WO2018101220A1

WO2018101220A1 - Glass plate

Info

Publication number: WO2018101220A1
Application number: PCT/JP2017/042456
Authority: WO
Inventors: 貴人梶原; 和田　直哉
Original assignee: 旭硝子株式会社
Priority date: 2016-12-01
Filing date: 2017-11-27
Publication date: 2018-06-07

Abstract

The purpose of the present invention is to provide a glass plate which has a higher internal transmittance of light having a wavelength of about 450 nm, than a conventional glass plate for a light guide plate, and which has optical characteristics suited to a quantum dot display using a blue LED. The present invention pertains to a glass plate containing less than 80 ppm by mass of total iron oxide (t-Fe₂O₃) in terms of Fe₂O₃, and more than 0 but less than 1.0 ppm by mass of NiO, more than 0 but less than 1.0 ppm by mass of Cr₂O₃, and more than 0 but not more than 5.0 ppm by mass of MnO₂ on an oxide basis, wherein the proportion of divalent iron (Fe²⁺) in terms of Fe₂O₃ in the total iron oxide in terms of Fe₂O₃ is more than 30%, when expressed as percent by mass.

Description

Glass plate

The present invention relates to a glass plate that can be used for a light guide plate, and more particularly to a glass plate suitable for a light guide plate used for a quantum dot display using a blue LED.

In recent years, with the increase in brightness, image quality, and power saving of thin display devices such as liquid crystal televisions, quantum dot displays using blue LEDs have been studied from displays using conventional white LEDs (for example, Patent Document 1).

In a quantum dot display, white light obtained by combining a blue LED as a blue light source and photoluminescence of quantum dots excited by a blue LED as a green / red light source is used as a backlight of a liquid crystal display.

As a method of arranging quantum dots in the backlight unit, there is mainly an edge light method in which a quantum dot assembly in which quantum dots are dispersed in a resin and sealed in a glass tube is arranged between a light source and a light guide plate.

An acrylic plate is widely used as the edge light type light guide plate, but replacement with a glass plate is under consideration from the viewpoint of rigidity, heat resistance or water resistance. For example, Patent Document 2 discloses glass suitable for a light guide of an edge light type planar light emitting device.

Japanese Unexamined Patent Publication No. 2008-10556 International Publication No. 2016/159362

As a result of investigations by the present inventors, it has been found that the following problems (1) to (3) are present from the viewpoint of the use of a quantum dot display using a blue LED.
(1) When a blue LED having a high output (for example, 110,000 Lx at a distance of 50 mm from the LED chip) is used as a light source, a conventional light guide plate made of resin is insufficient in heat resistance.
(2) In the conventional glass for light guide plates corresponding to white LED, the internal transmittance | permeability of the light in 450 nm vicinity which is the light emission wavelength range of blue LED is insufficient.
(3) When a conventional glass is irradiated with a high-intensity blue LED having an emission wavelength near 450 nm, the internal transmittance of light in the visible range is insufficient.

In view of the above problems, the present invention has an object to provide a glass plate having a high internal transmittance of light in the vicinity of a wavelength of 450 nm, which is suitable for a quantum dot display using a blue LED, as compared with a conventional glass plate for a light guide plate. And

As a result of intensive studies, the present inventors have found that the above problem can be solved by setting the composition range to a specific range, and have completed the present invention.

That is, the present invention, the total iron oxide in terms of _Fe 2 _{O 3} and _(t-Fe 2 _{O 3)} containing less than 80 mass ppm, on an oxide basis, the NiO less than 0 1.0 mass ppm, _Cr 2 O _There is provided a glass plate containing ₃ in excess of 0 and less than 1.0 ppm by mass, MnO ₂ in excess of 0 to 5.0 ppm by mass, and iron redox exceeding 30%.

By having a specific composition range, the glass plate of the present invention emits a blue LED having a high internal transmittance of light in the vicinity of a wavelength of 450 nm and a high luminance as compared with a conventional glass plate for a light guide plate. The reduction of visible internal transmittance due to is reduced. In addition, it has the same optical characteristics as a conventional resin light guide plate, and at the same time has heat resistance enough to withstand high-power blue LEDs. Therefore, the glass plate of this invention is suitable as a glass plate for light-guide plates used for the quantum dot display using blue LED.

FIG. 1 is a schematic view of the glass plate and blue LED illumination installation conditions when viewed from above, as viewed from above. FIG. 2 is an example of the spectrum of a blue LED. FIG. 3 is a diagram showing the influence of visible light solarization [difference in average absorbance] by blue LED irradiation due to the amount of MnO ₂ in the glass composition.

Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the gist of the present invention. In the present specification, “to” indicating a numerical range is used in the sense of including the numerical values described before and after the numerical value as a lower limit value and an upper limit value. In the present specification, “substantially not contained” means that it is not contained except for inevitable impurities, and specifically means that it is below the detection limit when measured by fluorescent X-ray analysis.

[Glass composition]
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 the mass percentage based on oxide or mass ppm (mass) Percentage is simply expressed as%, or mass ppm may be expressed as simply ppm).

The glasses according to the invention, the total iron oxide in terms of _Fe 2 _{O 3} and _(t-Fe 2 _{O 3)} containing less than 80 mass ppm, on an oxide basis, the NiO less than 0 1.0 mass ppm, Cr ₂ O ₃ is contained more than 0 and less than 1.0 ppm by mass, MnO ₂ is contained from 0 to 5.0 ppm by mass, and iron redox is more than 30%.

The main factor of light absorption of glass 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. In order to obtain a glass suitable for an application having a long optical path length inside the glass such as a light guide plate for edge light, it is preferable to reduce the total iron content in the glass composition and suppress light absorption by iron ions.

Accordingly, the content of total iron oxide in terms of _{_{_{Fe 2 O 3 (t-Fe}}} 2 O 3) is less than 80 ppm by weight, preferably 70 mass ppm or less, more preferably 60 mass ppm or less, more preferably 50 ppm by mass or less, more preferably 40 ppm by mass or less, particularly preferably 30 ppm by mass or less, and most preferably 25 ppm by mass or less.

On the other hand, the content of t-Fe ₂ O ₃ is preferably 5 ppm by mass or more in order to suppress the cost of the glass raw material, ensure the solubility of the glass, and prevent the infrared absorption of the glass from being extremely deteriorated. More preferably, it is 8 mass ppm or more, More preferably, it is 10 mass ppm or more, Especially preferably, it is 12 mass ppm or more, Most preferably, it is 15 mass ppm or more. The content of t-Fe ₂ O _{3 in} the glass can be adjusted by the amount of iron component added during glass production.

The iron ion takes the form of divalent iron (Fe ²⁺ ) and trivalent iron (Fe ³⁺ ) in the glass (hereinafter, these are collectively referred to as “iron component”). The iron component has absorption in the visible region, trivalent iron has an absorption peak near a wavelength of 450 nm, and divalent iron has an absorption peak near a wavelength of 1100 nm.

The decrease in the internal transmittance of light in the vicinity of 450 nm, which is the emission wavelength region of the blue LED, affects the luminance. Also, part of the white light obtained by exciting the quantum dots with blue LED light returns to the glass and re-enters as light. Therefore, when the internal transmittance of light decreases in a wavelength region other than the vicinity of 450 nm, when this return light re-enters the glass, light absorption increases, causing color unevenness, and there is a concern that a preferable color balance may be lost as a whole. is there.

The glass according to the present invention has an iron redox of more than 30%, preferably 32% or more, more preferably 34% or more, still more preferably 36% or more, particularly preferably 38% or more, and most preferably 40% or more. is there.

By making the iron redox more than 30%, the ratio of trivalent iron having an absorption peak in the vicinity of a wavelength of 450 nm is lowered, and the internal transmittance of light in the blue, particularly in the vicinity of a wavelength of 450 nm is improved, and a blue LED is used. Optical characteristics suitable for a quantum dot display can be obtained. Examples of methods for increasing iron redox include dissolution at high temperatures and the use of reducing agents such as tin oxide or coke.

