JP2020030885A - Glass plate - Google Patents

Abstract

To improve brightness while facilitating handling, when it is used as, for example, a light guide plate of a planar light emitting device.SOLUTION: A glass plate 12 includes a first face (26) that is a surface, a second face (32) constituting a back face against the surface, a light receiving face 28 provided almost vertically to the first face and the second face between the first face and the second face, and receiving light radiated from a light source, and inclined faces 40 and 42 respectively provided between the light reception face 28 and the first face (26) and between the light reception face 28 and the second face (32). Thickness from the first face to the second face is 1.4 mm or more and 2.2 mm or less, and respective inclination angles of the inclined faces 40 and 42 to the first face and the second face are 0.5 degrees or more and 5.0 degrees or less.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a glass plate.

  2. Description of the Related Art A liquid crystal display device represented by a liquid crystal television, a digital signage, or the like includes a planar light emitting device constituting a backlight, and a liquid crystal panel arranged to face a light emitting surface of the planar light emitting device. The planar light emitting device includes a direct type and an edge light type, and an edge light type capable of reducing the size of a light source is often used. The edge light type planar light emitting device has a light source, a light guide plate, a reflection sheet, various optical sheets (a diffusion sheet, a brightness enhancement sheet, and the like), and the like. Patent Documents 1 and 2 disclose that a glass plate having high internal transmittance, high rigidity, and excellent heat resistance is used as a light guide plate of a planar light emitting device.

  The glass plate has higher rigidity than the acrylic plate used as the light guide plate, and has excellent heat resistance. However, if the glass plate is kept cut, there is a problem that the edges are sharp and handling is difficult. Patent Document 3 discloses a configuration in which a chamfered surface inclined with respect to a main plane and an end surface of a glass plate is provided at an edge of the glass plate. As disclosed in Patent Document 3, the shape of the chamfered surface is generally a shape in which the inclination angle with respect to the main plane and the end surface is 45 degrees in a cross section perpendicular to the main plane and the end surface of the glass plate. .

JP 2013-093195 A JP 2013-030279 A WO 2013/031548 (WO2013 / 031548) JP 2014-103049 A

  However, if a chamfered surface as described in Patent Document 3 is provided, light incident on the inside of the glass plate from the chamfered surface is largely bent by refraction. And there is a problem that light leaks outside.

  Patent Document 4 describes a configuration in which an inclined portion is provided in a light guide plate formed of a transparent plastic plate made of an acrylic resin or the like in order to improve non-uniformity of luminance distribution of light emitted from the light guide plate. Have been.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a glass plate capable of improving brightness while facilitating handling when used as a light guide plate of a planar light emitting device, for example.

According to one aspect of the invention,
A first surface that is a surface;
A second surface constituting a back surface with respect to the surface,
A light receiving surface that is provided substantially perpendicular to the first surface and the second surface between the first surface and the second surface, and that receives light emitted from a light source;
Inclined surfaces provided between the light receiving surface and the first surface, and between the light receiving surface and the second surface,
Including
A thickness from the first surface to the second surface is 1.4 mm or more and 2.2 mm or less,
A glass plate is provided, in which an inclination angle of the inclined surface with respect to each of the first surface and the second surface is 0.5 degrees or more and 5.0 degrees or less.

Also, according to an aspect of the present invention,
A first surface that is a surface;
A second surface constituting a back surface with respect to the surface,
A light receiving surface that is provided substantially perpendicular to the first surface and the second surface between the first surface and the second surface, and that receives light emitted from a light source;
Inclined surfaces provided between the light receiving surface and the first surface, and between the light receiving surface and the second surface,
Including
A thickness from the first surface to the second surface is 1.4 mm or more and 2.2 mm or less,
In a cross section perpendicular to the first surface and the light receiving surface, a length a of each of the inclined surfaces in an extending direction of the first surface and a length of each of the inclined surfaces in an extending direction of the light receiving surface A glass plate is provided wherein b is a / b = 11.43 or more and 114.59 or less.

  According to the glass plate of the present invention, for example, when used as a light guide plate of a planar light emitting device, it is possible to improve the luminance while facilitating handling.

It is a side view showing an example of the composition of the liquid crystal display in this embodiment. It is a perspective view showing an example of composition of a glass plate in this embodiment. It is an expanded sectional view showing an example of composition of a glass plate in this embodiment. It is a figure showing a simulation result of an example.

  Next, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same or corresponding members or components are denoted by the same or corresponding reference numerals, and redundant description is omitted. Further, the drawings are not intended to show relative ratios between members or components unless otherwise specified. Thus, specific dimensions can be determined by one skilled in the art in light of the following non-limiting embodiments.

[Liquid crystal display device 10]
FIG. 1 is a side view illustrating an example of the configuration of the liquid crystal display device 10 according to the present embodiment.

  The liquid crystal display device 10 includes a planar light emitting device 14 and a liquid crystal panel 16. The liquid crystal display device 10 is mounted on a thin electronic device such as a liquid crystal television and a digital signage. The planar light emitting device 14 includes the glass plate 12. In the present embodiment, the glass plate 12 can be used as a glass light guide plate.

<Liquid crystal panel 16>
The liquid crystal panel 16 is configured by stacking an alignment layer, a transparent electrode, a glass substrate, and a polarizing filter so as to sandwich a liquid crystal layer disposed at the center in the thickness direction. A color filter is provided on one side of the liquid crystal layer. The molecules of the liquid crystal layer rotate around the light distribution axis by applying a driving voltage to the transparent electrode, thereby performing a predetermined display.

