TW201712380A - Glass plate for light guide plate - Google Patents

Abstract

In this glass plate 1 for a light guide plate, an extremity edge portion 9, which follows an edge on the light inlet side where light from a light source 3 is introduced, has chamfered surfaces 13, 14 between an end surface 12 and main surfaces 7, 8. The external angle [theta]1 formed by the chamfered surfaces 13, 14 and the main surfaces 7, 8 is 45 DEG or less. In a direction along the main surfaces 7, 8, the length L1 of the chamfered surfaces 13, 14 is 5 [mu]m or greater. The surface roughness Ra of the end surface 12 is 0.5 [mu]m or less.

Description

Glass plate for light guide plate

The present invention relates to a glass plate used as a substrate of a light guide plate, and more particularly to an end edge portion for improving a side along a light incident side and/or an opposite side end of a side opposite to a light incident side. A glass plate for the light guide plate at the side.

As is conventionally known, a liquid crystal display used as a display device of a thin information device is provided with a backlight. As such a backlight, an edge-lit backlight is mainly used. The edge type backlight includes a light guide plate that introduces light from a light source (for example, an LED) from an edge portion along a side that enters the light side to emit light.

As a substrate of the conventional light guide plate, a resin plate is generally used. According to this aspect, the conventional light guide plate is provided with a diffusion plate or the like on the light-emitting side of the resin plate, and a reflector or the like is attached to the surface on the opposite side.

however. When a resin plate is used as the substrate of the light guide plate, various properties such as deformation due to heat of the light source, deterioration in dimensional stability, difficulty in thinning, or influence by moisture may occur due to characteristics of the resin.

Therefore, in Patent Document 1, it is disclosed that a glass plate is used as a substrate of a light guide plate instead of a resin plate. Specifically, in this document, a light guide plate is disclosed in which a diffusion plate (diffusion film) is attached to one main surface of the glass plate, and a reflection plate (reflection film) is attached to the other main surface.

As described above, when a glass plate is used as the substrate of the light guide plate, various problems in the above-described use of the resin plate can be expected.

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2015-72896

However, when a glass plate is used as the substrate of the light guide plate, a new problem due to the characteristics of the glass plate is caused, that is, a new problem such as chipping or breakage is likely to occur. In addition, in an attempt to avoid such a problem, it must be considered whether the glass plate can satisfy the optical characteristics necessary for the light guide plate.

In view of the above, it is an object of the present invention to provide a glass substrate for a light guide plate which is less likely to be nicked or damaged, and which can easily satisfy the optical characteristics necessary for the light guide plate.

The present invention has been completed to solve the above problems, and its features The edge portion along the light-incident side of the light from the light source is provided with a chamfered surface between the end surface and the main surface, and the chamfered surface and the main surface are formed at an outer angle θ 1 of 45 In the following, the length L1 of the chamfered surface in the direction of the main surface is 5 μm or more, and the surface roughness Ra of the end surface is 0.5 μm or less.

According to this configuration, when the glass plate for a light guide plate is introduced from the end portion along the side along the light incident side, a sufficient amount of light can be introduced, and the glass plate is less likely to be chipped or broken. In other words, when a chamfered surface is formed on the edge portion of the side along the light incident side, it is possible to cope with the notch or breakage of the glass sheet, but the amount of introduction of light from the chamfered surface is reduced. Therefore, in the present invention, the outer angle θ 1 formed by the chamfered surface and the main surface is 45° or less, and the introduction of light can be sufficiently performed, and even if the chamfered surface having such an angle is formed, if the chamfered width is insufficient, it may be difficult. It does suppress the occurrence of gaps, breakage, and the like. Therefore, in the present invention, the length L1 of the chamfered surface in the direction along the main surface is 5 μm or more, and sufficient chamfer width is ensured, and generation of notches, breakage, and the like can be surely suppressed. Further, the end face of the end portion is a portion capable of greatly increasing the amount of light introduced compared to the chamfered surface. Therefore, in the present invention, the surface roughness Ra of the end face is 0.5 μm or less, and it is not easy to cause hindrance to the introduction of light due to the coarseness of the surface of the end face. According to the present invention, it is possible to provide a glass substrate for a light guide plate which not only solves the problem caused by the inherent characteristics of the glass plate, that is, is liable to cause chipping or breakage, and can easily satisfy the light guide plate. The necessary optical properties.

In the foregoing configuration, the end surface is a flat surface, and the end surface is The maximum separation dimension L2 of the imaginary vertical plane perpendicular to the main surface and in contact with the end surface is preferably 5% or less of the thickness of the glass sheet.

In this way, the end surface of the edge portion along the light-incident side is formed at a right angle or a substantially right angle to the main surface, so that the introduction of light from the end surface can be smoothly performed, and the introduction efficiency of the light amount to the glass substrate can be improved. .