In addition, on the long wavelength side in the visible region, particularly on the long wavelength side near the wavelength of about 600 nm, the internal transmittance is decreased, and there is a concern that the preferable color balance as a whole may be lost as described above. In the case of glass containing SO ₃ , sulfur (S) becomes negative divalent sulfur when dissolved in a reducing atmosphere in order to increase iron redox. As a result, it reacts with plus divalent iron in the glass to cause amber coloration, and the transmittance near 450 nm may be lowered. Therefore, the iron redox is preferably 70% or less, more preferably 65% or less, further preferably 60% or less, particularly preferably 55% or less, and most preferably 50% or less.

Iron redox is the ratio of divalent iron which in terms of _Fe 2 _{O 3} in the total iron oxide in terms of _Fe 2 _{O 3} ^{(Fe 2+),} obtained by the following equation (1).

Iron redox (%) = [[content of divalent iron (Fe ²⁺ ) converted to Fe ₂ O ₃ (mass ppm)] / [divalent iron (Fe ²⁺ ) converted to Fe ₂ O ₃ and trivalent iron Total content of (Fe ³⁺ ) (mass ppm)]] × 100 Formula (1)

The amount of divalent iron (Fe ²⁺ ) converted to Fe ₂ O ₃ is 3 mass ppm or more based on oxides in order to increase the heat ray absorption efficiency of the glass melt and improve the solubility when the glass raw material is melted. More preferably, it is 5 mass ppm or more, More preferably, it is 6 mass ppm or more, Most preferably, it is 7 mass ppm or more. Further, the upper limit is preferably 40 ppm by mass or less, more preferably 30 masses in order to increase the internal transmittance in the visible range, to reduce divalent iron that reacts with minus divalent sulfur, and to suppress amber color development. ppm or less, more preferably 20 mass ppm or less, particularly preferably 15 mass ppm or less, and particularly preferably 12 mass ppm or less.

The amount of trivalent iron (Fe ³⁺ ) converted to Fe ₂ O ₃ reduces the transmittance in the ultraviolet light region (UV light region), suppresses UV solarization when containing CeO ₂ described later, Since it has the effect of suppressing the generation of structural defects and suppressing the decrease in transmittance in the visible range, it is more than 5 ppm and less than 40 ppm on an oxide basis. The amount of iron oxide converted to Fe ₂ O ₃ is preferably 6 mass ppm or more, more preferably 7 mass ppm or more, still more preferably 8 mass ppm or more, and particularly preferably 9 mass ppm or more. The upper limit is preferably 38 mass ppm or less, more preferably 30 mass ppm or less, still more preferably 20 mass ppm or less, and particularly preferably 15 mass ppm or less, in order to suppress absorption in the vicinity of a wavelength of 450 nm. And most preferably 13 ppm by mass or less.

Nickel (hereinafter also referred to as Ni) has an absorption in the near-infrared region with a wavelength of 800 to 1100 nm, similar to Fe ^2+, and thus improves the heat ray absorption efficiency of the glass melt during glass melting. Therefore, by including Ni in the glass, the solubility of the glass can be improved even if the proportion of Fe ^{2+ in} the glass is small.

In addition, when a sulfur component enters during the glass melting process or glass forming process, the sulfur component is combined with Fe in the glass, iron sulfide is generated, causing coloration and reducing internal transmittance. When the Ni component is present in the glass, nickel sulfide can be selectively formed to suppress the formation of the iron sulfide, thereby reducing the coloration and maintaining the high internal transmittance of the glass.

For the above reasons, the content of oxide-based NiO is more than 0, preferably 0.05 mass ppm or more, more preferably 0.1 mass ppm or more, still more preferably 0.15 mass ppm or more, particularly preferably. It is 0.2 mass ppm or more.

On the other hand, Ni has absorption near wavelengths of 450 nm and 630 nm, and at the same time, the transmittance of the wavelength of 450 nm is lowered. Become one. Therefore, the content of oxide-based NiO is less than 1 ppm by mass, preferably 0.8 ppm by mass or less, more preferably 0.6 ppm by mass or less, and still more preferably 0.4 ppm by mass or less, Especially preferably, it is 0.3 mass ppm or less.

Chromium (hereinafter also referred to as Cr) can act as an oxidizing agent to control iron redox. The content of oxide-based Cr ₂ O ₃ is more than 0, preferably 0.05 mass ppm or more, more preferably 0.1 mass ppm or more, still more preferably 0.15 mass ppm or more, particularly preferably 0. .2 mass ppm or more.

Cr, like Ni, has absorption near wavelengths of 450 nm and 630 nm, and lowers the transmittance at a wavelength of 450 nm. At the same time, when the above-mentioned return light re-enters the glass, it becomes one of the factors that increase light absorption and cause color unevenness. Therefore, the content of oxide-based Cr ₂ O ₃ is less than 1.0 mass ppm, preferably 0.8 mass ppm or less, more preferably 0.6 mass ppm or less, and even more preferably 0.5 ppm. The mass ppm or less, particularly preferably 0.4 mass ppm or less, and most preferably 0.35 mass ppm or less.

The total amount of NiO and Cr ₂ O ₃ is preferably 1.5 mass ppm or less, more preferably 1.3 mass ppm or less, in order to suppress a decrease in transmittance at a wavelength of 450 nm and color unevenness due to the return light described above. Preferably it is 1.0 mass ppm or less, Most preferably, it is 0.7 mass ppm or less.

Manganese (hereinafter also referred to as Mn) acts as an oxidizing agent in order to suppress the refining cost of the raw material, and in order to adjust iron redox, the content of oxide-based MnO ₂ is more than 0, preferably 0 0.01 mass ppm or more, more preferably 0.05 mass ppm or more, still more preferably 0.1 mass ppm or more, particularly preferably 0.15 mass ppm or more, and most preferably 0.2 mass ppm or more.

Mn has absorption in the visible light region and emits electrons when irradiated with a blue LED. When the electrons react with titanium in the glass (hereinafter also referred to as Ti), light absorption by Ti is large. And may cause visible light solarization that reduces internal transmittance. For this reason, the fall of internal transmittance can be controlled by reducing the content of Mn. Note that “visible light solarization” in the present specification indicates a change in transmittance before and after irradiation with light having a wavelength of about 450 nm. Examples of the light source include white LEDs and blue LEDs.

Therefore, the content of MnO ₂ is 5.0 mass ppm or less, preferably 4.0 mass ppm or less, more preferably 3.0 mass ppm or less, still more preferably 2.0 mass ppm or less. Preferably it is 1.5 mass ppm, Most preferably, it is 1.0 mass ppm or less, Most preferably, it is 0.5 mass ppm or less.

In addition to NiO, Cr ₂ O ₃ and MnO ₂ , at least selected from the group consisting of CoO, V ₂ O ₅ , SeO _2, and CuO having the same characteristic of absorbing light in the wavelength range from the ultraviolet region to the near infrared region One kind of component may be included. Since these components function as components that absorb visible light, even if they contain at least one component selected from the group consisting of CoO, V ₂ O ₅ , SeO ₂ and CuO, the content thereof Is preferably 10 ppm by mass or less, more preferably 1 ppm by mass or less based on the oxide. From the viewpoint of not reducing the internal transmittance at a wavelength of 400 to 700 nm, it is preferable that at least one component selected from the group consisting of CoO, V ₂ O ₅ , SeO ₂ and CuO is not substantially contained.

In addition to the above, Yb ₂ O ₃ and Er ₂ O ₃ can also be contained because they have the property of absorbing light in the wavelength range from the ultraviolet region to the near infrared region. However, these components have a high rare value and greatly affect the production cost. Even in the case of containing these, the content is preferably 10 ppm by mass or less, more preferably 1 ppm by mass or less, and preferably substantially not contained, based on the oxide.

