or more, more preferably 50% or more.
On the other hand, the upper limit of the content of SiO ₂ is to make dissolution easy and to improve the foam quality, and to keep the content of divalent iron (Fe ²⁺ ) in the glass low and to improve the optical characteristics. Therefore, in the glass composition A, it is preferably 80% or less, more preferably 75% or less, and in the glass composition B, preferably 80% or less, more preferably 70% or less. In C, it is preferably 70% or less, more preferably 65% or less.

Al ₂ O ₃ is an essential component for improving the weather resistance of glass in the glass compositions B and C. In order to maintain practically necessary weather resistance in the glass of the present invention, the content of Al ₂ O ₃ is preferably 1% or more, more preferably 2% or more in the glass composition A, and the glass composition In B, it is preferably more than 7%, more preferably 10% or more, and in the glass composition C, it is preferably 10% or more, more preferably 13% or more.
However, in order to keep the content of divalent iron (Fe ²⁺ ) low, make the optical properties good, and make the foam quality good, the content of Al ₂ O ₃ is preferably in the glass composition A. Is 7% or less, more preferably 5% or less. In the glass composition B, preferably 30% or less, more preferably 23% or less. In the glass composition C, preferably 30% or less, more preferably 20% or less.

B ₂ O ₃ is a component that promotes melting of the glass raw material and improves mechanical properties and weather resistance. However, in a soda lime silicate glass such as the glass composition A, the striae due to volatilization (ream) Is preferably 5% or less, more preferably 2% or less, particularly preferably 1% or less, and substantially does not contain. Is most preferred. Hereinafter, the term “substantially not containing” in the present specification means not containing any inevitable impurities. Further, in the glass compositions B and C, the content of B ₂ O ₃ is preferably 15% or less, more preferably 12% or less, but it is not an essential component.

Alkali metal oxides such as Li ₂ O, Na ₂ O, and K ₂ O are useful components for accelerating melting of glass raw materials and adjusting thermal expansion, viscosity, and the like.
Therefore, in the glass composition A, the content of Na ₂ O is preferably 3% or more, more preferably 8% or more. In the glass composition B, the content of Na ₂ O is preferably 7% or more, more preferably 10% or more. However, the content of Na ₂ O is preferably 20% or less in the glass compositions A and B in order to maintain the clarity during melting and maintain the foam quality of the produced glass, and 15% The following is more preferable. In the glass composition C, it is preferably 3% or less, more preferably 1% or less, but it is not an essential component.

Further, in the glass compositions A and B, the content of K ₂ O is preferably 10% or less, more preferably 7% or less, and may not be included. In the glass composition C, it is preferably 2% or less, more preferably 1% or less, but it is not an essential component.

Further, Li ₂ O is an optional component, but in order to facilitate vitrification, to keep the iron content contained as impurities derived from the raw material low, and to keep the batch cost low, in the glass compositions A and B, Li ₂ O can be contained in an amount of 5% or less, more preferably 2% or less. In the glass composition C, less than 3% is preferable.

In addition, the total content of these alkali metal oxides (Li ₂ O + Na ₂ O + K ₂ O) maintains the clarification at the time of melting, and in order to maintain the foam quality of the produced glass, in the glass compositions A and B , Preferably 5% to 20%, more preferably 8% to 15%. In the glass composition C, preferably 0% or more and less than 3%, more preferably 0% to 2%, still more preferably 0%. ~ 1%.

  Alkaline earth metal oxides such as MgO, CaO, SrO, and BaO are useful components for accelerating melting of glass raw materials and adjusting thermal expansion, viscosity, and the like.

  MgO has the effect of lowering the viscosity during glass melting and promoting the melting. Moreover, since there exists an effect | action which reduces specific gravity and makes a glass plate hard to be wrinkled, it can be contained in glass composition A, B, and C. In order to make the glass have a low coefficient of thermal expansion and good devitrification properties, the content of MgO in the glass composition A is preferably 10% or less, more preferably 8% or less, and even more preferably 5%. In the glass composition B, preferably 15% or less, more preferably 12% or less, further preferably 10% or less, and in the glass composition C, preferably 10% or less, more preferably 5% or less. It is.