In the above configuration, the end portion which is opposite to the side opposite to the light incident side has a chamfered surface between the end surface and the main surface, and the chamfered surface and the main surface form an outer angle θ 2 which exceeds 45° is preferred.

In this way, it is possible to reduce the edge of the opposite side of the side opposite to the light entrance side, and the strong light emission appears in a strip shape along the opposite side, that is, at the edge portion along the opposite side. If the external angle θ 2 formed by the chamfered surface and the main surface is 45° or less, the above phenomenon occurs clearly along the opposite side. Therefore, when the glass plate is used for the light guide plate, the light emission by the main surface, that is, the surface light emission may become uneven. However, if the aforementioned outer angle θ 2 exceeds 45°, the above phenomenon can be reduced, and the surface light emission can be made uniform.

In this case, the end portion which is opposite to the side opposite to the light incident side may have no chamfered surface between the end surface and the main surface.

As described above, since the chamfered surface does not exist as the cause of the above phenomenon, the phenomenon is surely reduced, and the uniformity of the surface luminescence when the glass sheet is used for the light guide plate is further promoted.

In the above configuration, the drawing direction of the glass sheet is along the traveling direction of light introduced from the edge portion of the side along the light incident side. Here, the "drawing direction" means forming from the molten glass as the glass In the process of the glass plate based on the glass plate, the direction in which the tension is applied.

As described above, even if foreign matter (defect) such as bubbles is mixed into the glass sheet, the foreign matter has a very high probability of being elongated and elongated in the drawing direction, so that it is less likely to hinder the progress of light introduced into the glass sheet. Therefore, the probability of adversely affecting the optical characteristics necessary for the light guide plate is extremely low.

Further, the present invention has a chamfered surface between the end surface and the main surface along the end side opposite to the side opposite to the light incident side from which the light from the light source is introduced, the chamfered surface and the main surface The outer angle θ 2 formed by the surface may be more than 45°.

The effects of the configuration described above are the same as those described above, and the description thereof will be omitted.

Further, the present invention may have a chamfered surface between the end surface and the main surface along the end side opposite to the side opposite to the light incident side from which the light from the light source is introduced.

The effects of the configuration described above are the same as those described above, and the description thereof will be omitted.

According to the present invention, it is possible to provide a glass substrate for a light guide plate which is less likely to be chipped or broken, and which can easily satisfy the optical characteristics necessary for the light guide plate.

1‧‧‧Glass plate for light guide plate

2‧‧‧Light guide plate

3‧‧‧Light source

7‧‧‧Main face

8‧‧‧Main face

9‧‧‧End edge (light entrance side edge)

10‧‧‧End edge (relative side edge)

12‧‧‧ end face

13‧‧‧Chamfered surface

13a‧‧‧Chamfered surface

14‧‧‧Chamfered surface

14a‧‧‧Chamfered surface

15‧‧‧Imaginary vertical plane

17‧‧‧ end face

18‧‧‧Chamfered surface

18a‧‧‧Chamfered surface

19‧‧‧Chamfered surface

19a‧‧‧Chamfered surface

20‧‧‧ imaginary vertical plane

[Fig. 1] is a schematic perspective view showing an arrangement state of a light guide plate used as a substrate with a glass plate for a light guide plate according to an embodiment of the present invention and a light source in which LEDs are arranged.

[Fig. 2] Fig. 2 is a perspective exploded view showing a detailed structure of an example of a light guide plate used as a substrate of a glass plate for a light guide plate according to an embodiment of the present invention.

[Fig. 3] is an enlarged view showing the shape of the periphery of the edge portion along the light incident side of the glass plate for a light guide plate according to the embodiment of the present invention, and in detail, is orthogonal to the side on the light incident side. And an enlarged cross-sectional view cut along the thickness direction.

[Fig. 4] is an enlarged view showing the shape of the periphery of the edge portion of the glass plate for a light guide plate according to the embodiment of the present invention which is opposite to the side on the light incident side, and in detail, An enlarged cross-sectional view in which the side on the light incident side is orthogonal to the opposite side and cut along the thickness direction.

[Fig. 5] is a view showing the principle of the occurrence of a phenomenon (light band phenomenon) which causes a problem in the past, and the periphery of the edge portion of the glass plate for a light guide plate facing the side opposite to the light incident side A partial cross-sectional view of the special part.

[Fig. 6] is a front view of a glass plate for a light guide plate schematically showing a state in which a phenomenon (light band phenomenon) of a conventional problem occurs.

[Fig. 7] Fig. 7 is a schematic cross-sectional view showing a portion of the peripheral portion of the glass plate for a light guide plate according to the second embodiment of the present invention along the light-incident side.