In addition, when Ti is contained in the glass as described above, visible light solarization is caused, light absorption by Ti is increased, and internal transmittance can be reduced. Accordingly, the content of TiO ₂ is preferably less than 40 ppm by mass, more preferably 30 ppm by mass or less, still more preferably 20 ppm by mass or less, and particularly preferably 10 ppm by mass or less.

Further, since Ti is a component that absorbs UV light, it has an effect of suppressing UV solarization described later. The content of TiO ₂ is preferably more than 0, more preferably 1 ppm by mass or more, further preferably 3 ppm by mass or more, and particularly preferably 5 ppm by mass or more.

The composition of the glass according to the present invention is not particularly limited as long as it has the above-described characteristics. Typical examples of preferred compositions for the mother composition are shown below.

Glass composition A: SiO ₂ is 60 to 85%, Al ₂ O ₃ is 0 to 10%, MgO is 0 to 10%, CaO is 0 to 20%, and SrO is 0 to 15 in terms of mass percentage based on oxide. %, BaO 0 to 15%, Na ₂ O 2 to 20%, K ₂ O 0 to 10% and B ₂ O ₃ 0 to 20%.
Glass composition B: SiO ₂ 45 to 80%, Al ₂ O ₃ more than 10% and 30% or less, B ₂ O ₃ 0 to 15%, MgO 0 to 15% in terms of mass percentage based on oxide the CaO 0 ~ 6%, the SrO 0 ~ 5%, a BaO 0 ~ 5%, 2 ~ 20% of Na ₂ O, the _{K 2} O 0-10%, a ZrO ₂ containing 0-10%.
Glass composition C: SiO ₂ 45-70%, Al ₂ O ₃ 10-30%, B ₂ O ₃ 0-15% in terms of mass percentage on oxide basis, MgO, CaO, SrO and BaO A total of 5 to 30% of at least one component selected from the group consisting of: and at least one component selected from the group consisting of Li ₂ O, Na ₂ O and K ₂ O Contain less than%.
Glass composition D: SiO ₂ 50-85%, Al ₂ O ₃ 0-20%, B ₂ O ₃ 0-10%, Na ₂ O 1-20% and expressed as a percentage by mass on an oxide basis It contains 0 to 20% or less of K ₂ O.

SiO ₂ is the 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 62% or more, and still more preferably 63% or more in the glass composition B. Is preferably 45% or more, more preferably 50% or more, still more preferably 55% or more, still more preferably 60% or more. In the glass composition C, preferably 45% or more, more preferably 50% or more. In the glass composition D, it is preferably 50% or more, more preferably 60% or more, and further preferably 65% or more. On the other hand, from the viewpoint of facilitating dissolution and improving the foam quality, the content of SiO _{2 in} the glass composition A is preferably 85% or less, more preferably 80% or less, and even more preferably 75% or less. More preferably, it is 72% or less, particularly preferably 68% or less. In the glass composition B, it is preferably 80% or less, more preferably 75% or less, still more preferably 70% or less, and the glass composition C Is preferably 70% or less, more preferably 65% or less. In the glass composition D, it is preferably 85% or less, more preferably 80% or less, and even more preferably 75% or less.

When the content of Al ₂ O ₃ increases, the viscosity at the time of dissolution increases, and there is a possibility that bubbles are difficult to escape. Therefore, in the glass composition A, the content of Al ₂ O ₃ is preferably 10% or less, more preferably 9% or less, still more preferably 8% or less, still more preferably 7% or less, and particularly preferably 6% or less. In the glass composition B, it is preferably 30% or less, more preferably 25% or less, still more preferably 23% or less, still more preferably 20% or less, and particularly preferably 15% or less. Yes, in the glass composition C, preferably 30% or less, more preferably 20% or less, and in the glass composition D, preferably 20% or less, more preferably 12% or less, even more preferably 10% or less, particularly Preferably it is 7.5% or less.

On the other hand, Al ₂ O ₃ is an essential component for improving the weather resistance of glass in the glass compositions B and C due to the effect of reducing non-crosslinked oxygen in the glass. In order to maintain the practically required weather resistance in the glass of the present invention, the content of Al ₂ O _{3 in} the glass composition A is preferably 0% or more, more preferably 0.5% or more, even more preferably. Is 1% or more, more preferably 2% or more, particularly preferably 2.5% or more. In the glass composition B, preferably more than 10%, more preferably 11% or more, and further preferably 12% or more. More preferably, it is 13% or more. In the glass composition C, it is preferably 10% or more, more preferably 13% or more. In the glass composition D, it is preferably 0% or more, more preferably 0.5%. More preferably, it is 1% or more, more preferably 2% or more, and particularly preferably 2.5% or more. In the glass, most of Al ₂ O ₃ exists in the form of tetracoordinate ([AlO ₄ ] ⁻ ), and binds to alkali metal ions such as Na ⁺ . Therefore, the number of alkali metal ions bonded to tetracoordinate iron ([FeO ₄ ] ⁻ , that is, Fe ³⁺ ) is reduced, and the ratio of Fe ³⁺ is reduced. As a result, the ratio of Fe ²⁺ can be increased, that is, the iron redox can be increased, and the internal transmittance of light in the vicinity of a wavelength of 450 nm can be improved.

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) The content of B ₂ O ₃ is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. More preferably, it is 3% or less, and most preferably it does not contain substantially. Further, in the glass composition B, it is preferably 15% or less, more preferably 12% or less, more preferably 10% or less, still more preferably 7% or less, and particularly preferably 4% or less, and is not substantially contained. Is most preferred. In the glass composition C, the content of B ₂ O ₃ is preferably 15% or less, more preferably 12% or less. In the glass composition D, the content is preferably 10% or less, more preferably 7% or less, even more preferably. Is most preferably 4% or less and substantially not contained.

Alkali metal oxides such as Na ₂ O, K ₂ O, and Li ₂ O are useful components for accelerating melting of the glass raw material and adjusting thermal expansion or viscosity. The total content of these components is preferably 2% or more, more preferably 3% in the glass compositions A and B in order to maintain the clarity when melted and to maintain the foam quality of the glass to be produced. More preferably, it is 5% or more, more preferably 8% or more. In the glass composition D, it is preferably 5% or more, more preferably 8% or more, and particularly preferably 10% or more. Further, in order to keep the coefficient of thermal expansion low and to improve the devitrification property, in the glass compositions A and B, it is preferably 20% or less, more preferably 15% or less, and in the glass composition C, preferably Is 2% or less, more preferably 1% or less. In the glass composition D, it is preferably 25% or less, and more preferably 20% or less.

In the glass composition A, the content of Na ₂ O is preferably 2% or more, more preferably 3% or more, still more preferably 5% or more, still more preferably 8% or more, and particularly preferably 10% or more. In the glass composition B, it is preferably 2% or more, more preferably 3% or more, further preferably 5% or more, more preferably 8% or more, particularly preferably 10% or more. In the glass composition D, preferably It is preferably 1% or more, more preferably 5% or more, still more preferably 8% or more, and particularly 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% or less. In the glass composition C, it is preferably 3% or less, more preferably 1% or less, and in the glass composition D, it is preferably 20% or less, more preferably 15% or less.

Here, the ratio in mass percentage based on oxides of Na ₂ O and _{_{_{Al 2 O 3 (Na 2 O}}} / Al 2 O 3) is according to the glass composition in terms of weather resistance and the transmittance control when used as a light guide plate Are preferably controlled. In order to improve the weather resistance, (Na ₂ O / Al ₂ O ₃ ) is preferably 7 or less, more preferably 5 or less, even more preferably 3.5 or less, particularly in glass compositions A and D. In the glass composition B, which is preferably 2 or less, it is preferably 1.5 or less, more preferably 1 or less. On the other hand, (Na ₂ O / Al ₂ O ₃ ) is preferably 0.1 or more, and preferably 0.2 or more in order to facilitate iron redox control during production and control the transmittance. More preferably, it is more preferably 0.5 or more, and particularly preferably 1.0 or more.