  CaO is a component that promotes melting of the glass raw material and adjusts viscosity, thermal expansion, and the like, and therefore can be contained in the glass compositions A, B, and C. In order to obtain the above action, in the glass composition A, the content of CaO is more preferably 3% or more, and further preferably 5% or more. In order to improve devitrification, the glass composition A is preferably 20% or less, more preferably 10% or less, and the glass composition B is preferably 6% or less, more preferably 4% or less.

  SrO has the effect of increasing the thermal expansion coefficient and lowering the high temperature viscosity of the glass. In order to obtain such an effect, SrO can be contained in the glass compositions A, B and C. However, in order to keep the thermal expansion coefficient of the glass low, in the glass compositions A and C, the SrO content is preferably 15% or less, more preferably 10% or less, and in the glass composition B, 5%. % Or less, and more preferably 3% or less.

  BaO, like SrO, has the effect of increasing the thermal expansion coefficient and lowering the high temperature viscosity of the glass. In order to obtain the above effect, BaO can be contained. However, in order to keep the thermal expansion coefficient of the glass low, the content of BaO in the glass compositions A and C is preferably 15% or less, more preferably 10% or less, and 5% in the glass composition B. The content is preferably set to 3% or less, more preferably 3% or less.

  Further, the total content of these alkaline earth metal oxides (MgO + CaO + SrO + BaO) is preferably 10 in the glass composition A in order to keep the coefficient of thermal expansion low, good devitrification properties, and maintain strength. % Or more, more preferably 13% or more. In the glass composition B, preferably 1% or more, more preferably 10% or more. In the glass composition C, preferably 5% or more, more preferably 10% or more. It is. However, if the amount is increased, the amount of other components is relatively reduced, which causes a problem in devitrification characteristics and strength. Therefore, in the glass composition A, 30% or less is preferable, and more preferably 27% or less. In composition B, it is preferably 15% or less, more preferably 10% or less, and in glass composition C, it is preferably 30% or less, more preferably 20% or less.

In the composition of the glass plate of the present invention, in order to improve the heat resistance and surface hardness of the glass, ZrO ₂ is optionally contained in the glass compositions A, B and C in an amount of 10% or less, preferably 5% or less. May be. However, if it exceeds 10%, the glass tends to be devitrified, which is not preferable.

The glass of the glass plate of the present invention may contain SO ₃ as a fining agent. In this case, the SO ₃ content is preferably more than 0% and 0.5% or less in terms of mass percentage. 0.4% or less is more preferable, 0.3% or less is more preferable, and 0.25% or less is further preferable.

The glass of the glass plate of the present invention may contain one or more of _Sb 2 _O 3, SnO ₂ and _As 2 _{O 3} as an oxidizing agent and a clarifying agent. In this case, the content of Sb ₂ O ₃ , SnO ₂ or As ₂ O ₃ is preferably 0 to 0.5% in terms of mass percentage. 0.2% or less is more preferable, 0.1% or less is more preferable, and it is further more preferable not to contain substantially.

However, since Sb ₂ O ₃ , SnO ₂ and As ₂ O ₃ act as an oxidizing agent for glass, they may be added within the above range depending on the purpose of adjusting the amount of Fe ^{2+ in} the glass. However, As ₂ O ₃ is not positively contained from the environmental viewpoint.

The glass of the glass plate of the present invention may contain TiO ₂ . When TiO ₂ is contained, TiO ₂ also functions as a component that absorbs visible light. Therefore, the content of TiO ₂ is preferably 1000 ppm or less with respect to the total amount of the glass composition described above. From the viewpoint of not reducing the internal transmittance of the glass plate at a wavelength of 400 to 700 nm, the content of TiO ₂ is more preferably 500 ppm or less, and particularly preferably 100 ppm or less.