[Fig. 8] Fig. 8 is a view showing a light guide plate according to a third embodiment of the present invention. A schematic cross-sectional view of a portion of the peripheral shape of the edge portion of the glass plate along the light-incident side.

[Fig. 9] Fig. 9 is a partial cross-sectional view showing a peripheral shape of an edge portion along the light incident side of the glass plate for a light guide plate according to the fourth embodiment of the present invention.

[Fig. 10] Fig. 10 is a schematic cross-sectional view showing a portion of a peripheral portion of a glass plate for a light guide plate according to a fifth embodiment of the present invention, which is opposite to the side opposite to the light entrance side.

[Fig. 11] Fig. 11 is a schematic cross-sectional view showing a portion of a peripheral portion of a glass plate for a light guide plate according to a sixth embodiment of the present invention, which is opposite to the side opposite to the light entrance side.

[Fig. 12] Fig. 12 is a schematic cross-sectional view showing a portion of a peripheral portion of a glass plate for a light guide plate according to a seventh embodiment of the present invention, which is opposite to the side opposite to the light entrance side.

[Fig. 13] is a schematic perspective view for explaining a state of inspection of an embodiment of the present invention.

Hereinafter, a glass plate for a light guide plate according to an embodiment of the present invention and a method for producing the same will be described with reference to the accompanying drawings.

1 is a schematic perspective view showing an arrangement state of a light guide plate 2 used as a substrate and a light source 3 in which LEDs are arranged, which is a glass plate 1 for a light guide plate according to an embodiment of the present invention (hereinafter simply referred to as a glass plate 1). . As shown in the figure, at one end (lower end side) of the light guide plate 2, the light source 3 It is configured with a gap. The light guide plate 2 introduces light emitted from the light source 3 into the inside, and is emitted in a planar manner by total reflection in the internal propagation to cause surface light generation. The surface light-emitting device having the light source 3 and the light guide plate 2 is used, for example, as an edge type backlight of a liquid crystal display.

Fig. 2 is a perspective view showing a disassembled arrangement of a detailed structure of an example of the light guide plate 2. As shown in the figure, the light guide plate 2 includes a glass plate 1 serving as a substrate, a diffusion plate (including a diffusion film) 4 disposed on the front side of the glass plate 1, a crotch sheet 5, and a reflection disposed on the back side of the glass plate 1. Plate (including reflective film) 6. In the main surface 7 of one of the glass sheets 1, the diffusion plate 4 and the cymbal sheet 5 are sequentially attached by attaching or the like, and the reflection plate 6 is attached to the other main surface 8 by attaching or the like.

The glass plate 1 has an edge portion 9 (hereinafter referred to as a light-incident-side end portion 9) along the light-incident side that introduces light from the light source 3, and faces the side opposite to the light-incident side. The opposite side end portion 10 (hereinafter referred to as the opposite side end portion 10) and the side portion 11 which is paired with the light incident side end portion 9 and the opposite side end portion 10 are provided. Therefore, the main surface 7 of one of the glass sheets 1 is a light-emitting surface for emitting light emitted from the light-incident-side edge portion 9 to be surface-emitting, and the other main surface 8 of the glass sheet 1 is the same. The ground is a reflective surface for reflecting the introduced light. In the present embodiment, the thickness of the glass sheet 1 is 0.2 mm to 4.0 mm, preferably a lower limit of 0.3 mm or 0.4 mm and an upper limit of 3.0 mm or 2.0 mm.

The glass plate 1 of the present embodiment preferably contains, as a glass composition, SiO ₂ 40 to 80% (preferably 55 to 70%) and Al ₂ O ₃ 1 to 25% (preferably 2 to 2). 15%), B ₂ O ₃ 0~20% (preferably 5~15%), Na ₂ O 0~20% (preferably 5~16%), MgO 0~10%, CaO 0~15% (preferably 3 to 12%), SrO 0 to 15%, and BaO 0 to 35%. As described above, since the heat resistance is improved, it is difficult to change the size of the glass sheet 1 due to heat. Further, since the devitrification resistance is improved, the glass sheet 1 is easily formed.

Further, it is preferable to reduce the content of Fe ₂ O ₃ in the glass plate 1 as much as possible. When the content of Fe ₂ O ₃ is lowered, the maximum transmittance of the glass plate 1 in the wavelength range of 400 to 750 nm is improved, so that the luminance characteristics of the display device using the glass plate 1 can be improved. The content of Fe ₂ O ₃ in the glass plate 1 is preferably 50 ppm or less, 40 ppm or less, 30 ppm or less, 1 to 28 ppm, 5 to 25 ppm, and particularly preferably 10 to 22 ppm by mass. Moreover, if the content of Fe ₂ O ₃ is too small, the raw material cost will increase.