K ₂ O is a component that contributes to weather resistance, but in order to maintain the devitrification properties of the glass, the content of K ₂ O is preferably 10% or less, more preferably 7% in the glass compositions A and B. Or less, more preferably 5% or less, even more preferably 2% or less, and may not be contained. In the glass composition C, preferably 2% or less, more preferably 1% or less, and in the glass composition D Preferably, it is 20% or less, more preferably 10% or less, still more preferably 5% or less, and particularly preferably 2% or less.

Li ₂ O is an optional component, but in order to facilitate vitrification, keep the iron content contained as an impurity derived from the raw material low, and keep the raw material cost low, in glass compositions A and B, Li ₂ O Is preferably 5% or less, more preferably 3% or less, even more preferably 2% or less, and even more preferably 1% or less. In the glass composition C, Li ₂ O can be contained 2% or less. In the glass composition D, the content is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less.

CeO ₂ has the effect of lowering the redox of iron, and when ultraviolet light (UV light) is irradiated onto the glass, Ce emits electrons, causing UV solarization that causes new absorption, and visible light. It also functions as a component that absorbs. Therefore, the content of CeO ₂ is preferably 200 ppm or less, more preferably 150 ppm or less, still more preferably 100 ppm or less, particularly preferably 50 ppm or less, and most preferably not substantially contained. In the case of adding CeO ₂ , the content is preferably 5 ppm or more, more preferably 10 ppm or more, from the viewpoint of facilitating suppression of variations in product characteristics and color variations during production.

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, there exists an effect | action which reduces specific gravity and makes a glass article hard to be wrinkled. On the other hand, MgO increases the coefficient of thermal expansion of the glass and may deteriorate the devitrification characteristics. In addition, since the ion radius of Mg ions is close to the ion radius of Fe ²⁺ ions, Mg ions occupy Fe ²⁺ ion sites, and the ratio of Fe ²⁺ may decrease, which may reduce iron redox. In order to increase the iron redox of the glass, lower the thermal expansion coefficient, and improve the devitrification properties, the glass composition A is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less. In the glass composition B, it is 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. In the glass composition D, it is preferably 10% or less, more preferably 8% or less, still more preferably 5% or less, and particularly preferably 3% or less.

CaO is a component that promotes melting of the glass raw material and adjusts viscosity, thermal expansion, etc., and may be contained. In order to obtain the above action, the content of CaO is preferably 3% or more, more preferably 5% or more in the glass composition A, and preferably 1% or more, more preferably in the glass composition D. Is 3% or more, more 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 In the glass composition D, it is preferably 15% or less, more preferably 12% or less, and further preferably 10% or less.

The glass of the present invention may contain SrO and BaO. These components, like MgO and CaO, are useful components for accelerating melting of the glass raw material and adjusting thermal expansion, viscosity, and the like.

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. However, the SrO content in the glass compositions A and C is preferably 15% or less, and more preferably 10% or less in order to keep the thermal expansion coefficient of the glass low and not deteriorate the weather resistance. In glass composition B, it is preferably 5% or less, more preferably 3% or less, and in glass composition D, it is preferably 15% or less, more preferably 12% or less, and even more preferably 10%. Hereinafter, it is particularly preferably 8% or less.

BaO, like SrO, has the effect of increasing the coefficient of thermal expansion and lowering the high temperature viscosity of the glass. In order to obtain the above effect, BaO can be contained. However, the BaO content in the glass compositions A and C is preferably 15% or less, and more preferably 10% or less, in order to keep the thermal expansion coefficient of the glass low and not deteriorate the weather resistance. In glass composition B, it is preferably 5% or less, more preferably 3% or less. In glass composition D, it is preferably 15% or less, more preferably 12% or less, and even more preferably 10% or less. Especially preferably, it is 8% or less. In order to adjust the viscosity in the glass compositions A and B, BaO may be contained in an amount of 1% or more, and more preferably 2% or more.

Further, the total content of these alkaline earth metal oxides (MgO, CaO, SrO and BaO) is preferably 10% or more in the glass composition A in order to lower the viscosity at the time of melting the glass and promote the melting. More preferably, it is 13% or more. In the glass composition B, it is 1% or more, more preferably 3% or more. In the glass composition C, it is preferably 5% or more, more preferably 10% or more. In composition D, it is preferably at least 5%, more preferably at least 8%, more preferably at least 12%, particularly preferably at least 13%. In order to keep the coefficient of thermal expansion low and to improve the devitrification property, the glass composition A is preferably 30% or less, more preferably 27% or less, and the glass composition B is preferably 15%. Or less, more preferably 10% or less, in the glass composition C, preferably 30% or less, more preferably 20% or less, and in the glass composition D, preferably 25% or less, more preferably 20% or less. More preferably, it is 18% or less, particularly preferably 17% or less.

In the composition of the glass according to the present invention, ZrO ₂ may be contained as an optional component in order to improve the heat resistance and surface hardness of the glass. When ZrO ₂ is contained, the content thereof is preferably 0.1% or more, more preferably 0.3% or more, and further preferably 0.5% or more in the glass composition D. However, from the standpoint of maintaining devitrification characteristics and maintaining low density, the content of ZrO ₂ is preferably 10% or less, more preferably 5% or less in the glass compositions A, B and C, and the glass composition D Is preferably 5% or less, more preferably 3% or less, and still more preferably 2% or less, and it is particularly preferable that it is not substantially contained. In any of the glass compositions A, B, C, and D, the glass is less likely to be devitrified if it is 10% or less.

The glass according to the present invention may contain SO ₃ as a fining agent. However, when SO ₃ is contained, amber coloring occurs as described above, and the transmittance near 450 nm may be reduced. Accordingly, when SO ₃ is contained, its content is preferably 0.5% or less. More preferably, it is 0.4% or less, More preferably, it is 0.3% or less, Most preferably, it is 0.25% or less. However, in order to obtain the effect as a fining agent, it is preferable that it is over 0%.

The glass according to the present invention may contain one or more of Sb ₂ O ₃ and As ₂ O ₃ as an oxidizing agent and a clarifying agent. In this case, the content of Sb ₂ O ₃ or As ₂ O ₃ is preferably 0 to 0.5%. 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 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 preferably not intentionally contained from the viewpoint of the environment. Since Sb ₂ O ₃ is colored in a reducing atmosphere and has the property of affecting the internal transmittance in the visible light region, it is preferably not intentionally contained.

The glass according to the present invention may contain tin oxide as a reducing agent as described above. Tin oxide also has an effect as a fining agent. Tin is present in the glass in a tetravalent and divalent state. When iron redox is low (for example, less than 30%), divalent tin acts as a reducing agent, and iron redox can be increased. On the other hand, when iron redox is high (for example, 70% or more), tetravalent tin acts as an oxidizing agent for iron. Moreover, since tin reduction occurs preferentially over sulfur reduction, amber coloration caused by sulfur reduction can be suppressed. When tin is contained, the content of total tin oxide converted to SnO ₂ is preferably 0.5% or less, more preferably 0.3% or less, and particularly preferably 0.2% or less.

The composition of the glass according to the present invention can be measured by the fluorescent X-ray method. Further, boron B, which is a light element and difficult to measure by the fluorescent X-ray method, and trace elements of 1000 ppm by mass or less can be measured by ICP emission spectroscopic analysis.

Moreover, when measuring the amount of divalent iron in the glass produced by the float method, the layer containing tin is polished by about 100 μm and then measured by the method described later. In addition, when measuring the amount of divalent iron in a glass containing tin oxide as an additive regardless of the production method, the amount of divalent iron and the transmittance at a wavelength of 800 to 1500 nm in a glass having the same composition containing no tin. The amount of divalent iron can be obtained from the spectroscopic analysis by clarifying the above relationship and creating a calibration curve.