Glass of the glass plate of the present invention may contain CeO _2. CeO ₂ has the effect of reducing the redox of iron, and can reduce the absorption of glass with respect to light having a wavelength of 400 to 700 nm. However, if containing CeO ₂ in a large amount, CeO _2, compared the total amount of the glass composition described above to function as a component which absorbs visible light not only causes solarization, and 1000ppm or less Is preferred. The CeO ₂ content is more preferably 500 ppm or less, further preferably 400 ppm or less, particularly preferably 300 ppm or less, and most preferably 250 ppm or less.
When added, it is preferable that 0.1 ppm or more is always added in order to easily suppress variations in product characteristics during production, particularly color variations. Addition of 1.0 ppm or more is preferable for color control, and addition of 5.0 ppm or more is more preferable. When the effect of lowering the redox of iron is expected, it is preferable to add at least the same amount as the amount of iron (mass ppm) converted to Fe ₂ O ₃ contained in the glass, and 1.5 times the mass of iron More preferably, the addition is more preferably 3 times or more, still more preferably 5 times or more.

  Moreover, the glass of the glass plate of this invention may contain NiO. When NiO is contained, since NiO functions also as a coloring component, the content of NiO is preferably 10 ppm or less with respect to the total amount of the glass composition described above. In particular, NiO is preferably 1.0 ppm or less, more preferably 0.8 ppm or less, and more preferably 0.6 ppm or less from the viewpoint of not reducing the internal transmittance of the glass plate due to light having a wavelength of 400 to 700 nm. More preferably, it is particularly preferably 0.5 ppm or less.

The glass of the glass plate of the present invention may contain Cr ₂ O ₃ . When Cr ₂ O ₃ is contained, Cr ₂ O ₃ also functions as a coloring component. Therefore, the content of Cr ₂ O ₃ is preferably 10 ppm or less with respect to the total amount of the glass composition described above. In particular, Cr ₂ O ₃ is preferably 2.0 ppm or less, more preferably 1.6 ppm or less, from the viewpoint of not reducing the internal transmittance of the glass plate due to light having a wavelength of 400 to 700 nm. More preferably, the content is not more than .2 ppm, particularly preferably not more than 1.0 ppm, more preferably not more than 0.8 ppm, and most preferably not more than 0.6 ppm.

The glass of the glass plate of the present invention may contain MnO ₂ . When MnO ₂ is contained, since MnO ₂ functions also as a component that absorbs visible light, the content of MnO ₂ is preferably 50 ppm or less with respect to the total amount of the glass composition described above. In particular, MnO ₂ is preferably 30 ppm or less, more preferably 20 ppm or less, and further preferably 15 ppm or less from the viewpoint of not reducing the internal transmittance of the glass plate due to light having a wavelength of 400 to 700 nm. It is preferably 10 ppm or less.

The glass of the glass plate of the present invention may contain at least one component selected from the group consisting of Se, CoO, V ₂ O ₅ and CuO. When these components are contained, they also function as components that absorb visible light. Therefore, the content of each component is preferably 5.0 ppm or less, more preferably 2.0 ppm or less. More preferably, it is 0 ppm or less. In particular, it is most preferable that these components are not substantially contained so as not to lower the internal transmittance of the glass plate due to light having a wavelength of 400 to 700 nm.

  The thickness of the glass plate may be 0.5 to 4 mm as a whole, and 1.5 to 3.5 mm is preferable from the viewpoint of maintaining rigidity necessary for the light guide plate.

  The irregularities on the glass plate surface according to the present invention can be formed by bringing a fluorine-containing gas into contact with the glass plate surface at a high temperature. That is, the unevenness on the surface of the glass plate is the surface of the glass plate used as a raw material is partially etched to make it uneven, and is combined with other members such as forming a film having unevenness on the glass plate surface. Not a thing. In addition, an unevenness | corrugation may be formed only in one surface of a glass plate, and an unevenness | corrugation may be formed in both surfaces.