Fig. 3 is an enlarged view showing the shape of the periphery of the light-incident-side end portion 9 of the glass sheet 1, and is an enlarged cross-sectional view taken along the side of the light-incident side and cut along the thickness direction. As shown in the figure, the light incident side edge portion 9 of the glass sheet 1 has a chamfered surface 13 between the main surface 7 and the end surface 12, and is also between the other main surface 8 and the end surface 12. Has a chamfered surface 14. The outer angles θ 1 formed by the main faces 7, 8 and the chamfered faces 13, 14 are all 45 degrees or less. Further, the length L1 along the direction of the main faces 7 and 8 of the chamfered surfaces 13 and 14 is 5 μm or more. Further, the chamfered surfaces 13 and 14 are all polished surfaces, and the surface roughness Ra of the chamfered surfaces 13 and 14 is 1.0 μm or less.

In the present embodiment, the chamfered surfaces 13 and 14 are planes, and the end surface 12 is also a flat surface. Although the chamfered surfaces 13 and 14 are polished surfaces, the end surface 12 is The unpolished surface may also be an abrasive surface. Here, the term "unpolished surface" means that a scribe line is formed on the original glass sheet to break the obtained surface, or only a bending stress is applied to the original glass sheet to break the obtained surface, or It is a cut surface of a surface obtained by laser cutting of a raw glass plate by thermal stress.

The surface roughness Ra of the end surface 12 is preferably 0.5 μm or less. Further, the maximum separation dimension L2 of the end face 12 and the virtual vertical plane 15 which is perpendicular to the main faces 7 and 8 and which is in contact with the end face 12 is preferably 5% or less of the thickness T of the plate. Further, the length L3 of the end surface 12 in the direction orthogonal to the main faces 7, 8 is preferably 50% or more of the plate thickness T.

Further, the direction from the light-incident-side end portion 9 toward the opposite-side end portion 10 is preferably along the drawing direction of the glass sheet 1. That is, the drawing direction of the glass sheet 1 is along the traveling direction of the light introduced from the light incident side edge portion 9 (the left and right direction in the drawing). Here, the drawing direction of the glass sheet 1 means the direction in which the tensile force acts during the process of molding the glass sheet which is the basis of the glass sheet 1 from the molten glass. Therefore, defects (for example, air bubbles) 16 of foreign matter or the like mixed in the glass sheet 1 are elongated and elongated in the drawing direction of the glass sheet 1. Thus, the defect 16 has an elongated shape in the drawing direction of the glass sheet 1, and although it cannot be said that all the shapes of the defects are the same, the defect 16 having an elongated shape is far more than the defect having no elongated shape.

Fig. 4 is an enlarged view showing the shape of the periphery of the opposite side edge portion 10 of the glass sheet 1, and in detail, the side opposite to the light incident side is orthogonal to the opposite side and cut along the thickness direction. Expanded profile view. If As shown in the figure, the opposite side edge portions 10 of the glass sheet 1 have a chamfered surface 18 between the main surface 7 and the end surface 17 of one side, and also have a bottom surface between the other main surface 8 and the end surface 17. Corner 19 Preferably, each of the major faces 7, 8 and the chamfered faces 18, 19 has an outer angle θ 2 of more than 45°. Further, the length L4 along the direction of the main faces 7, 8 of the chamfered surfaces 18, 19 is preferably less than 30% of the sheet thickness T. Further, the chamfered surfaces 18 and 19 are all polished surfaces, and the surface roughness Ra of the chamfered surfaces 18 and 19 is 1.0 μm or less.

In the present embodiment, the chamfered surfaces 18 and 19 are planes, and the end surface 17 is also a flat surface. Although the chamfered surfaces 18 and 19 are polished surfaces, the end surface 17 may be an unpolished surface, and may be a polished surface. The meaning of the unpolished surface is as described above. The surface roughness Ra of the end surface 17 is preferably 0.5 μm or less. Further, the maximum separation dimension L5 of the end face 17 and the imaginary vertical plane 20 which is perpendicular to the main faces 7, 8 and which is in contact with the end face 17 is preferably less than 5% of the plate thickness dimension T. Further, the length L6 of the end surface 17 in the direction orthogonal to the main faces 7, 8 is preferably 30% or more of the thickness T of the plate. Further, the drawing direction of the glass sheet 1 is a defect along the traveling direction of the light introduced from the light-incident-side edge portion 9 (the horizontal direction in the drawing) or the foreign matter mixed in the glass sheet 1 (for example) The bubble 21 is an elongated shape elongated in the drawing direction of the glass sheet 1, as described above.