<Surface emitting device 14>
The planar light emitting device 14 of the present embodiment can be of an edge light type. Thereby, the thickness can be reduced. The planar light emitting device 14 includes a light source 18, a glass plate 12, a reflection sheet 20, a transparent resin layer 21, various optical sheets 22, and reflection dots 24. The transparent resin layer 21 may be formed not only on one side but also on both sides, and the transparent resin layer 21 may be bonded to a part of the reflection sheet 20 or various optical sheets 22.

<Light source 18>
The light source 18 is not particularly limited, but an LED (Light Emitting Diode), a hot cathode tube, or a cold cathode tube can be used. The light source 18 is arranged at a position facing the light receiving surface 28 of the glass plate 12. In addition, by providing the reflector 30 on the back side of the light source 18, the efficiency of incidence of light emitted radially from the light source 18 on the glass plate 12 is increased.

<Glass plate 12>
The glass plate 12 will be described with reference to FIG. FIG. 2 is a perspective view illustrating an example of the configuration of the glass plate 12 in the present embodiment.

  The glass plate 12 includes a light exit surface 26 (first surface) that is a front surface, a light reflection surface 32 (second surface) that constitutes a back surface with respect to the front surface, and a light exit surface 26 and a light reflection surface 32. The light receiving surface 28 is provided substantially perpendicular to the light exit surface 26 and the light reflection surface 32, and receives light emitted from the light source 18, the end surfaces 34, 36, and 38, and the inclined surfaces 40 and 42.

  The light emitting surface 26 is a surface facing the liquid crystal panel 16. In the present embodiment, the light exit surface 26 is rectangular in plan view, but the shape of the light exit surface 26 is not limited to this. Further, the size of the light exit surface 26 is determined in accordance with the liquid crystal panel 16 and is not particularly limited. Since the glass plate 12 has high rigidity, the larger the size, the more the effect is exhibited.

  The light reflecting surface 32 is a surface on the opposite side of the light emitting surface 26. The light reflecting surface 32 is configured to be substantially parallel to the light emitting surface 26. Further, the shape and size of the light reflecting surface 32 are configured to be the same as those of the light emitting surface 26.

  However, the light reflecting surface 32 does not necessarily have to be parallel to the light emitting surface 26, and may be configured to have a step or an inclination. Further, the size of the light reflecting surface 32 may be different from the size of the light emitting surface 26.

  The light receiving surface 28 is a light incident end surface of the glass plate 12 facing the light source 18. The end faces 34, 36 and 38 are non-light incident end faces of the glass plate 12 excluding the light receiving surface 28. The end surface 38 is a surface opposite to the light receiving surface 28. The end surfaces 34 and 36 face each other and are provided between the light emitting surface 26 and the light reflecting surface 32, respectively.

  The light receiving surface 28 is mirror-finished at the time of manufacturing the glass that is the glass plate 12. The surface roughness Ra of the light receiving surface 28 is 0.1 μm or less, preferably less than 0.03 μm, and more preferably 0.1 μm so that the light from the light source 18 can effectively enter the inside of the glass plate 12. 001 μm or less, particularly preferably 0.0005 μm or less. Thereby, the light entering efficiency of the light entering the inside of the glass plate 12 from the light source 18 is enhanced.

  Since the light from the light source 18 does not enter the end surfaces 34, 36, and 38 of the glass plate 12, it is not necessary to process the surface as precisely as the light receiving surface 28, and the surface roughness Ra is 0.8 μm. The following may be sufficient. However, the surface roughness Ra of the end faces 34, 36, and 38 is preferably 0.4 μm or less, more preferably 0.1 μm or less, in order to suppress the occurrence of luminance unevenness due to light scattering at the end faces. is there. However, the surface roughness Ra of the end surfaces 34, 36, and 38 may be equal to the surface roughness Ra of the light receiving surface 28 from the viewpoint of improving production efficiency. In addition, in this specification, when it describes as surface roughness Ra, it shall mean the arithmetic average roughness (center line average roughness) by JISB0601-JISB0031.

  The inclined surface 40 and the inclined surface 42 are provided between the light receiving surface 28 and the light emitting surface 26 and between the light receiving surface 28 and the light reflecting surface 32, respectively. That is, the inclined surface 40 is provided between the light receiving surface 28 and the light emitting surface 26 and adjacent to the light receiving surface 28 and the light emitting surface 26. Similarly, an inclined surface 42 is provided between the light reflecting surface 32 and the light receiving surface 28 and adjacent to the light receiving surface 28 and the light reflecting surface 32. By providing such an inclined surface 40 and an inclined surface 42, handling of the glass plate 12 can be facilitated.

  The configuration of the inclined surfaces 40 and 42 in the present embodiment will be described with reference to FIG. FIG. 3 is an enlarged cross-sectional view illustrating an example of the configuration of the glass plate 12 in the present embodiment. The inventor of the present application has diligently studied the shapes of the inclined surfaces 40 and 42 that make it possible to effectively use the light amount of the light source 18 and to easily handle the glass plate 12 as the glass plate 12.

  In the present embodiment, the inclination angle θ1 of the inclined surface 40 with respect to the light exit surface 26 and the inclination angle θ2 of the inclined surface 42 with respect to the light reflecting surface 32 can be 5.0 degrees (°) or less. As a result, as described later, the luminance can be improved as compared with the conventional configuration in which the chamfered surface is provided on the light receiving surface of the glass plate. Further, each of the inclination angle θ1 and the inclination angle θ2 can be 0.5 degrees (°) or more. Thereby, the luminance can be improved. Further, by setting the inclination angles of the inclined surfaces 40 and 42 to about 0.5 degrees or more, the handling of the glass plate 12 can be facilitated.