[Internal transmittance]
In the glass plate according to the present invention, the average internal transmittance (α) of light having a wavelength of 420 to 470 nm at an optical path length of 50 mm is preferably 95% or more, more preferably 97.5% or more, and still more preferably 98%. Above, especially preferably 99% or more.

The average internal transmittance (alpha), the content of total iron oxide in terms of _{_{_{Fe 2 O 3 (t-Fe}}} 2 O 3), Ni, Cr content and Mn, in the range of iron redox, etc. of the composition It can be achieved by adjusting with. Specifically, for example, the content of t-Fe ₂ O ₃ is preferably 10 to 65 ppm by mass, the content of NiO is preferably 0.1 to 0.95 ppm by mass, and the content of Cr ₂ O ₃ is Preferably 0.1 to 0.95 mass ppm, the total amount of NiO and Cr ₂ O ₃ is 0.5 to 1.3 mass ppm, and the content of MnO ₂ is preferably 0.3 to 4.8 mass ppm Further, there is a method in which the iron redox is preferably more than 30% to 60%.

In the glass plate according to the present invention, the average internal transmittance (β) of light having a wavelength of 520 to 570 nm at an optical path length of 50 mm is preferably 90% or more, more preferably 95% or more, and still more preferably 98%. Above, especially preferably 99% or more.

The average internal transmittance (beta), the content of total iron oxide in terms of _{_{_{Fe 2 O 3 (t-Fe}}} 2 O 3), Ni, Cr content and Mn, in the range of iron redox, etc. of the composition It can be achieved by adjusting with. Specifically, for example, the content of t-Fe ₂ O ₃ is preferably 10 to 65 ppm by mass, the content of NiO is preferably 0.1 to 0.95 ppm by mass, and the content of Cr ₂ O ₃ is Preferably 0.1 to 0.95 mass ppm, the total amount of NiO and Cr ₂ O ₃ is 0.5 to 1.3 mass ppm, and the content of MnO ₂ is preferably 0.3 to 4.8 mass ppm Further, there is a method in which the iron redox is preferably more than 30% to 60%.

Furthermore, the average internal transmittance (γ) of light having a wavelength of 675 to 725 nm at an optical path length of 50 mm is preferably 70% or more, more preferably 80% or more, still more preferably 90% or more, and still more preferably 93 % Or more, particularly preferably 95% or more.

The average internal transmittance (gamma), the content of total iron oxide in terms of _{_{_{Fe 2 O 3 (t-Fe}}} 2 O 3), Ni, Cr content and Mn, in the range of iron redox, etc. of the composition It can be achieved by adjusting with. Specifically, for example, the content of t-Fe ₂ O ₃ is preferably 10 to 65 ppm by mass, the content of NiO is preferably 0.1 to 0.95 ppm by mass, and the content of Cr ₂ O ₃ is Preferably 0.1 to 0.95 mass ppm, the total amount of NiO and Cr ₂ O ₃ is 0.5 to 1.3 mass ppm, and the content of MnO ₂ is preferably 0.3 to 4.8 mass ppm Further, there is a method in which the iron redox is preferably more than 30% to 60%.

Measure the average internal transmittance according to the following procedure. First, a sample having a size of 50 mm in length and 50 mm in width is collected by cleaving from a substantially central portion of a target glass plate in a direction perpendicular to the first main surface of the glass plate.

Next, the arithmetic average roughness Ra of the first and second fractured surfaces facing each other of this sample is set to 0.03 μm or less. When the arithmetic average roughness Ra is larger than 0.03 μm, the first and second fractured surfaces are polished with free abrasive grains of colloidal silica or cerium oxide.

Next, in the sample A, the first fractured face, the normal direction of the first split section, at 50mm length, measuring the transmittance T _A in the measurement wavelength range. In the measurement of the transmittance T _A, 50 mm spectrometer capable of measuring in length (e.g., UH4150: Hitachi High-Technologies Corporation) was used, the slit or the like, smaller than the thickness of the beam width of the incident light And measure.

Next, the g-line (435.8 nm), F-line (486.1 nm), e-line (546.1 nm), d-line (587.6 nm), C-line (656.3 nm) of sample A by the V-block method. ) Is measured at room temperature with a precision refractometer.

Each coefficient B ₁ , B ₂ , B ₃ , C ₁ , C ₂ , C ₃ of the Sellmeier dispersion formula [formula (I) below] is determined by the least square method so as to fit the refractive index value. To obtain the refractive index n _A of sample A:

n _A = [1+ {B ₁ λ ² / (λ ² −C ₁ )} + {B ₂ λ ² / (λ ² −C ₂ )} + {B ₃ λ ² / (λ ² −C ₃ )}] ^0.5 Formula (I) In formula (I), λ is a wavelength.

The reflectance R _A at the first and second fractured surfaces of the sample A is determined by the following theoretical formula [formula (II)]:
R _A = (1-n _A ) ² / (1 + n _A ) ² (II) Formula

Next, with reference to formula (III) below, from the transmittance T _A at 50mm length sample A, by excluding the influence of reflection, the sample A, from the first split section in the normal direction Obtain the internal transmittance T _in at 50 mm length:
T _in = [− (1−R _A ) ² + {(1−R _A ) ⁴ + 4T _A ² R _A ² } ^0.5 ]
/ (2T _A R _A ² ) (III) Formula

By averaging the internal transmittance T _in obtained at each wavelength over the measurement wavelength range, the average internal transmittance of the glass plate T _ave is calculated.

[Average internal transmittance after LED irradiation]
In the glass plate according to the present invention, the average internal transmittance (α) of light having a wavelength of 420 to 470 nm at an optical path length of 50 mm after irradiating the LED under the following conditions is preferably 95% or more, more preferably 96% or more. More preferably, it is 97% or more, particularly preferably 98% or more, and most preferably 98.5% or more. When the average internal transmittance (α) after irradiation with the high-intensity blue LED is 95% or more, it is possible to suppress a decrease in luminance and unevenness in color of the display device.

(Condition) Directly attach one side of the following glass plate to the following blue LED illumination, adjust the position so that all the light from the LED enters from the end face of the glass plate, and then irradiate the glass plate for 21 hours To do.
Blue LED illumination: Illumination in which blue LED chips with a size of 1 mm square that emit light at a central wavelength of 453 nm are arranged in a line at intervals of 0.2 mm. The length of the line is 50 mm. The illuminance at a distance of 20 mm from the LED chip when no sample is placed is 200,000 Lx.
Glass plate: A glass plate having a rectangular parallelepiped shape with a main surface size of 50 mm square and a thickness of 1.8 mm, and having a main surface and end surfaces mirror-polished. In addition, as an example of the LED irradiation device, an ultra-high brightness linear illumination, LLRG500WB, manufactured by ITEC System Co., Ltd. can be mentioned. FIG. 1 shows a schematic view seen from above with respect to the installation conditions of the blue LED illumination 3 in which the glass plate 1 and the blue LED chip 2 are arranged in a line at the time of LED irradiation.

As a method of setting the average internal transmittance (α) after LED irradiation to 95% or more under the above conditions, for example, the content of MnO ₂ is preferably 0.2 to 4.8 mass ppm, and the content of TiO ₂ is Preferably more than 0 to less than 40 ppm by mass, t-Fe ₂ O ₃ content is preferably 10 to 65 ppm by mass, NiO content is preferably 0.1 to 0.95 ppm by mass, Cr ₂ O ₃ A method in which the content is preferably 0.1 to 0.95 mass ppm and the total amount of NiO and Cr ₂ O ₃ is 0.5 to 1.3 ppm by mass can be mentioned.