The pair of side portions 11 may have a cross-sectional shape that is perpendicular to the side and cut along the thickness direction, and may have a chamfered surface between the main faces 7 and 8 and the end faces, and may have no chamfered surface. The unpolished surface or the polished surface may be a curved surface that is curved such as an arc.

Next, the effect of the glass plate 1 having the above configuration will be described.

First, the effect of the peripheral structure based on the light-incident-side end portion 9 shown in Fig. 3 will be described. Since the chamfered surfaces 13 and 14 are formed on the light-incident side edge portion 9, the glass plate 1 can be handled with a gap or breakage, but it is difficult to introduce light from the chamfered surfaces 13 and 14. On the other hand, in the present embodiment, the outer angles θ 1 formed by the chamfered surfaces 13 and 14 and the main surfaces 7 and 8 are both 45° or less, and the introduction of light can be sufficiently performed. At least one of θ 1 is preferably 40° or less, 35° or less, 30° or less, 20° or less, or 15° or less, and may be 10° or less or 5° or less. However, from the viewpoint of suppressing the chipping or breakage of the glass sheet 1, it is preferably 3 or more.

Further, even if the chamfered surfaces 13 and 14 having the outer angle θ 1 as described above are formed, if the respective chamfer widths S1 are insufficient, it may be difficult to reliably suppress the occurrence of chipping or breakage of the glass sheet 1. On the other hand, in the present embodiment, the length L1 of the chamfered surfaces 13 and 14 in the direction along the main faces 7 and 8 is 5 μm or more, so that a sufficient chamfer width S1 is secured, and the glass plate 1 can be surely suppressed. Gap or breakage, etc. From this viewpoint, at least one of the lengths L1 is preferably 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more, and may be 35 μm or more or 40 μm or more. However, from the viewpoint of sufficiently introducing light from the end surface 12, it is preferably 200 μm or less or 100 μm or less.

Further, the end surface 12 of the light-incident-side end portion 9 is a portion capable of greatly increasing the amount of light introduced compared to the chamfered surfaces 13 and 14. therefore, In the present embodiment, the surface roughness Ra of the end surface 12 is 0.5 μm or less, and it is not easy to cause the introduction of light due to the thick surface roughness of the end surface 12. From this viewpoint, the surface roughness Ra of the end surface 12 is preferably 0.3 μm or less, 0.1 μm or less, 0.08 μm or less, 0.07 μm or 0.06 μm or less, more preferably 0.05 μm or less. Further, in the present embodiment, the surface roughness Ra is also 1.0 μm or less with respect to the chamfered surfaces 13 and 14, and the amount of light introduced from the chamfered surfaces 13 and 14 is increased. Therefore, the surface roughness Ra of at least one of the chamfered surfaces 13 and 14 is preferably 0.5 μm or less, 0.1 μm or less, 0.08 μm or less, 0.07 μm or less, or 0.06 μm or less, more preferably 0.05 μm or less.

Further, when the maximum separation dimension L2 of the end surface 12 and the virtual vertical plane 15 is shortened, the amount of light introduced from the end surface 12 can be efficiently increased. In the present embodiment, the maximum separation dimension L2 is 5% or less of the thickness T of the sheet thickness, so that the efficiency of increasing the amount of introduced light is increased. From this viewpoint, the maximum separation dimension L2 is preferably 4% or less, 3% or less, or 2% or less of the thickness T of the sheet, and more preferably 1% or less.

Further, when the length L3 of the end surface 12 in the direction orthogonal to the main faces 7 and 8 is increased, the amount of light introduced from the end face 12 can be efficiently increased. In the present embodiment, the length L3 is set to 50% or more of the thickness T of the sheet thickness, so that the efficiency of increasing the amount of introduced light is increased. From this viewpoint, the length L3 is preferably 55% or more, 60% or more, 65% or more, or 70% or more, and may be 75% or more or 80% or more. However, from the viewpoint of suppressing the chipping or breakage of the glass sheet 1, it is 95%. Below or below 90% is preferred.

Further, when the drawing direction of the glass sheet 1 is not along the traveling direction of the light introduced from the light-incident side edge portion 9, the length direction of the elongated defect 16 mixed in the glass sheet 1 does not follow the above-mentioned light. The direction of travel. Therefore, the above-described travel of light may be hindered by the defect 16 of the elongated shape. Here, in the present embodiment, the pulling direction of the glass sheet 1 is along the above-described light traveling direction, and such a problem can be effectively avoided.

According to the above-described embodiment, the light-incident-side end portion 9 not only solves the problem caused by the inherent characteristics of the glass sheet 1, that is, it is likely to cause chipping or breakage, and the glass sheet 1 is sufficiently It has the optical characteristics necessary for the light guide plate 2.