  Further, in the present embodiment, in a section perpendicular to the light emitting surface 26 and the light receiving surface 28, the length a of each of the inclined surfaces 40 and 42 in the extension direction of the light emitting surface 26 and the extension of the light receiving surface 28 The length b of each of the inclined surface 40 and the inclined surface 42 in the direction can be set to a / b = 11.43 or more (corresponding to the inclination angle θ1 (or θ2) = 5 degrees or less). Thereby, the brightness can be improved as compared with the conventional configuration in which the chamfered surface is provided on the light receiving surface of the glass plate. A / b = 114.59 or less (corresponding to the inclination angle θ1 (or θ2) = 0.5 ° or more). Thereby, the brightness can be improved and the handling of the glass plate 12 can be facilitated.

  In the present embodiment, the length a of each of the inclined surface 40 and the inclined surface 42 in the extension direction of the light emitting surface 26 is preferably 1.5 mm or more, more preferably 2.0 mm or more and 4.5 mm or less. . If the value of the length a is too large, the light receiving surface becomes small and care must be taken in handling. Therefore, by setting the value of the length a within a certain range, the handling of the glass plate can be facilitated.

  In other words, a first intersection P1 at which the light emitting surface 26 and the inclined surface 40 or the light reflecting surface 32 and the inclined surface 42 intersect, a second intersection P2 at which the light receiving surface 28 intersects the inclined surface 40 or 42, Assuming that a point at which the first extension line L1 extending along the light exit surface 26 or the light reflection surface 32 intersects with the second extension line L2 extending along the light receiving surface 28 is a third intersection point P3, the length is a is the distance from the first intersection P1 to the third intersection P3, and the length b is the distance from the second intersection P2 to the third intersection P3. However, when the distance between the intersections is difficult to measure, the intersection of the extension line extended along the slope 40 or the slope 42 and the second extension line L2 is P2, and the first extension line L1 and the slope 40 Alternatively, the length a and the length b are calculated with the intersection of the extension lines extended along 42 as P1.

  The surface roughness Ra of the inclined surfaces 40 and 42 is preferably 0.8 μm or less, more preferably 0.3 μm or less, and more preferably 0.1 μm or less. By setting the surface roughness Ra of the inclined surface 40 and the inclined surface 42 to 0.8 μm or less, it is possible to suppress the occurrence of luminance unevenness of light emitted from the glass plate 12. In other words, the incident light can be efficiently taken into the glass plate 12 by setting the surface roughness Ra of the inclined surface 40 and the inclined surface 42 to 0.8 μm or less. Further, by setting the surface roughness Ra of the inclined surfaces 40 and 42 to 0.3 μm or less, the amount of cullet generation can be suppressed. On the other hand, the lower limit of the surface roughness Ra of the inclined surface 40 and the inclined surface 42 is not limited, and the smaller the Ra, the more the occurrence of luminance unevenness of the glass plate 12 can be suppressed. It costs. From the viewpoint of improving the production efficiency, the surface roughness Ra of the inclined surface 40 and the inclined surface 42 may be larger than the surface roughness Ra of the light receiving surface 28.

  The thickness (the thickness from the light exit surface 26 to the light reflection surface 32) of the glass plate 12 according to the present embodiment can be set to 1.4 mm or more and 2.2 mm or less. By setting the thickness of the glass plate 12 to 2.2 mm or less, the planar light emitting device 14 can be made thin. Further, by setting the thickness of the glass plate 12 to 1.4 mm or more, sufficient rigidity can be obtained. The thickness of the glass plate 12 is not limited to this value, but even with this thickness, compared to a planar light emitting device having an acrylic light guide plate with a thickness of 4 mm or more, The planar light emitting device 14 having sufficient strength can be provided. The physical properties of the glass plate 12 will be described later.

<Reflective sheet 20>
Returning to FIG. 1, the reflection sheet 20 is formed by coating a light reflection member on the surface of a resin sheet such as an acrylic resin. The reflection sheet 20 is provided so as to face the light reflection surface 32 of the glass plate 12. In addition, the reflection sheet 20 may be provided on the end faces 34, 36 and 38. Each of the reflection sheets 20 may be disposed with a space from the glass plate 12 or may be bonded to the glass plate 12 with an adhesive transparent resin layer.

  When the reflection sheet 20 is provided on the end surfaces 34, 36, and 38, the reflection sheet 20 may be provided on at least the end surface 38 facing the light receiving surface 28 among the end surfaces 34, 36, and 38. Thus, the light incident from the light receiving surface 28 travels in a direction away from the light source 18 (to the right in FIG. 1) while being repeatedly totally reflected inside the glass plate 12, and reaches the end surface 38. The light is again reflected inside the glass plate 12 by the reflection sheet 20. When the reflection sheet 20 is also provided on the end surfaces 34 and 36, the light scattered inside the glass plate 12 is transmitted to the inside of the glass plate 12 by the reflection sheet 20 when reaching the end surfaces 34 and 36. It can be reflected again. Thereby, the light amount of the light source 18 can be effectively used.

  As a material of the resin sheet constituting the reflection sheet 20, an acrylic resin is exemplified, but not limited thereto. For example, a polyester resin such as a PET resin, a urethane resin, and a material obtained by combining them can be used. . As the light reflecting member constituting the reflecting sheet 20, for example, a film in which bubbles or particles are included in a resin, a metal deposition film, or the like can be used.

  The reflective sheet 20 may be provided with an adhesive transparent resin layer, and may be bonded to the glass plate 12. As the adhesive transparent resin layer provided on the reflection sheet 20, for example, an acrylic resin, a silicone resin, a urethane resin, a synthetic rubber, or the like can be used. Although the thickness of the reflection sheet 20 is not particularly limited, a thickness of, for example, 0.01 to 0.50 mm can be used.