In the glass plate according to the present invention, the average internal transmittance (β) of light having a wavelength of 520 to 570 nm at an optical path length of 50 mm after irradiating the LED under the above conditions is preferably 90% or more, more preferably 92% or more. More preferably, it is 94% or more, particularly preferably 96% or more, and most preferably 98% or more. When the average internal transmittance (β) after irradiation with the high-intensity blue LED is 90% or more, deterioration of color unevenness of the display device can be suppressed.

As a method of setting the average internal transmittance (β) after LED irradiation to 90% or more under the above conditions, for example, the content of MnO ₂ is preferably 0.2 to 4.8 mass ppm, and the content of TiO ₂ is Preferably more than 0 to less than 40 ppm by mass, t-Fe ₂ O ₃ content is preferably 10 to 65 ppm by mass, NiO content is preferably 0.1 to 0.95 ppm by mass, Cr ₂ O ₃ A method in which the content is preferably 0.1 to 0.95 mass ppm and the total amount of NiO and Cr ₂ O ₃ is 0.5 to 1.3 ppm by mass can be mentioned.

The glass plate according to the present invention preferably has an average internal transmittance (γ) of light having a wavelength of 675 to 725 nm at an optical path length of 50 mm after irradiating the LED under the above conditions, preferably 70% or more, more preferably 80%. Or more, more preferably 90% or more, particularly preferably 92% or more, and most preferably 94% or more. When the average internal transmittance (γ) after irradiation with the high-intensity blue LED is 70% or more, the deterioration of the color unevenness of the display device can be suppressed.

As a method of setting the average internal transmittance (γ) after LED irradiation to 70% or more under the above conditions, for example, the content of MnO ₂ is preferably 0.2 to 4.8 mass ppm, and the content of TiO ₂ is Preferably more than 0 to less than 40 ppm by mass, t-Fe ₂ O ₃ content is preferably 10 to 65 ppm by mass, NiO content is preferably 0.1 to 0.95 ppm by mass, Cr ₂ O ₃ A method in which the content is preferably 0.1 to 0.95 mass ppm and the total amount of NiO and Cr ₂ O ₃ is 0.5 to 1.3 ppm by mass can be mentioned.

〔Production method〕
The glass plate of the present invention can be produced by a usual method. That is, after melting a glass raw material blended so that the composition of the glass to be produced has a desired composition by a conventional method to obtain a molten glass, the molten glass is subjected to a float method, a rollout method, a pulling method, Although a glass plate can be obtained by molding using a molding method such as a cold top method or a fusion method, it is more preferable that the glass plate is produced by a float method capable of large area and mass production.

[Use]
Examples of the glass plate include liquid crystal televisions, displays, light guide plates for in-vehicle liquid crystal display devices, solar cell covers and solar cell back sheets, and glass for architectural use such as window glass. Especially, since the internal transmittance | permeability of the light in the wavelength 450nm vicinity is high compared with the conventional light-guide plate, it is more preferable to use as a light-guide plate used for the quantum dot display using blue LED. It is also suitable as a light guide plate for a white LED light source with improved internal transmittance of light in the vicinity of 450 nm.

The size of the glass plate varies depending on the application, but at least one side is preferably 50 mm or more in length, and preferably 0.1 mm or more in thickness. For example, when the glass plate is used for a light guide plate of an edge-light type liquid crystal television, it is preferable that at least one side of the glass plate has a length of 200 mm or more. Moreover, it is preferable that the thickness of a glass plate is 0.1 mm or more, More preferably, it is 1 mm or more, More preferably, it is 1.8 mm or more. In use in this application, the thickness is preferably 3.0 mm or less in order to prevent an increase in weight. It is more preferably 2.6 mm or less, and further preferably 2.2 mm or less.

Further, when the glass plate is used for a light guide plate of an in-vehicle liquid crystal display device, the glass plate preferably has a length of at least one side of 50 mm or more. The thickness of the glass plate is preferably 1.0 mm or more, more preferably 1.5 mm or more, further preferably 2.0 mm or more, and preferably 10 mm or less.

Moreover, when using for architectural glass as a glass plate, it is preferable that the length of the glass plate is at least 50 mm or more, preferably 200 mm or more, more preferably 300 mm or more, and 500 mm or more. And particularly preferred. If the thickness of the glass plate is 1.0 mm or more, the rigidity is ensured, so that the glass plate is difficult to bend. When compared with acrylic, the glass plate is not only excellent in strength but also has a high-class feeling. The thickness may be appropriately selected from 1.8 mm or more, 2.0 mm or more, 2.5 mm or more, 3.5 mm or more, 6.0 mm or more, or 8.0 mm or more depending on the purpose.

As described above, although the preferred size and thickness differ depending on the application, the glass plate according to the present invention preferably has a length of at least one side of 50 mm or more and a thickness of 0.1 mm or more.

The glass plate according to the present invention may be subjected to a tempering treatment from the viewpoint of improving the strength. Examples of the strengthening method include air cooling strengthening treatment and chemical strengthening treatment.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Glass plate>
(Examples 1-18, 20-32)
The raw materials of each component were prepared so as to have a target composition, and were melted at a temperature of 1400 ° C. to 1700 ° C. for 3 to 10 hours using a platinum crucible. In the melting, 400 g of the raw material was added in three portions every 20 minutes, a platinum stirrer was inserted into the molten glass, and the mixture was stirred for 1 hour to homogenize the glass. Next, the molten glass was poured out and molded into a plate shape, and gradually cooled to room temperature at a cooling rate of 1 ° C. per minute to obtain a glass block. What is necessary is just to select suitably the particle size of a raw material, and the kind and quantity of a clarifying agent.

The particle size of the raw material is 1 to 1000 μm, the raw material types are cinnabar sand, aluminum oxide and sodium carbonate, the clarifier types are sulfate, tin oxide and nitrate, and the clarifier amount is 0.1 to 0.5 A mass% etc. can be illustrated.

Each component in the table is indicated by a mass percentage display based on oxide at a depth of 5000 nm or more from the surface of the glass plate.

(Example 19)
A sheet of 1.8 mm thickness and 50 mm square made of polymethyl methacrylate (PMMA) was prepared.

<Evaluation>
(Glass composition)
About the obtained glass block, the glass composition except boron B and an element of 1000 ppm by mass or less is used to identify the polished glass block by the fluorescent X-ray method using the RSX maker ZSX100e under the following measurement conditions. It was.

Polishing conditions: A part of the obtained glass block was cut, and the measurement surface was polished by 5 μm or more using a # 1000 grindstone.
・ Measurement conditions: tube voltage 50kV, measurement diameter 30mmφ

The method for measuring the B content in glass is shown below. An aqueous sodium hydroxide solution was added to the crushed glass and decomposed by heating, and then nitric acid was added to the decomposition solution to make an acidic solution. Ion exchange water was added to the acidic solution to make a certain amount, and the concentration of B was measured by ICP emission spectroscopy.

The concentration was calculated from a calibration curve prepared using a standard solution. The B content in the glass was calculated from the measured concentration and the amount of decomposition of the glass. Measurement was performed using SPS3100 manufactured by Hitachi High-Tech Science Co., Ltd. as an ICP emission photometer.

(T-Fe ₂ O ₃ content, Fe ²⁺ content, Fe ³⁺ content)
The total iron oxide amount (t-Fe ₂ O ₃ ) was measured as follows. The crushed glass was decomposed by adding a mixed acid of hydrofluoric acid and perchloric acid and heating. After decomposition, hydrochloric acid was added to make a certain amount, and the concentration of Fe was measured by ICP emission spectroscopy. The above-mentioned crushed glass was obtained by grinding a layer containing tin 100 μm after grinding.

Then, the concentration was calculated from a calibration curve prepared using the standard solution. From the measured concentration and the amount of decomposition of the glass, the content of t-Fe ₂ O _{3 in} the glass was calculated. Measurement was performed using SPS3100 manufactured by Hitachi High-Tech Science Co., Ltd. as an ICP emission photometer.