  The formation of irregularities on the surface means that a large number of holes (open holes) are formed on the surface of the glass plate, and is defined in JIS B 0601 (1994) in the surface shape observed by AFM. The surface roughness (Ra) is preferably 0.3 nm or more, and more preferably 0.5 nm or more.

  The thickness of the concavo-convex layer on the glass surface is preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less from the viewpoint of maintaining the concavo-convex structure. In addition, it is preferable that the thickness of the concavo-convex layer is thin from the viewpoint that the amount of gas used to form the concavo-convex layer may be small. In addition, the thickness of an uneven | corrugated layer can be measured from the image at the time of carrying out SEM observation of the cross section of a glass plate.

The uneven layer becomes thicker as the total contact amount of the fluorine-containing gas increases, and becomes thinner as the total contact amount of the fluorine-containing gas decreases.
Since the specific conditions vary depending on the glass material, the type of fluorine-containing gas used, and the contact temperature, the conditions are appropriately changed to adjust the thickness of the concavo-convex layer.

The glass plate which concerns on this invention can reduce a reflectance by having an unevenness | corrugation in the surface. That is, by providing an uneven layer between the glass plate bulk layer (refractive index of about 1.45 to 1.96) and the air layer (refractive index of about 1.00), the refractive index of the bulk layer is gradually increased. Since the refractive index of the air layer can be changed, the amount of light reflected at the interface between the glass layer and the air layer can be reduced, and low reflection can be realized.
Due to the decrease in reflectance due to the unevenness of the surface, high luminance can be realized when a glass plate is used as the light guide plate.

In addition, the glass plate according to the present invention has excellent scratch resistance because of the smooth surface irregularity. The uneven shape on the surface can be made smooth by increasing the contact temperature of the fluorine-containing gas. It can be said that it is smooth if the uneven shape on the surface has no corners and is rounded.
In order to smooth the uneven shape, it is preferable that the contact temperature of the fluorine-containing gas is high, and that the total contact amount of the fluorine-containing gas is large. However, if the contact temperature is too high or the total contact amount is too large, the unevenness may become too smooth, resulting in a flat surface.
Since the specific fluorine-containing gas contact conditions differ depending on the glass material and the fluorine-containing gas used, the smoothness of the unevenness is adjusted by changing the conditions as appropriate.

The reflectance can be obtained by spectroscopic measurement.
The reflectance of light having a wavelength of 400 to 700 nm at an incident angle of 0 ° on the surface having irregularities of the glass plate according to the present invention is 4.0% or less as an average value of the reflectance. When measuring the reflectance of only one side of the glass plate, it can be measured by painting the surface of the glass not to be measured black.
In the spectroscopic measurement, it is more preferable that the average value of the reflectance of the surface having irregularities of light having a wavelength of 400 to 700 nm at an incident angle of 0 ° is 3.4% or less.

  In the glass plate, the reflectance of light in the B region (wavelength 430 to 460 nm) of the RGB color model is higher than the reflectance of light in the R region (wavelength 600 to 650 nm) and the reflectance of light in the G region (500 to 600 nm). If it is high, the blue coloration becomes relatively weak. In that case, since the image becomes yellowish as a whole, in the light guide plate application, it is necessary to adjust the color by intentionally reducing the light in the B region in order to prevent yellowing.

Since reducing the light for color adjustment reduces the overall brightness, it is desirable to minimize color control.
The glass plate which concerns on this invention can reduce the reflectance of each light of B area | region, R area | region, and G area | region by contacting a fluorine-containing gas and forming an unevenness | corrugation in the surface. In addition, the reflectance of light in the R region (wavelength 600 to 650 nm) can be particularly reduced by changing the conditions for contacting the fluorine-containing gas.