<Transparent resin layer 21>
The transparent resin layer 21 may be a hard coat layer, an antireflection film (AR coat), an adhesive layer, a lenticular layer, or an antistatic film (antistatic coat) for protecting the surface of the glass plate 12 from scratches. it can. The transparent resin layer 21 is applied by a coating method such as spray coating, or is applied by a squeegee method, or a mold is pressed by an imprint method, or after being printed by a printing method such as gravure printing, is irradiated with ultraviolet light, or It may be formed by heating.

<Various optical sheets 22>
The various optical sheets 22 can be a diffusion sheet, a brightness enhancement sheet, a lenticular sheet, or the like. As the various optical sheets 22, a milky white acrylic resin film or the like can be used. Since the various optical sheets 22 diffuse the light emitted from the light emitting surface 26 of the glass plate 12, the back side of the liquid crystal panel 16 is irradiated with uniform light without luminance unevenness. In addition, the various optical sheets 22 may be disposed facing a predetermined position so as not to abut on the glass plate 12, or may be bonded to the glass plate 12 via the transparent resin layer 21.

<Reflection dot 24>
The light reflection surface 32 is provided with a plurality of circular reflection dots 24. In FIG. 1, the reflection dots 24 are collectively described. However, the plurality of reflection dots may be arranged in a grid pattern, may be arranged in any other pattern, or may be arranged randomly. However, it is appropriately adjusted so that the luminance distribution of the light emitted from the light exit surface 26 becomes uniform. The reflection dot 24 is formed by printing a resin into a dot shape by a method such as printing, and may contain scattering particles or bubbles.

  Note that the brightness of the light incident from the light receiving surface 28 gradually decreases as it travels while being repeatedly reflected inside the glass plate 12. Therefore, in the present embodiment, the size of the reflection dots 24 may be different from the light receiving surface 28 toward the end surface 38. Specifically, the diameter of the reflection dot 24 in a region near the light receiving surface 28 can be set to be small, and the diameter of the reflection dot 24 can be set to become larger as it goes toward the light traveling direction. The diameter of the reflection dot 24 is appropriately adjusted so that the luminance distribution of the light emitted from the light emission surface 26 becomes uniform.

  As described above, by changing the size of the reflection dots 24 in the traveling direction of the light inside the glass plate 12, the luminance of the light emitted from the light exit surface 26 can be made uniform, and the occurrence of luminance unevenness can be reduced. Can be suppressed. Note that the same effect can be obtained by changing the number density of the reflection dots 24 in the traveling direction of light inside the glass plate 12 instead of changing the size of the reflection dots 24. The same effect can be obtained by forming a groove on the light reflecting surface 32 instead of the reflective dot 24 so as to reflect the incident light.

  In the planar light emitting device 14 configured as described above, the light that has entered the inside of the glass plate 12 from the light source 18 repeatedly repeats on the inner surface of the light emitting surface 26 and the inner surface of the light reflecting surface 32 of the glass plate 12. It progresses while being reflected. Light whose traveling direction has been changed by the reflection dots 24 and the reflection sheet 20 is emitted to the outside from a light emission surface 26 of the glass plate 12 facing the liquid crystal panel 16. The light emitted to the outside is incident on the liquid crystal panel 16 after being diffused by the various optical sheets 22.

<Physical properties of glass plate 12>
Next, the physical properties of the glass plate 12 will be described. The glass plate 12 is made of highly transparent glass. In the embodiment, a multi-component oxide glass is used as a glass material used for the glass plate 12.

  Specifically, it is preferable to use, as the glass plate 12, glass having a length of 50 mm and an average internal transmittance of 90% or more at a wavelength of 400 to 700 nm. Thereby, attenuation of the light incident on the glass plate 12 can be suppressed as much as possible. The transmittance at a length of 50 mm is obtained by cutting the glass plate 12 in a direction perpendicular to the main plane, so that the first and second glass plates are sampled from the central portion of the glass plate in a size of 50 mm × 50 mm and opposed to each other. In the sample A in which the second fractured surface has an arithmetic average roughness Ra ≦ 0.03 μm, a spectrometer capable of measuring at a length of 50 mm in the normal direction from the first fractured surface and at a length of 50 mm. The measurement is performed with a measuring device (for example, UH4150: manufactured by Hitachi High-Technologies Corporation) after making the beam width of the incident light narrower than the plate thickness with a slit or the like. By removing the loss due to reflection on the surface from the thus obtained transmittance at a length of 50 mm, an internal transmittance at a length of 50 mm can be obtained. The average internal transmittance at a wavelength of 400 to 700 nm at a length of 50 mm is preferably 92% or more, more preferably 95% or more, further preferably 98% or more, and particularly preferably 99% or more.

  The total amount A of the iron content of the glass used as the glass plate 12 is preferably 100 mass ppm or less, in order to satisfy the above-described average internal transmittance at a wavelength of 400 to 700 nm at a length of 50 mm, and 40 mass ppm. Or less, more preferably 20 mass ppm or less. On the other hand, the total amount A of the iron content of the glass used as the glass plate 12 is preferably not less than 5 ppm by mass, when producing a multi-component oxide glass, from the viewpoint of improving the melting property of the glass, It is more preferably at least 8 ppm by mass, further preferably at least 10 ppm by mass. In addition, the total amount A of the iron content of the glass used as the glass plate 12 can be adjusted by the amount of iron added at the time of glass production.