A method for measuring the Fe ²⁺ content is shown below. After the crushed glass is decomposed at room temperature with a mixed acid of hydrofluoric acid and hydrochloric acid, a certain amount of the decomposed solution is dispensed into a plastic container, and a 2,2′-dipyridyl solution and an ammonium acetate buffer solution are quickly added. As a result, only Fe ²⁺ was developed. The color developing solution was made constant with ion-exchanged water, and the absorbance at a wavelength of 522 nm was measured with an absorptiometer.

Then, the concentration was calculated from a calibration curve prepared using the standard solution. From this measured concentration and the amount of decomposition of the glass, the Fe ²⁺ content (mass ppm) in the glass converted to Fe ₂ O ₃ was calculated. As an absorptiometer, UV-1700 manufactured by Shimadzu Corporation was used.

The content (mass ppm) of Fe ³⁺ was calculated from the difference between the total iron oxide content determined above and the content of Fe ²⁺ as expressed by the following formula, and expressed in terms of Fe ₂ O ₃ .
Fe ³⁺ = (t-Fe ₂ O ₃ )-(Fe ²⁺ )

(Analyzing method of divalent iron in glass added with SnO ₂ )
In the glass added with SnO ₂ as an additive, the amount of divalent iron was determined by the following method. A plurality of glasses having the same composition and different amounts of divalent iron to which SnO ₂ was not added were prepared, and the amount of divalent iron was determined using the above method. Then, each glass was processed into a glass cuboid having a long side of 50.0 mm, a short side of 30.0 mm, and a thickness of 1.8 mm, and all surfaces were polished to a mirror surface. Light was transmitted in the direction of the long side of the prepared glass cuboid with a spectrophotometer, and the external transmittance T (λ) was measured.

The spectrophotometer used was a spectrophotometer UH4150 manufactured by Hitachi High-Technologies Corporation. At this time, a spectrophotometer was used in combination with a detector manufactured by the company that can measure long samples. External transmittance T (λ) at an optical path length of 50.0 mm was obtained at 1 nm intervals in the measurement wavelength range.

From the obtained measurement results, the wavelength having the lowest transmittance at a wavelength of 800 to 1300 nm was defined as the absorption peak position of divalent iron, and the absorbance was obtained from the following formula.
Absorbance: -Log (T / 100)

For each glass, the absorbance with respect to the amount of divalent iron was determined by the above method, and a calibration curve was prepared. The glass doped with SnO _2, determine the absorbance in the same manner, using a calibration curve prepared was determined divalent iron content.

(Ni, Cr, Mn and Ti amount)
The crushed glass was decomposed by adding a mixed acid of hydrofluoric acid and perchloric acid and heating. After decomposition, nitric acid was added to a constant amount, and the concentrations of Ni, Cr and Mn were measured by ICP mass spectrometry. Then, the concentration was calculated from a calibration curve prepared using the standard solution. Each content of Ni, Cr and Mn in the glass was calculated from the measured concentration and the amount of decomposition of the glass. The ICP mass spectrometer used was Agilent 8800 manufactured by Agilent Technologies. Ti was analyzed by ICP emission spectroscopy. Then, the concentration was calculated from a calibration curve prepared using the standard solution. In addition, the measurement using Hitachi High-Tech Science SPS3100 was performed as an ICP emission photometer.

(Internal transmittance in the visible range)
The internal transmittance in the measurement wavelength range of the obtained glass block was measured under the following measurement conditions using a spectrophotometer UH4150 manufactured by Hitachi High-Technologies Corporation.

The glass block was processed into a glass cuboid having a long side of 50.0 mm, the other side having a short side of 30.0 mm, and a thickness of 1.8 mm, and all surfaces were polished to a mirror surface. Light was transmitted in the direction of the long side of the prepared glass cuboid with a spectrophotometer, and the external transmittance T (λ) was measured. At this time, a spectrophotometer was used in combination with a detector manufactured by the company that can measure long samples. External transmittance T (λ) at an optical path length of 50.0 mm was obtained at 1 nm intervals in the measurement wavelength range.

Then, at least each wavelength of g line (435.8 nm), F line (486.1 nm), e line (546.1 nm), d line (587.6 nm), and C line (656.3 nm) of the glass cuboid The refractive index was measured by a precision refractometer KPR-2000 manufactured by Shimadzu Corporation by the V-block method, and each coefficient B ₁ , B ₂ of the Sellmeier's dispersion formula [Formula (I) below] B ₃ , C ₁ , C ₂ , C ₃ were determined by the least square method. Thereby, the refractive index n (λ) of the glass was obtained.

n (λ) = [1+ {B ₁ λ ² / (λ ² −C ₁ )} + {B ₂ λ ² / (λ ² −C ₂ )} + {B ₃ λ ² / (λ ² −C ₃ ) }] ^0.5 (I)

Based on the refractive index n (λ) obtained by the formula (I), the reflectance R (λ) of one side of the glass cuboid was obtained by the relational expression of the refractive index and the reflectance [the following formula (II)]. .

R (λ) = (n (λ) −1) ² / (n (λ) +1) ² (II)

Since the external transmittance T (λ) is a measured value affected by the surface reflection of the glass cuboid, it is necessary to exclude the influence of the surface reflection in order to obtain the internal transmittance U (λ). Therefore, the internal transmittance U (λ) at a length of 50.0 mm of the glass cuboid was determined by the following formula (III).

U (λ) = − [(1−R (λ)) ² + {(1−R (λ)) ⁴ + 4R (λ) ² T (λ) ² } ^0.5 ] / 2R (λ) ² T ( λ) (III)

(Average internal transmittance after LED irradiation)
Under the following conditions, the average internal transmittance of light in each wavelength region (420 to 470 nm, 520 to 570 nm, or 675 to 725 nm) at an optical path length of 50 mm after irradiation with the LED was examined. For each wavelength region, ΔT was determined by dividing the average internal transmittance after irradiation from the average internal transmittance before irradiation.
(Condition) Directly attach one side of the following glass plate to the following blue LED illumination (Ultra High Brightness Linear Illumination LLRG500WB manufactured by ITEC System) and adjust the position so that all the light from the LED is incident from the end face of the glass plate Then, the LED is irradiated on the glass plate for 21 hours.
Blue LED illumination: Illumination in which blue LED chips with a size of 1 mm square that emit light at a central wavelength of 453 nm are arranged in a line at intervals of 0.2 mm. The length of the line is 50 mm. The illuminance at a distance of 20 mm from the LED chip when no sample is placed is 200,000 Lx.
Glass plate: A glass plate having a rectangular parallelepiped shape with a main surface size of 50 mm square and a thickness of 1.8 mm, and having a main surface and end surfaces mirror-polished.

(State after LED irradiation)
The glass block of Example 12 was processed to a thickness of 1.8 mm and a 50 mm square, and the surface and end face were mirror-polished. Further, the polymethyl methacrylate film of Example 19 was used as a comparative example. The LED was irradiated to the glass plate of Example 12 and the film of Example 19 for 21 hours under the following conditions.
(Condition) Directly attach one side of a glass plate or film to the following blue LED illumination (Ultra High Brightness Linear Illumination LLRG500WB manufactured by ITEC System Co., Ltd.) so that all light from the LED is incident from the end face of the glass plate or film. After adjusting the position, the LED is irradiated on the glass plate or film for 21 hours.
Blue LED illumination: Illumination in which blue LED chips with a size of 1 mm square that emit light at a central wavelength of 453 nm are arranged in a line at intervals of 0.2 mm. The length of the line is 50 mm. The illuminance at a distance of 20 mm from the LED chip when no sample is placed is 200,000 Lx.