In order to suppress the color adjustment unnecessary or to the minimum, in the spectroscopic measurement, the average value R of the reflectance of one side of light having a wavelength of 600 to 650 nm and the reflectance of one side of light having a wavelength of 500 to 600 nm at an incident angle of 0 °. And the average value B of the reflectance of one side of light having a wavelength of 430 to 460 nm preferably satisfy the relationship of average value B ≦ average value R and average value B ≦ average value G.
The contact conditions of the fluorine-containing gas to obtain a glass plate that satisfies the above relationship vary depending on the glass material, the type of fluorine-containing gas used, the contact temperature, etc., so changing the conditions for each sample makes the color adjustment unnecessary or minimal The average value of the reflectance in each region is adjusted so that the process can be completed.

In order to satisfy the relationship of average value B ≦ average value R and average value B ≦ average value G, for example, when the glass material is soda-lime glass and the fluorine-containing gas is hydrogen fluoride (HF), contact At a temperature of 670 ° C., the total contact amount of hydrogen fluoride is preferably 1.3 × 10 ⁻³ (mol / cm ² ) or less. Further, at a contact temperature of 720 ° C., the total contact amount of the fluorine-containing gas is preferably 2.0 × 10 ⁻³ (mol / cm ² ) or less. Moreover, it is preferable that the total contact amount of hydrogen fluoride is 1.2 × 10 ⁻³ (mol / cm ² ) or less at a contact temperature of 770 ° C. However, in order to obtain a sufficient antireflection effect, the lower limit is preferably set to 3.0 × 10 ⁻⁴ mol / cm ² or more.
Thus, even if the glass material and the fluorine-containing gas are the same, the preferred total contact amount of the fluorine-containing gas varies depending on the contact temperature. For this reason, it is necessary to appropriately determine the optimum contact conditions for the fluorine-containing gas.

In addition, the total contact amount in terms of fluorine element of the fluorine-containing gas in this specification can be obtained according to the following formula.
[Total contact amount of fluorine-containing gas (mol / cm ² )] = [fluorine concentration (volume%)] / 100 × [gas flow rate (mol / second / cm ² )] × [treatment time (second)]
In the formula, the processing time is the time during which the fluorine-containing gas is in contact with the glass plate surface. The fluorine concentration is a value determined based on the fluorine-containing gas concentration. That is, when HF is used as the fluorine-containing gas, the fluorine-containing gas concentration and the fluorine element concentration are the same, but when SiF ₄ is used, the fluorine concentration is four times the fluorine-containing gas concentration.

When a glass plate is used for the light guide plate, an edge light system is adopted. At that time, the rear optical design is necessary to improve the light output efficiency, but the light irregularly reflected by the light guide pattern is totally reflected on the light exit surface (reflective surface) and incident on the light output surface at an angle less than the critical angle. Therefore, it is necessary to suppress recursion due to reflection on the exit surface. The critical angle varies depending on the refractive index of glass and the refractive index of air, but is approximately 42 °.
Therefore, the glass plate according to the present invention has an emission surface whose average reflectance of a surface on which irregularities of light having a wavelength of 400 to 700 nm at an incident angle of 42 ° are formed in spectroscopic measurement is 0.20% or less. It is preferable from the point of emitting light uniformly from the whole.

<Method for producing glass plate>
The glass plate which concerns on this invention can obtain the glass plate which has an uneven | corrugated shape on the surface by including the process which makes fluorine-containing gas contact a glass plate. The glass plate is _Fe 2 total iron in terms of _{O 3} is more than 1 mass ppm 80 ppm by weight or less, and ^{Fe 2+} in terms of _Fe 2 _{O 3} or lower is used 10 mass ppm.
In the step of contacting, by making the total contact amount of the fluorine-containing gas to the glass plate to be 3.0 × 10 ⁻⁴ mol / cm ² or more, a sufficient antireflection effect is obtained, and a glass plate having low reflectance is obtained. Can be obtained.
Since an uneven shape is formed on the surface contacted with the fluorine-containing gas, when the fluorine-containing gas is brought into contact with one surface of the glass plate, only the average reflectance of one surface is lowered, and when the fluorine-containing gas is brought into contact with both surfaces The average reflectance on both sides is lowered.