In this specification, the total amount A of the iron content of the glass is represented as the content of Fe ₂ O ₃ , but all the iron present in the glass exists as Fe ³⁺ (trivalent iron). Not necessarily. Usually, Fe ³⁺ and Fe ²⁺ (divalent iron) are simultaneously present in the glass. Fe ²⁺ and Fe ³⁺ have absorption in the wavelength range of 400 to 700 nm, but the absorption coefficient of Fe ²⁺ (11 cm ⁻¹ Mol ⁻¹ ) is higher than that of Fe ³⁺ (0.96 cm ⁻¹ Mol ⁻¹ ). Is also one order of magnitude larger, so that the internal transmittance at a wavelength of 400 to 700 nm is further reduced. Therefore, it is preferable that the content of Fe ²⁺ be small in order to increase the internal transmittance at a wavelength of 400 to 700 nm.

The content B of Fe ²⁺ of the glass used as the glass plate 12 is preferably 20 mass ppm or less, in order to satisfy the above-mentioned average internal transmittance in the visible light region with an effective optical path length, and is preferably 10 mass ppm or less. More preferably, it is still more preferably 5 ppm by mass or less. On the other hand, the content B of Fe ²⁺ of the glass used as the glass plate 12 is preferably 0.01 mass ppm or more, when producing a multi-component oxide glass, from the viewpoint of improving the melting property of the glass. , 0.05 mass ppm or more, and even more preferably 0.1 mass ppm or more.

The content of Fe ²⁺ in the glass used as the glass plate 12 can be adjusted by the amount of the oxidizing agent added during the production of the glass, the melting temperature, or the like. The specific types of oxidizing agents added during the production of glass and the amounts thereof will be described later. The content A of Fe ₂ O ₃ was determined by fluorescent X-ray measurement, a content of total iron as calculated as _Fe 2 _{O 3} (mass ppm). The content B of Fe ²⁺ was measured according to ASTM C169-92. The measured content of Fe ²⁺ was expressed in terms of Fe ₂ O ₃ .

  Specific examples of the composition of the glass used as the glass plate 12 are shown below. However, the composition of the glass used as the glass plate 12 is not limited to these.

One structural example of a glass used as the glass plate 12 (Configuration Example A) is a mass percentage based on oxides, SiO ₂ 60-80%, the _Al 2 _{O 3 0~7%,} the MgO 0 %, 0-20% of CaO, the SrO 0 to 15%, 0 to 15% of BaO, 3 to 20% of Na ₂ O, 0% to _{K 2 O, Fe 2} O ₃ 5 to 100 mass ppm.

Another configuration example (configuration example B) of the glass used as the glass plate 12 is as follows: 45 to 80% of SiO ₂ , more than 7% of Al ₂ O _3, and 30% or less in terms of mass percentage on an oxide basis. 0 to 15% ₂ O ₃ , 0 to 15% MgO, 0 to 6% CaO, 0 to 5% SrO, 0 to 5% BaO, 7 to 20% Na ₂ O, K ₂ O 0-10%, a ZrO ₂ 0 to 10%, including _Fe 2 _{O 3} 5 to 100 mass ppm.

Yet another configuration example of the glass used as the glass plate 12 (configuration example C) is a mass percentage based on oxides, SiO ₂ 45 to 70%, the _{Al 2 O 3 10~30%, B} 2 O _{3 is 0} to 15%, MgO, CaO, SrO and BaO are 5 to 30% in total, Li ₂ O, Na ₂ O and K ₂ O are 0% or more and less than 3% in total, and Fe ₂ O ₃ is Contains 5 to 100 mass ppm.

  However, the glass used as the glass plate 12 is not limited to these.

  The composition range of each component of the glass composition of the glass plate 12 of the present embodiment having the above-described components will be described below. In addition, the unit of the content of each composition is expressed as a percentage by mass or as ppm by mass on an oxide basis, and is simply expressed as “%” or “ppm”, respectively.

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 Configuration Example A, and preferably 45% or more in Configuration Example B. The above is more preferably 50% or more, and in Configuration Example C, it is preferably 45% or more, and more preferably 50% or more.

On the other hand, the content of SiO ₂ is intended to facilitate melting and improve the foam quality, and to keep the content of divalent iron (Fe ²⁺ ) in the glass low to improve the optical characteristics. Therefore, in Configuration Example A, it is preferably 80% or less, more preferably 75% or less, in Configuration Example B, preferably 80% or less, more preferably 70% or less, and in Configuration Example C, , Preferably 70% or less, more preferably 65% or less.

Al ₂ O ₃ is an essential component for improving the weather resistance of the glass in Configuration Examples B and C. In order to maintain the weather resistance required for practical use in the glass of this embodiment, the content of Al ₂ O ₃ is preferably 1% or more, more preferably 2% or more in Configuration Example A. In Example B, it is preferably more than 7%, more preferably 10% or more, and in Configuration Example 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, to improve the optical characteristics, and to improve the foam quality, the content of Al ₂ O ₃ is preferable in the configuration example A. Is 7% or less, more preferably 5% or less, in Configuration Example B, preferably 30% or less, more preferably 23% or less, and in Configuration Example 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, it does not cause inconvenience such as generation of striae (ream) due to volatilization and erosion of the furnace wall. , B ₂ O ₃ is preferably 5% or less, more preferably 3% or less in the glass A, and is preferably 15% or less, more preferably 12% in the configuration examples B and C. It is as follows.

Alkali metal oxides such as Li ₂ O, Na ₂ O, and K ₂ O are useful components for promoting melting of glass raw materials and adjusting thermal expansion, viscosity, and the like.

Therefore, the content of Na ₂ O in Configuration Example A is preferably 3% or more, and more preferably 8% or more. In the configuration example B, the content of Na ₂ O is preferably at least 7%, more preferably at least 10%. However, in order to maintain the clarity at the time of melting and to maintain the bubble quality of the produced glass, the content of Na ₂ O is preferably 20% or less in Configuration Examples A and B, and 15% or less. The content is further preferably set to the following, and in Configuration Example C, the content is preferably set to 3% or less, more preferably 1% or less.