First, the effect of the structure based on the periphery of the opposite side end portion 10 shown in FIG. 4 will be described. Since the chamfered surfaces 18 and 19 are formed on the opposite side end portions 10, it is possible to cope with the notch or breakage of the glass sheet 1, but it may occur along the longitudinal direction of the opposite side end portions 10. The phenomenon of strong luminescence (hereinafter referred to as the phenomenon of light band). This light band phenomenon is considered to be reflected from the light incident side edge portion 9 and reaches the opposite side edge portion 10 at the chamfered surface 19 (18) as shown in Fig. 5, and the reflected light is reflected. It is caused by collecting light at the periphery of the opposite side end portion 10. Therefore, as shown in Fig. 6, when the light 22 enters the light from the light incident side edge portion 9 to the inside of the glass sheet 1 and travels toward the opposite side end portion 10, it may be as the opposite side end portion 10 The vicinity of the light band phenomenon as shown by the dotted line. In the glass plate 1 which will produce the phenomenon of the light band When the light guide plate 2 is used, the light emission by the main surfaces 7, 8 or the surface light emission may become uneven. Such a problem is clearly caused when the outer angles θ 2 of the chamfered surfaces 18 and 19 and the main surfaces 7 and 8 are both 45° or less.

On the other hand, in the present embodiment, since each of the external angles θ 2 exceeds 45°, the light band phenomenon occurring in the opposite side edge portion 10 is reduced, and the uniformity of the surface light emission of the light guide plate 2 is less likely to be hindered. From this point of view, it is preferable that at least one of the aforementioned external angles θ 2 exceeds 50°, exceeds 60°, or exceeds 70°, and may exceed 80° or exceed 90°.

Further, even if the chamfered surfaces 18 and 19 having the outer angle θ 2 as described above are formed, if the chamfered width S2 is excessively large, the optical band phenomenon or the chamfering surfaces 18 and 19 cannot be sufficiently reduced. Become complicated. Here, in the present embodiment, since the length L4 of the chamfered surfaces 18 and 19 along the main faces 7 and 8 is less than 30% of the thickness T, it is possible to prevent the chamfered width S2 from becoming excessive. From this point of view, at least one of the lengths L4 is preferably less than 25% or 20% of the sheet thickness T, and may not be 15% or 10% of the sheet thickness T.

Further, it is preferable that the end surface 17 of the opposing side edge portion 10 has a surface roughness Ra equal to the end surface 12 of the light-incident-side edge portion 9 in terms of the grade of the glass sheet 1. Therefore, in the present embodiment, the surface roughness Ra of the end surface 17 of the opposing side edge portion 10 is 0.5 μm or less, 0.1 μm or less, 0.08 μm or less, 0.07 μm or less, or 0.06 μm. The following may be used, and may be 0.05 μm or less. Therefore, from the same point of view, although the opposite side end portion 10 is turned down The surface roughness Ra of the corner faces 18 and 19 is 1.0 μm or less, and at least one of the chamfered faces 18 and 19 has a surface roughness Ra of 0.5 μm or less, 0.1 μm or less, 0.08 μm or less, 0.07 μm or 0.06. The thickness may be not more than μm, and may be 0.05 μm or less.

Further, when the maximum separation dimension L5 of the end surface 17 of the opposing side edge portion 10 and the virtual vertical surface 20 is increased, there is a possibility that the optical characteristics are disturbed. Here, in the present embodiment, the maximum separation dimension L5 is 5% or less of the thickness T of the sheet, and it is possible to surely prevent the end surface 17 from becoming a main cause of deterioration in optical characteristics. In addition, from the viewpoint of ensuring the grade of the sheet glass, the maximum separation dimension L5 may be 4% or less, 3% or less, or 2% or less of the thickness T of the sheet, and may be 1% or less. .

Further, when the length L6 of the end surface 17 in the direction orthogonal to the main surfaces 7 and 8 is shortened, if the chamfer width S2 is too long, there is a possibility that the occurrence of the light band phenomenon cannot be surely prevented, or The processing of the chamfered surfaces 18, 19 becomes complicated. Here, in the present embodiment, the length L6 is 30% or more of the thickness T of the sheet thickness, and may be 40% or more, 50% or more, 60% or more, or 70% or more, and further 80% or more. Or 90% or more.

According to the above-described improvement, in the present embodiment, the problem of the inherent characteristics of the glass sheet 1 is solved in the opposite side end portion 10, that is, the gap or breakage is likely to occur, and the light belt is provided. The phenomenon is less likely to occur, and the surface light emission of the light guide plate 2 can be made uniform.