The state after LED irradiation was observed visually and evaluated according to the following criteria.
○: Cannot be melted by LED irradiation and can be used as a light guide plate.
X: It melt | dissolves by LED irradiation and cannot be used as a light-guide plate.

(Difference in average absorbance at wavelengths of 520 to 570 nm before and after LED irradiation)
For glass plates made of the glass of Examples 1, 5, 12 and 17, the average absorbance at wavelengths of 520 to 570 nm after irradiating the LED under the conditions described above in (Average internal transmittance after LED irradiation) is the wavelength before irradiation. The difference in average absorbance divided from the average absorbance at 520 to 570 nm was determined. The average absorbance at a wavelength of 520 to 570 nm is obtained by measuring the external transmittance with a spectrophotometer (Spectrum photometer UH4150 manufactured by Hitachi High-Technologies Corporation) at an optical path length of 50.0 mm, and converting it to the internal transmittance by the above method. It calculated | required from the obtained internal transmittance | permeability using following formula (IV).
Average absorbance at wavelengths of 520 to 570 nm = −Log (U (λ _{520 to 570} ) / 100) (IV)
Here, U (λ _{520 to 570} ) is an average internal transmittance at a wavelength of 520 to 570 nm.

The results are shown in Tables 1 to 5 and FIG. FIG. 3 is a diagram showing a correlation between the amount of MnO ₂ in the glass and the difference in average absorbance at wavelengths of 520 to 570 nm before and after the blue LED irradiation. Examples 3 to 16 and 20 to 32 are examples, and examples 1, 2, and 17 to 19 are comparative examples. In the table, “-” indicates that it has not been evaluated.

As shown in Tables 1 and 2, the internal transmittance of light in the vicinity of the wavelength of 450 nm of the glass plate of the example is equal to or greater than the internal transmittance of light in the vicinity of the wavelength of 450 nm of the comparative example, and the visible region after irradiation with the blue LED The decrease in internal transmittance was reduced. From this result, it was found that the glass of the present invention is suitable for a glass plate for a light guide plate of a quantum dot display using a blue LED.

As shown in Table 3 and FIG. 3, the amount of change in internal transmittance due to the irradiation of the blue LED is correlated with the amount of Mn contained in the glass, and the content of MnO ₂ contained in the glass is 5.0 mass ppm. It was found that the visible light solarization caused by the irradiation of the blue LED can be suppressed by lowering the following. Moreover, since the amount of change varies depending on the illuminance and irradiation time of the blue LED in the visible light solarization, for example, when the LED having lower illuminance than the LED of this test is used, the same applies depending on the irradiation time. Shows behavior.

As shown in Table 4, the glass plate of Example 12, which is an example, has high internal transmittance equivalent to that of the resin sheet of Example 19, which is a comparative example, and has heat resistance against irradiation of a blue LED. I found out. On the other hand, the resin-made sheet of Example 19 was deformed by heat due to the irradiation of the blue LED, and could not be used as a light guide plate using the blue LED as a light source.

The glass plate of the present invention has a high internal transmittance of light in the vicinity of a wavelength of 450 nm as compared with a conventional glass plate for a light guide plate, and a decrease in internal transmittance in the visible region by irradiating a high-intensity blue LED. Has been reduced. In addition, it has the same optical characteristics as a conventional resin light guide plate and has heat resistance that can withstand a high-power blue LED. Therefore, the glass plate of this invention can be used suitably as a glass plate for light guide plates, especially a glass plate for light guide plates used for a quantum dot display using a blue LED.

Although the invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application claims priority based on Japanese Patent Application No. 2016-234120 filed with the Japan Patent Office on December 1, 2016, and the entire contents of Japanese Patent Application No. 2016-234120 are incorporated herein by reference. .

1 Glass 2 Blue LED chip 3 Blue LED lighting

Claims

Total iron oxide in terms of Fe 2 O 3 and (t-Fe 2 O 3) containing less than 80 mass ppm,
On the oxide basis, it contains NiO more than 0 and less than 1.0 mass ppm, Cr 2 O 3 contains more than 0 and less than 1.0 mass ppm, MnO 2 contains more than 0 and 5.0 mass ppm, and iron redox is 30%. A glass plate that is super.
Glass plate according to claim 1 which contains less than the TiO 2 0 super 40 mass ppm on an oxide basis.
Oxide-based mass percentage display, SiO 2 50-85%, Al 2 O 3 0-20%, B 2 O 3 0-10%, Na 2 O 1-20% and K 2 O The glass plate according to claim 1 or 2, which contains 0 to 20% or less.
The glass plate according to any one of claims 1 to 3, wherein the average internal transmittance (α) of light having a wavelength of 420 to 470 nm at an optical path length of 50 mm is 95% or more.
The glass plate according to claim 4, wherein the average internal transmittance (β) of light having a wavelength of 520 to 570 nm at an optical path length of 50 mm is 90% or more.
6. The glass plate according to claim 4, wherein an average internal transmittance (γ) of light having a wavelength of 675 to 725 nm at an optical path length of 50 mm is 70% or more.
The glass plate according to any one of claims 1 to 6, wherein an average internal transmittance (α) of light having a wavelength of 420 to 470 nm at an optical path length of 50 mm after irradiation with a blue LED is 95% or more under the following conditions.
(Condition) Directly attach one side of the following glass plate to the following blue LED illumination, adjust the position so that all the light from the LED enters from the end face of the glass plate, and then irradiate the glass plate for 21 hours To do.
Blue LED illumination: Illumination in which blue LED chips with a size of 1 mm square that emit light at a central wavelength of 453 nm are arranged in a line at intervals of 0.2 mm. The length of the line is 50 mm. The illuminance at a distance of 20 mm from the LED chip when no sample is placed is 200,000 Lx.
Glass plate: A glass plate having a rectangular parallelepiped shape with a main surface size of 50 mm square and a thickness of 1.8 mm, and having a main surface and end surfaces mirror-polished.
The glass plate according to any one of claims 1 to 6, wherein an average internal transmittance (β) of light having a wavelength of 520 to 570 nm at an optical path length of 50 mm after irradiation with the LED is 90% or more under the following conditions.
(Condition) Directly attach one side of the following glass plate to the following blue LED illumination, adjust the position so that all the light from the LED enters from the end face of the glass plate, and then irradiate the glass plate for 21 hours To do.
Blue LED illumination: Illumination in which blue LED chips with a size of 1 mm square that emit light at a central wavelength of 453 nm are arranged in a line at intervals of 0.2 mm. The length of the line is 50 mm. The illuminance at a distance of 20 mm from the LED chip when no sample is placed is 200,000 Lx.
Glass plate: A glass plate having a rectangular parallelepiped shape with a main surface size of 50 mm square and a thickness of 1.8 mm, and having a main surface and end surfaces mirror-polished.
The glass plate according to any one of claims 1 to 6, wherein an average internal transmittance (γ) of light having a wavelength of 675 to 725 nm at an optical path length of 50 mm after irradiation with the LED is 70% or more under the following conditions.
(Condition) Directly attach one side of the following glass plate to the following blue LED illumination, adjust the position so that all the light from the LED enters from the end face of the glass plate, and then irradiate the glass plate for 21 hours To do.
Blue LED illumination: Illumination in which blue LED chips with a size of 1 mm square that emit light at a central wavelength of 453 nm are arranged in a line at intervals of 0.2 mm. The length of the line is 50 mm. The illuminance at a distance of 20 mm from the LED chip when no sample is placed is 200,000 Lx.
Glass plate: A glass plate having a rectangular parallelepiped shape with a main surface size of 50 mm square and a thickness of 1.8 mm, and having a main surface and end surfaces mirror-polished.
The glass plate according to any one of claims 1 to 9, wherein the content of CeO 2 is 200 ppm by mass or less on an oxide basis.
A light guide plate made of the glass plate according to any one of claims 1 to 10 and used for a quantum dot display using a blue LED.