Further, the content of K ₂ O is preferably 10% or less, more preferably 7% or less in Configuration Examples A and B, and is preferably 2% or less, more preferably, in Configuration Example C. 1% or less.

Li ₂ O is an optional component. In order to facilitate vitrification, to reduce the iron content contained as an impurity derived from the raw material, and to reduce the batch cost, in the configuration examples A, B, and C, , Li ₂ O in an amount of 2% or less.

In addition, the total content of these alkali metal oxides (Li ₂ O + Na ₂ O + K ₂ O) is as follows in constitutional examples A and B in order to maintain clarity at the time of melting and maintain foam quality of the produced glass. , Preferably 5% to 20%, more preferably 8% to 15%, and in Configuration Example C, preferably 0% to 2%, more preferably 0% to 1%.

  Alkaline earth metal oxides such as MgO, CaO, SrO, and BaO are components useful for promoting 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 melting. Further, since it has the effect of reducing the specific gravity and making the glass plate less likely to have flaws, it can be contained in Configuration Examples A, B and C. In order to lower the coefficient of thermal expansion of the glass and improve the devitrification characteristics, the content of MgO is preferably 10% or less, more preferably 8% or less in Configuration Example A. In Example B, it is preferably 15% or less, more preferably 12% or less, and in Configuration Example C, it is preferably 10% or less, more preferably 5% or less.

  CaO is a component that promotes the melting of the glass raw material and adjusts the viscosity, thermal expansion, and the like, and therefore can be contained in the structural examples A, B, and C. In order to obtain the above effects, in the configuration example A, the content of CaO is preferably 3% or more, more preferably 5% or more. Further, in order to make the devitrification good, in Configuration Example A, it is preferably 20% or less, more preferably 10% or less, and in Configuration Example B, preferably 6% or less, and more preferably. 4% or less.

  SrO has the effect of increasing the coefficient of thermal expansion and lowering the high temperature viscosity of glass. In order to obtain such an effect, SrO can be contained in the structural examples A, B and C. However, in order to suppress the thermal expansion coefficient of the glass, the content of SrO is preferably 15% or less, more preferably 10% or less in Configuration Examples A and C. , Preferably 5% or less, more preferably 3% or less.

  BaO, like SrO, has the effect of increasing the coefficient of thermal expansion and lowering the high-temperature viscosity of glass. BaO can be contained in order to obtain the above effects. However, in order to suppress the coefficient of thermal expansion of the glass to be low, it is preferably 15% or less, more preferably 10% or less, in Structure Examples A and C, and 5% or less in Structure Example B. Is preferably set to 3% or less.

  In addition, the total content of these alkaline earth metal oxides (MgO + CaO + SrO + BaO) is preferably 10 in configuration example A in order to keep the coefficient of thermal expansion low, improve the devitrification characteristics, and maintain the strength. % To 30%, more preferably 13% to 27%, in Configuration Example B, preferably 1% to 15%, more preferably 3% to 10%, and in Configuration Example C, preferably 5% to 5%. % To 30%, more preferably 10% to 20%.

In the glass composition of the glass of the glass plate 12 of the present embodiment, in order to improve the heat resistance and surface hardness of the glass, ZrO ₂ is used as an optional component in the composition examples A, B, and C, and is 10% or less, and preferably 10% or less. You may make it contain 5% or less. When the content is 10% or less, the glass is less likely to be devitrified.

In the glass composition of the glass of the glass plate 12 of the present embodiment, 5 to 100 ppm of Fe ₂ O ₃ may be contained in the structural examples A, B and C in order to improve the meltability of the glass. The preferable range of the amount of Fe ₂ O ₃ is as described above.

Further, the glass of the glass plate 12 of the present embodiment 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. It is more preferably at most 0.4%, further preferably at most 0.3%, further preferably at most 0.25%.

Further, the glass of the glass plate 12 of the present embodiment may contain one or more of Sb ₂ O ₃ , SnO ₂ and As ₂ O ₃ as an oxidizing agent and a fining agent. In this case, the content of Sb ₂ O ₃ , SnO ₂ or As ₂ O ₃ is preferably from 0 to 0.5% in terms of mass percentage. The content is more preferably 0.2% or less, still more preferably 0.1% or less, and further preferably substantially no content.

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

  Further, the glass of the glass plate 12 of the present embodiment may contain NiO. When NiO is contained, NiO also functions as a coloring component. Therefore, the content of NiO is preferably set to 10 ppm or less with respect to the total amount of the above glass composition. In particular, NiO is preferably at most 1.0 ppm, more preferably at most 0.5 ppm, from the viewpoint of not lowering the internal transmittance of the glass plate at a wavelength of 400 to 700 nm.

The glass of the glass plate 12 of the present embodiment may contain Cr ₂ O ₃ . When Cr ₂ O ₃ is contained, since Cr ₂ O ₃ also functions as a coloring component, the content of Cr ₂ O ₃ is preferably set to 10 ppm or less with respect to the total amount of the above glass composition. In particular, Cr ₂ O ₃ is preferably at most 1.0 ppm, more preferably at most 0.5 ppm, from the viewpoint of not lowering the internal transmittance of the glass plate at a wavelength of 400 to 700 nm.

The glass of the glass plate 12 of the present embodiment may contain MnO ₂ . When MnO ₂ is contained, since MnO ₂ also functions as a component that absorbs visible light, the content of MnO ₂ is preferably set to 50 ppm or less based on the total amount of the above glass composition. In particular, MnO ₂ is preferably set to 10 ppm or less from the viewpoint of not lowering the internal transmittance of the glass plate at a wavelength of 400 to 700 nm.