  By bringing the fluorine-containing gas into contact with each other, the surface of the glass plate is etched, and an uneven shape can be formed. Fluorine-containing gas contains fluorine atoms as part of its chemical structure, and breaks the bonds between oxygen atoms and metal atoms that constitute the oxide contained in the glass skeleton, and bonds between fluorine atoms and metal atoms. A substance capable of forming can be used. In addition, as a result of decomposition by heat, etc., fluorine atoms are included as part of the chemical structure, and bonds between fluorine atoms and metal atoms are formed by cutting the bonds between oxygen atoms and metal atoms in the glass skeleton. Possible substances can also be used.

As such a fluorine-containing gas, a fluorine compound capable of forming a bond between a fluorine atom and a metal atom by cutting a bond between an oxygen atom and a metal atom in the glass skeleton can be given.
Specifically, fluorine alone (F ₂ ), hydrogen fluoride (HF), trifluoroacetic acid, silicon tetrafluoride (SiF ₄ ), phosphorus pentafluoride (PF ₅ ), phosphorus trifluoride (PF ₃ ), Examples thereof include boron trifluoride (BF ₃ ), nitrogen trifluoride (NF ₃ ), and chlorine trifluoride (ClF ₃ ), but are not limited to these gases. Moreover, you may dilute with gas, such as nitrogen, as needed.
These fluorine-containing gases may be used alone or in a mixture of two or more. Among the above fluorinating agents, hydrogen fluoride is preferable because it has high reactivity with the surface of the glass plate, and because it can be processed in a short time on a glass plate being conveyed at a high speed, and productivity is very high. .

The fluorine-containing gas used in the present invention may contain a gas not containing fluorine, and is preferably a gas that does not react with the fluorine-containing gas at room temperature. Examples thereof include, but are not limited to, N ₂ , air, H ₂ , O ₂ , Ne, Xe, CO ₂ , Ar, He, and Kr. Moreover, 2 or more types can also be mixed and used among these gases. It is preferable to use an inert gas such as N ₂ or argon as the carrier of the fluorine compound and those diluted.

Further, SO ₂ may be mixed in the fluorine-containing gas used in the present invention. SO ₂ is used when continuously producing a glass plate by a float method or the like, and has a function of preventing wrinkles on the surface of the glass plate due to the conveyance roller coming into contact with the glass plate in the slow cooling region. Moreover, the gas decomposed | disassembled at high temperature may be included.

  Furthermore, water vapor may be mixed with the fluorine-containing gas. For example, when HF is used as the fluorine-containing gas, the molar ratio of HF to water vapor ([water] / [HF]) is preferably 10 or less. When HF and water vapor coexist, it is considered that hydrogen bonds are formed between HF molecules and water molecules, and HF acting on the glass plate is reduced. When [water] / [HF] exceeds 10, the amount of HF acting on the glass becomes very small, and as a result, the average value of the reflectance from 400 nm to 700 nm as compared with the untreated glass plate increases. [Water] / [HF] is more preferably 5 or less from the viewpoint that HF acting on the glass plate does not decrease.

  There are various methods of bringing the fluorine-containing gas into contact with the glass plate, such as a method of allowing the glass plate to stand in the gas atmosphere, but a method of spraying the fluorine-containing gas onto the glass plate is more preferable. In particular, a method in which a gas containing a fluorine-containing gas is sprayed onto a glass plate from a gas spraying device called an injector used in a CVD film forming method is preferable because the in-plane distribution of the processing surface can be easily made uniform.

  By treating the glass plate surface with a fluorine-containing gas, fluorine atoms are arranged in the bulk glass, and a low refractive index layer having a refractive index lower than that of untreated glass is formed on the bulk glass surface. The Therefore, it is possible to produce a glass plate having a low average reflectance of light having a wavelength of 400 to 700 nm and a high antireflection effect.