Further, in the above-described embodiment, the end faces 12 and the chamfered faces 13, 14 of the light incident side edge portion 9 are flat, and the opposite side edges are provided. The end face 17 and the chamfered faces 18, 19 of the portion 10 are also flat, but the present invention can be variously modified as shown below.

The light-incident-side end portion 9 shown in FIG. 7 has a convex curved surface, and a chamfered surface 13 formed of a flat surface is formed between the end surface 12 and the main surfaces 7 and 8, respectively. 14. In this case, the light-incident-side end portion 9 is an end surface which is curved in an arc shape or the like, and the chamfered surface is not formed.

The light-incident-side end portion 9 shown in Fig. 8 has no chamfered surface between the end surface 12 (unpolished surface or polished surface) and the main surfaces 7, 8. At this time, the opposite side edge portion 10 outside the drawing is formed between the end surface 17 and the main surfaces 7 and 8 as described above or below, and chamfered surfaces 18 and 19 (18a, as described above or later) are formed. 19a).

The light incident side edge portion 9 shown in Fig. 9 is formed with R chamfered surfaces 13a and 14a between the end surface 12 formed by the flat surface and the main surfaces 7 and 8, respectively. The radius of curvature of each of the R chamfered surfaces 13a and 14a is preferably 20% or less, 15% or less, or 10% or less of the sheet thickness T, and the lower limit is 5%, 3% or 1%. It is better.

In the opposite side end portion 10 shown in FIG. 10, the end surface 17 is a convex curved surface, and a chamfered surface 18 formed by a plane is formed between the end surface 17 and the main surfaces 7 and 8, respectively. 19. At this time, in the opposite side end portion 10, all the regions between the two main faces 7 and 8 are end faces that are curved in an arc shape or the like, and a chamfered surface may not be formed.

The opposite side edge portion 10 shown in Fig. 11 has no chamfering between the end surface 17 (unpolished surface or polished surface) and the main surfaces 7, 8. surface. At this time, the light-incident side edge portion 9 outside the drawing is formed between the end surface 12 and the main surfaces 7 and 8 as described above, and the chamfered surfaces 13 and 14 (13a, 14a) are formed as described above.

The opposite side end side portion 10 shown in Fig. 12 is formed with R chamfered surfaces 18a and 19a between the end surface 17 formed of a flat surface and the main surfaces 7 and 8, respectively. The radius of curvature of each of the R chamfered surfaces 18a and 19a is preferably 20% or less, 15% or less, or 10% or less of the sheet thickness T, and the lower limit is 5%, 3% or 1%. It is better.

Further, in the above embodiment, one of the four sides of the glass sheet 1 may be the light-incident side edge portion 9, and the adjacent two sides or three sides or all the sides may be the light-incident side edge portions 9.

[Example 1]

As the sample of Example 1, four glass plates each having a longitudinal dimension of 400 mm, a lateral dimension of 300 mm, and a plate thickness of 2.0 mm were prepared. For the four glass sheets, the outer angles θ 1 formed by the chamfered surfaces 13 and 14 of the light incident side edge portion 9 shown in Fig. 3 and the main surfaces 7 and 8 are 35° and 45°, respectively. For 55° or 65°, these were used as samples No. 1 to 4. With respect to the sample Nos. 1 to 4, as shown in Fig. 13, the light of the light source 23 formed by the free halogen lamp is emitted through the diffusion plate, and the emitted light is introduced from the glass plate 1 of each sample. The light side end portion 9 is introduced and evaluated by measuring the illuminance by the illuminometer 24 abutting against the side edge portion 10. At this time, the opposing side edge portion 10 is an unpolished surface having no chamfered surface in all of the samples. Further, the traveling direction of the light is the longitudinal direction (the pulling direction) of the glass sheet. The results are shown in Table 1 below. In addition, the "decline rate" in Table 1 means the illuminance measured by the illuminometer similarly to the glass plate of the unpolished surface which does not have a chamfering surface with respect to the light-increasing-side edge part 9, and each The rate of decrease in illuminance measured by the sample.

[Embodiment 2]

As the sample of Example 2, four glass sheets having the same size and the same thickness as the sample of Example 1 were prepared. For each of the four glass sheets, the maximum separation dimension L2 of the end surface 12 of the light-incident-side end portion 9 shown in Fig. 3 and the virtual vertical surface 15 is 0.05 mm (2.5% of the sheet thickness) and 0.10 mm, respectively. (5.0% of the sheet thickness), 0.15 mm (7.5% of the sheet thickness), and 0.20 mm (10% of the sheet thickness) were used as the sample Nos. 5 to 8. With respect to the sample Nos. 5 to 8, as shown in Fig. 13, the illuminance was measured by the illuminometer 24 in the same manner as in the first embodiment, and evaluated. The results are shown in Table 2 below. In addition, the "decline rate" in Table 2 means the illuminance measured by the illuminometer 24 provided in the same position as the position shown in Fig. 13 in a state where the glass plate is not present, and is used for each sample. The measured decrease in illuminance.