The glass of the glass plate 12 of the present embodiment may include 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 based on the total amount of the above glass composition. The content of TiO ₂ is more preferably 500 ppm or less, and particularly preferably 100 ppm or less, from the viewpoint of not lowering the internal transmittance of the glass plate at a wavelength of 400 to 700 nm.

The glass of the glass plate 12 of the present embodiment may contain CeO ₂ . CeO ₂ has the effect of lowering the redox of iron, and can reduce the ratio of the amount of Fe ^{2+ to the} total amount of iron. On the other hand, the content of CeO ₂ is preferably 1000 ppm or less based on the total amount of the above-mentioned glass composition in order to suppress the iron redox from dropping to less than 3%. Further, the content of CeO ₂ 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.

The glass of the glass plate 12 of the present embodiment may include at least one component selected from the group consisting of CoO, V ₂ O ₅ and CuO. When these components are contained, they also function as components that absorb visible light, so that the content of the components is preferably 10 ppm or less with respect to the total amount of the above glass composition. In particular, it is preferable that these components are not substantially contained so as not to lower the internal transmittance of the glass plate at a wavelength of 400 to 700 nm.

[Method of manufacturing glass plate 12]
Next, a method for manufacturing the glass plate 12 will be described. The glass plate 12 can have a desired size by cutting a glass material having a thickness corresponding to the glass plate thickness of the glass plate 12 (T in FIG. 3), for example. As a method of cutting the glass material, for example, a scribe cutting method, a laser cutting method, or the like can be performed.

  Thereafter, mirror processing is performed on the light receiving surface 28. Thereby, the light receiving surface 28 having a surface roughness Ra of 0.1 μm or less can be formed.

  Subsequently, a grinding process or a polishing process is performed between the light receiving surface 28 and the light emitting surface 26 and between the light receiving surface 28 and the light reflecting surface 32. Thereby, the inclined surface 40 and the inclined surface 42 are formed. The polishing process for forming the inclined surface 40 and the inclined surface 42 may be performed before the mirror finishing of the light receiving surface 28, or may be performed simultaneously with the mirror finishing of the light receiving surface 28.

  When forming the inclined surface 40 and the inclined surface 42, a grindstone may be used as a tool for performing a grinding process or a polishing process, and in addition to the grindstone, a buff or a brush made of cloth, leather, rubber, or the like is used. In this case, an abrasive such as cerium oxide, alumina, carborundum, or colloidal silica may be used. Above all, it is preferable to use a grindstone as the polishing tool from the viewpoint of dimensional stability.

  Through the above processing, the glass plate 12 is manufactured. The transparent resin layer 21 can be formed on the light emitting surface 26 or the light reflecting surface 32 by a coating method, a printing method, or the like after the glass plate 12 is manufactured. The transparent resin layer 21 can be formed on the substrate 22 and then bonded to the glass plate 12 later. The reflection dots 24 can be formed on the light reflection surface 32 by a printing method or the like after the glass plate 12 is manufactured.

  Note that, in the glass plate 12, edges between the surfaces, for example, between the light emitting surface 26 and each of the end surfaces 34, 36, and 38, and between the light reflecting surface 32 and each of the end surfaces 34, 36, and 38, and further, the end surface 34, The edge of the glass plate 12 between each of 36 and 38 may be appropriately chamfered.

〔Example〕
In order to find the above range, the inventor of the present application performed a simulation using 10 million light beams using light tracing software (Light Tools: manufactured by Cybernet System). In the model used in this simulation, the light source 18 is arranged at a distance of 0.2 mm from the light receiving surface 28 so as to face the rectangular glass plate 12 having a size of 100 mm × 620 mm, and the reflector is surrounded by the light source 18. 30 were placed. The light source 18 includes a plurality of point light sources arranged in parallel, emits light in a wavelength range of 400 nm to 700 nm, and has a Lambertian light distribution characteristic.

  In this embodiment, the glass plate 12 has an inclined surface 40 and an inclined surface 42, and the inclination angle θ is between 0 ° and 8.1 ° (0 °, 0.8 °, 1.6 °, 2 °). The simulation was carried out with various changes at 0.5 °, 3.3 °, 4.1 °, 4.9 °, 5.7 °, 6.5 °, 7.3 °, 8.1 °). In each case, the inclination angles θ of the inclined surfaces 40 and 42 were equal. In each case, the length of the inclined surface 40 and the inclined surface 42 (FIG. 3A) was 3.5 mm. As the glass plate 12, those having a glass plate thickness (T in FIG. 3) of 2.1 mm, 1.8 mm and 1.5 mm were used.

  The height of the light source 18 was changed according to the thickness of the glass plate 12. The light source height was 1.6 mm when the glass plate thickness was 2.1 mm, and 1.0 mm when the glass plate thickness was 1.8 mm and 1.5 mm. This is because the height of the light source 18 is generally selected as close as possible to the thickness of the glass plate when actually configuring the backlight unit. It was assumed that there was no scattering on the light receiving surface 28, the inclined surface 40, and the inclined surface 42.

  The reflector 30 has a Gaussian reflection characteristic of σ = 15 °, and the diffuse reflectance is 99%. The glass plate 12 has a light exit surface 26 and a light reflection surface 32, and the reflection dots 24 are formed on the light reflection surface 32. Further, the reflection sheet 20 was disposed at a distance of 0.1 mm from the light reflection surface 32 so as to face the glass plate 12. The reflection sheet has a Gaussian reflection characteristic of σ = 15 ° and a diffuse reflectance of 99%.