As the total contact amount of the fluorine-containing gas with the glass plate increases, the surface etching proceeds. By setting the total contact amount of the fluorine-containing gas to the glass plate to be 3.0 × 10 ⁻⁴ mol / cm ² or more, the surface of the surface on which unevenness of light having a wavelength of 400 to 700 nm at an incident angle of 0 ° is formed in spectroscopic measurement. A glass plate having an average reflectance of 4.0% or less can be obtained, and a sufficient antireflection effect can be obtained.
In addition, if the etching conditions with the fluorine-containing gas are too strict, the uneven shape of the surface may collapse and become flat, so the total amount of fluorine-containing gas should be considered while considering the type of glass material and fluorine-containing gas and the contact temperature. It is necessary to adjust the contact amount.

  The preferred contact temperature of the fluorine-containing gas to the glass plate varies depending on the type of glass material and fluorine-containing gas and the total contact amount. In general, the temperature is preferably 400 ° C. or higher. When the contact temperature is increased, the glass plate is excellent in scratch resistance because it is exposed to a high temperature and the shape of each of the concave and convex portions on the surface of the glass plate becomes smooth. For this reason, when the glass transition temperature is Tg, the treatment temperature is preferably Tg ° C. or higher, and more preferably Tg + 100 ° C. or higher. On the other hand, when the contact temperature is too high, the surface of the glass plate is melted, resulting in a flat surface with small unevenness. Therefore, the upper limit of the contact temperature is preferably Tg + 240 ° C. or less, and more preferably Tg + 220 ° C. or less.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these.
<Glass material>
A glass plate (thickness: 2.5 mm, Tg: 567 ° C.) having the following composition (mass% or mass ppm) was used.
_{SiO 2: 69.7%, Al 2} O 3: 3%, CaO: 8%, SrO: 4%, BaO: 4%, Na 2 O: 11%, CeO 2: 250ppm, t-Fe 2 O 3: 30 ppm, Fe ²⁺ (Fe ₂ O ₃ conversion): 0.5 ppm

<SEM observation>
For SEM observation, SU8000 manufactured by Hitachi High-Technologies Corporation was used, and the surface or cross section of the glass plate as a sample was observed after Pt sputtering. The acceleration voltage was 1.5 kV.
From the SEM image, the presence or absence of irregularities on the glass surface and the thickness of the irregular layer when there were irregularities were measured.

<Spectroscopic measurement 1>
The spectroscopic measurement was performed using JASCO V-670. The surface on which the fluorine-containing gas is not contacted is painted black, and light is incident from the treated surface that is in contact with the fluorine-containing gas with an incident angle of 0 ° (perpendicular to the glass plate surface), and the reflectance is determined. It was measured. The wavelength was 400 to 700 nm, and the average value was defined as the average reflectance (%) of one surface on which the irregularities were formed.
The same applies to light having a wavelength of 600 to 650 nm (R region), light having a wavelength of 500 to 600 nm (G region), and light having a wavelength of 430 to 460 nm (B region). Average reflectance (%) was determined.

<Spectroscopic measurement 2>
Except that the incident angle was set to 42 [deg.], The average reflectance (%) of one surface on which irregularities were formed at a wavelength of 400 to 700 nm at an incident angle of 42 [deg.] Was measured in the same manner as in <spectral measurement 1>.

<Example 1>
A gas containing hydrogen fluoride (HF) was brought into contact with the surface on one side of the glass plate using the double-flow injector 10 used in the atmospheric pressure CVD method as shown in the schematic diagram of FIG. 1 (HF treatment). . That is, from the central slit 1 shown in FIG. 1, a gas mixed with HF 2.00 SLM (liters of gas in a standard state and liter per minute) and nitrogen 48.0 SLM is heated to 200 ° C. at a flow rate of 100 cm / sec. 2 to N ₂ 50.0 SLM was similarly heated to 200 ° C. and sprayed toward the surface on one side of the glass plate to obtain a glass plate having an uneven structure on the surface. The gas flows on the glass plate 20 through the flow path 4, and 350 SML is exhausted in the exhaust slit 5. A hot-wire anemometer (manufactured by Kanomax Co., Ltd., Kurimo Master 6543) was used for measurement of gas temperature and flow velocity. The glass plate was heated to 670 ° C. and conveyed in the direction of arrow 21 at a speed of 2.9 m / min. The temperature of the glass plate was measured by installing a radiation thermometer immediately before blowing the gas. The etching time was 6.8 seconds.