[Example 3]

As a sample of Example 3, a plurality of glass plates having a longitudinal dimension of 130 mm, a lateral dimension of 65 mm, and a plate thickness of 1.1 mm were prepared. These plurality of glass sheets are classified into those manufactured by the floating method and those produced by the overflow down-draw method. First, in the glass plate which was produced by each method, it was investigated by the light irradiation inspection of 2000 lux, and it was investigated whether the long diameter (the longitudinal direction dimension of the bubble) of the bubble which is a defect is 300 micrometer or more, and it is not including a long diameter. A group of glass plates having bubbles of 300 μm or more is referred to as Group A, and a group of glass plates including bubbles having a long diameter of 300 μm or more is referred to as Group B. Further, for the glass plates of the B group, the correlation between the long diameter of the bubble and the longitudinal direction of the bubble and the drawing direction of the glass plate was examined. The results of the inspection are shown in Table 3 below.

According to the above Table 3, the long-diameter bubble which greatly affects the diffusion has a higher percentage of the longitudinal direction of the bubble parallel to the drawing direction of the glass plate than the bubble having a shorter long diameter.

Next, the glass plates of the above-mentioned Group A and Group B were evaluated by measuring the illuminance by the illuminometer 24 in the same manner as in Example 1 as shown in Fig. 13 . At this time, the measurement of the illuminance is divided into a case where the drawing direction of the glass plates of the A group and the B group is orthogonal to the traveling direction (incidence direction) of the light, and a case where the direction of the light is parallel. Further, the drawing direction of the glass sheet can be specified from the twisted state of the main surface or the like. The measurement results of this case are shown in Table 4 below. In addition, "%" in Table 4 indicates the transfer efficiency, and the "transfer efficiency" means the ratio of the illuminance of the light actually passing through the glass plate based on the original illuminance (29000 lux) of the light source at the measurement position. .

According to the above Table 4, both the A group and the B group glass plate have the incident direction parallel to the drawing direction, and the transfer efficiency is higher than when the two directions are orthogonal. Further, in the case where the incident direction is parallel to the drawing direction, a group A composed of a glass plate having few defects in which small bubbles are mixed, and a glass plate having a large number of defects in which large bubbles are mixed are formed. Group B is able to achieve the same transfer efficiency. This means that if the incident direction is parallel to the pulling direction, the transfer efficiency is high regardless of the size of the defect (bubble). Further, since the glass plate produced by the floating method has a lower transmittance than the glass plate produced by the overflow down-draw method, a difference occurs between the two.

1‧‧‧Glass plate for light guide plate

7‧‧‧Main face

8‧‧‧Main face

9‧‧‧End edge (light entrance side edge)

12‧‧‧ end face

13‧‧‧Chamfered surface

14‧‧‧Chamfered surface

15‧‧‧Imaginary vertical plane

16‧‧‧ Defects

Claims (7)

A glass plate for a light guide plate, characterized in that an edge portion along a side of a light incident side that introduces light from a light source is provided with a chamfered surface between the end surface and the main surface, the chamfered surface and the main surface The outer surface angle θ 1 is 45° or less, the length L1 of the chamfered surface in the direction of the main surface is 5 μm or more, and the surface roughness Ra of the end surface is 0.5 μm or less. The glass plate for a light guide plate according to claim 1, wherein the end surface is a flat surface, and the maximum separation dimension L2 of the end surface and an imaginary vertical plane perpendicular to the main surface and contacting the end surface is The sheet thickness of the glass sheet is 5% or less. The glass plate for a light guide plate according to the first or second aspect of the invention, wherein the edge portion opposite to the side opposite to the light incident side is provided between the end surface and the main surface The chamfered surface has an outer angle θ 2 of more than 45° with the main surface. The glass plate for a light guide plate according to the first or second aspect of the invention, wherein the edge portion opposite to the side opposite to the light incident side is between the end surface and the main surface. Has a chamfered surface. The glass plate for a light guide plate according to any one of claims 1 to 4, wherein the drawing direction of the glass plate is along a side along the light incident side The direction of travel of the light introduced by the edge. A glass plate for a light guide plate characterized in that a side edge portion opposite to a side opposite to a light incident side that introduces light from a light source is provided with a chamfered surface between the end surface and the main surface, The chamfered surface and the aforementioned main surface form an outer angle θ 2 of more than 45°. A glass plate for a light guide plate characterized in that a side edge portion opposite to a side opposite to a light incident side that introduces light from a light source is not provided with a chamfered surface between the end surface and the main surface.