  Further, a transparent resin layer 21 having a thickness of 50 μm is provided on the light emitting surface 26 side of the glass plate 12 from the position at least 5 mm away from the light receiving surface 28 (length in the same direction as in FIG. 3A). That is, the transparent resin layer 21 is not provided on the inclined surfaces 40 and 42. The transparent resin layer 21 has a refractive index of 1.520 at all wavelengths. In order to more accurately estimate the amount of non-guided light and the amount of guided light, in this model, it was assumed that there was no absorption of glass and transparent resin. The refractive index of glass is 1.532 at a wavelength of 435.8 nm, 1.527 at a wavelength of 486.1 nm, 1.523 at a wavelength of 546.1 nm, 1.521 at a wavelength of 587.6 nm, and 1.519 at a wavelength of 656.3 nm. , And those obtained by interpolating these values with an appropriate Cell Meyer coefficient were used.

<simulation result>
As a base configuration of the simulation, instead of the inclined surface 40 and the inclined surface 42 of the embodiment, the inclination angle is 45 degrees and the width is 0.15 mm (the same as θ1 and θ2 in FIG. The one having a rough chamfered yarn chamfered portion with a corresponding inclination angle of 45 degrees and a = b = 0.15 mm) was used. The thickness of the glass plate was the same as that of the glass plate 12 of the corresponding embodiment, and the height of the light source 18 was the same as that of the corresponding embodiment. As a parameter of the chamfered portion of the base configuration, it is assumed that the Gaussian scattering distribution characteristic has σ = 6 °. Other configurations are the same as those of the embodiment.

  For each condition (glass plate thickness, tilt angle), the in-plane average luminance improvement for the corresponding condition of the base configuration was calculated. FIG. 4 shows the simulation results.

  As shown in FIG. 4, the in-plane average luminance is improved by 3% or more with respect to the base structure by setting the inclination angle θ1 and the inclination angle θ2 to 5.0 degrees or less at any glass plate thickness. Was completed. Further, by providing the inclined surface 40 and the inclined surface 42 on the glass plate 12 (by setting the inclination angle θ1 and the inclination angle θ2 to be larger than 0 degree), the edge of the light receiving surface 28 of the glass plate 12 is kept cut. As compared with the case (when the inclination angles θ1 and θ2 = 0 degrees), the in-plane average luminance was able to be improved. However, from the viewpoint of facilitating the handling of the glass plate 12, it is preferable that each of the inclination angles θ1 and θ2 be 0.5 degrees or more.

  In the above-described embodiment, the simulation is performed when the glass plate 12 has a glass plate thickness of 2.1 mm, 1.8 mm, and 1.5 mm, but the inclination angle θ1 and the inclination angle θ2 are set to 0.5. When the glass plate thickness is in the range of 1.4 mm to 2.2 mm, the same effect of improving the average in-plane luminance and the effect of facilitating the handling of the glass plate 12 can be achieved even when the glass plate thickness is in the range of 1.4 mm to 2.2 mm. Is considered to be obtained.

  As described above, according to the glass plate 12 of the present embodiment, for example, when used as the light guide plate of the planar light emitting device 14, the brightness can be improved while facilitating the handling.

  As described above, the preferred embodiments of the present invention have been described in detail, but the present invention is not limited to the specific embodiments described above, and various modifications may be made within the scope of the present invention described in the claims. It can be modified and changed.

  Reference Signs List 10 liquid crystal display device, 12 glass plate, 14 planar light emitting device, 16 liquid crystal panel, 18 light source, 20 reflection sheet, 21 transparent resin layer, 22 various optical sheets, 24 reflection dots, 26 ... light emitting surface, 28 ... light receiving surface, 30 ... reflector, 32 ... light reflecting surface, 34, 36 and 38 ... end surface, 40 and 42 ... inclined surface

Claims (6)

A first surface that is a surface;
A second surface constituting a back surface with respect to the surface,
A light receiving surface that is provided substantially perpendicular to the first surface and the second surface between the first surface and the second surface, and that receives light emitted from a light source;
Inclined surfaces provided between the light receiving surface and the first surface, and between the light receiving surface and the second surface,
Including
A thickness from the first surface to the second surface is 1.4 mm or more and 2.2 mm or less,
A glass plate, wherein an inclination angle of the inclined surface with respect to each of the first surface and the second surface is 0.5 degrees or more and 5.0 degrees or less. A first surface that is a surface;
A second surface constituting a back surface with respect to the surface,
A light receiving surface that is provided substantially perpendicular to the first surface and the second surface between the first surface and the second surface, and that receives light emitted from a light source;
Inclined surfaces provided between the light receiving surface and the first surface, and between the light receiving surface and the second surface,
Including
A thickness from the first surface to the second surface is 1.4 mm or more and 2.2 mm or less,
In a cross section perpendicular to the first surface and the light receiving surface, a length a of each of the inclined surfaces in an extending direction of the first surface and a length of each of the inclined surfaces in an extending direction of the light receiving surface b is a glass plate in which a / b = 11.43 or more and 114.59 or less. It is a glass plate according to claim 1 or 2,
A glass plate, wherein in a cross section perpendicular to the first surface and the light receiving surface, a length a of each of the inclined surfaces in an extension direction of the first surface is 1.5 mm or more. It is a glass plate according to any one of claims 1 to 3,
A glass plate wherein each of the inclined surfaces has a surface roughness of 0.3 μm or less. It is a glass plate according to any one of claims 1 to 4,
A glass plate further including a transparent resin layer provided on one of the first surface and the second surface.   The glass plate according to claim 1, wherein the glass plate is used as a glass light guide plate.

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