<Examples 2 to 23 and Comparative Examples 2 to 5>
A glass plate was obtained in the same manner as in Example 1 except that the same glass material as in Example 1 was used and the HF concentration to be brought into contact with the glass plate and / or the temperature of the glass plate was changed to the conditions described in Table 1.
<Comparative Example 1>
An untreated glass plate not subjected to HF treatment was used as Comparative Example 1.

Table 1 shows test conditions (HF treatment conditions) and analysis results of the glass plates of Examples 1 to 23 and Comparative Examples 1 to 5. Moreover, the SEM photograph of the glass plate surface of Example 10 is shown in FIG. 2, and the SEM photograph of a glass plate cross section is shown in FIG.
In the table, the total contact amount of HF [mol / cm ² ] is a value obtained by hydrogen fluoride concentration (% by volume) / 100 × gas flow rate (mol / second / cm ² ) × treatment time 6.8 (second). is there.
“O” in “B ≦ G” means that in <spectral measurement 1> where the incident angle is 0 °, the average reflectance in the B region is equal to or less than the average reflectance in the G region. “X” means that the average reflectance in the B region is higher than the average reflectance in the G region.
“O” in “B ≦ R” means that in <spectral measurement 1> in which the incident angle is 0 °, the average reflectance in the B region is equal to or less than the average reflectance in the R region. “X” means that the average reflectance in the B region is higher than the average reflectance in the R region.
“O” indicates that the reflectance at an incident angle of 42 ° is 0.2% or less is an average value of the reflectance of one side of light having a wavelength of 400 to 700 nm in spectroscopic measurement 2 with an incident angle of 42 °. It means 0.20% or less, and “x” means that the average value of the reflectance is higher than 0.20%.
Regarding “thickness of uneven layer / nm”, “◯” was given to the range of the corresponding thickness.

  According to the present invention, a glass plate for a light guide plate having high luminance can be obtained. By using the glass plate as a light guide plate for a display such as a television, an improvement in image quality is expected, a load on a device such as a television is small, and an energy saving effect is also expected. Furthermore, depending on the uneven shape on the surface of the glass plate, color control for preventing yellowing can be unnecessary or minimized.

1 Central slit 2 Outer slit 4 Flow path 5 Exhaust slit 10 Injector 20 Glass plate

Claims (4)

At least one surface has irregularities, and in the spectroscopic measurement, the average reflectance of the surface of light having a wavelength of 400 to 700 nm at an incident angle of 0 ° is 4.0% or less, and iron converted into Fe ₂ O ₃ is used. the total amount is 1 mass ppm or more and 80 mass ppm or less, and ^_Fe 2 _{O 3 Fe} ²⁺ in terms of is less than 10 ppm by mass, the light guide plate glass plate.   In the spectroscopic measurement, the average value R of the reflectance of the surface of light having a wavelength of 600 to 650 nm, the average value G of the reflectance of the surface of light having a wavelength of 500 to 600 nm, and a wavelength of 430 to 460 nm at an incident angle of 0 °. 2. The glass plate for a light guide plate according to claim 1, wherein an average value B of the reflectance of the surface of light satisfies a relationship of an average value B ≦ average value R and an average value B ≦ average value G. 3.   3. The glass plate for a light guide plate according to claim 1, wherein an average value of the reflectance of the surface of light having a wavelength of 400 to 700 nm at an incident angle of 42 ° is 0.20% or less in spectroscopic measurement. A method for producing the glass plate for a light guide plate according to any one of claims 1 to 3,
Including a step of bringing a fluorine-containing gas into contact with the glass plate,
The manufacturing method of the glass plate for light-guide plates whose total contact amount to the said glass plate of the said fluorine-containing gas is 3.0 * 10 < ^-4 > mol / cm < ² > or more in conversion of a fluorine element.