KR20180020120A - Light guide plate - Google Patents

Abstract

The light guide plate of the present invention has at least a glass plate, the content of Rh ₂ O _{3 in} the glass plate is less than 1 ppm by mass, and the difference in transmittance between the maximum transmittance and the minimum transmittance in the optical path length of 100 mm and the wavelength range of 400 to 750 nm 12% or less.

Description

Light guide plate

The present invention relates to a light guide plate, and more particularly to a light guide plate suitable for an edge light type surface light emitting device.

Conventionally, a liquid crystal display device is used for a liquid crystal television or the like. The liquid crystal display device includes a surface light emitting device and a liquid crystal panel disposed on the light emitting surface side of the surface light emitting device. As a surface emitting device, for example, a direct type and an edge light type are known.

In the direct underlying type surface emitting device, the light source is arranged on the back surface which is opposite to the light output surface. When a point light source such as a light emitting diode is used as a light source, a large number of LED chips are required to compensate for the brightness, and the deviation of the luminance characteristic becomes very large.

For this reason, edge light type surface light emitting devices are mainly used at present. In the edge light type surface emitting device, a light source such as an LED, a light guide plate, and a reflective layer such as a reflective film are provided. The light source is disposed on an end surface which is orthogonal to the light exit surface (surface). The light guide plate is arranged to introduce light from the light source from the end face, propagate inside by total internal reflection, and exit in a planar form from the light exit face. A resin plate such as an acrylic resin is generally used as a light guide plate (see Patent Documents 1 to 4). The reflecting layer is disposed on the rear side opposite to the light emitting surface so as to reflect the light that has escaped to the back surface and to emit light on the display surface of the liquid crystal panel or the like. In addition, in order to uniformly emit light on the display surface of a liquid crystal panel or the like, a diffusion layer may be disposed on the light exit surface side of the light guide plate.

Fig. 1 is a schematic cross-sectional view showing an example of the edge light type surface light emitting device 1. Fig. The edge light type surface emitting device 1 includes a light source 2 such as an LED, a light guide plate 3, a reflective layer 4, and a diffusion layer 5. Light from the light source 2 is incident on the end face of the light guide plate 3 and propagates inside the light guide plate 3. The light reaching the light reflection surface 6 is reflected by the reflection layer 4 and travels toward the light emission surface 7 and is diffused by the diffusion layer 5. As a result, the display surface of the liquid crystal panel or the like disposed above the diffusion layer 5 can be uniformly emitted. A reflective layer may be formed on the end surface of the light guide plate 3 opposite to the end surface of the light guide plate 3, from which the light from the light source 2 is incident.

Japanese Patent Laid-Open Publication No. 2012-123933 Japanese Patent Application Laid-Open No. 12-138345 Japanese Patent Application Laid-Open No. 2012-216523 Japanese Patent Application Laid-Open No. H02-216528

In the edge light type surface light emitting device, when light is generated from the light source, heat is generated, and accordingly, the temperature of the light guide plate also rises. When a resin plate is used as the light guide plate, the dimensional change caused by the heat of the light guide plate becomes larger than the dimensional change of the liquid crystal panel. This is because the resin plate has a high coefficient of thermal expansion. For example, the coefficient of thermal expansion of an acrylic resin plate is about 700 x 10 < ^-7 > / deg. Therefore, conventionally, voids are formed in the edge portion of the frame of the liquid crystal display device so as not to cause undue stress due to the difference in dimensional change, and the dimensional change of the light guide plate is corrected.

However, in recent years, it has become difficult to correct the dimensional change of the light guide plate at the edge portion of the frame of the liquid crystal display device by the tightening softening of the liquid crystal display device.

When a resin plate is used as the light guide plate, the amount of light is reduced when the light from the light source is incident on the end face and escapes to the light exit face. As a result, the luminance characteristic of the display device is likely to deteriorate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is a technical object of the present invention to provide a light guide plate which is less prone to change in dimensions due to a rise in temperature and is difficult to deteriorate the luminance characteristics of the display device.

As a result of intensive investigations, the inventors of the present invention have found that, by adopting a glass plate whose dimensional change due to temperature change is small as a light guide plate, reducing the content of Rh ₂ O _{3 in} the glass plate and regulating the transmittance of the glass plate to a predetermined range, And found out that the present invention can solve the problem. That is, the light guide plate of the present invention has at least a glass plate, the content of Rh ₂ O _{3 in} the glass plate is less than 1 ppm by mass, and the maximum transmittance and the minimum transmittance of the glass plate at the optical path length of 100 mm and the wavelength range of 400 to 750 nm And the difference in transmittance is 12% or less. Here, the " maximum transmittance and minimum transmittance in the optical path length of 100 mm and the wavelength range of 400 to 750 nm " can be measured by a commercially available transmittance measuring apparatus and can be measured, for example, by UV-3100PC manufactured by Shimadzu Corporation. The " transmittance " indicates the internal transmittance calculated by Equation 1, unless otherwise specified.

[Equation 1]

_{logT in = log (I 1 /} I 0) -logR

logT _in : internal transmittance (%)

I ₀ : Intensity of incident light (%)

I ₁ : Intensity (%) of light after passing through a specific optical path length

R: Decay rate of light due to reflection (%)

A display panel such as a liquid crystal panel has a structure in which a display element such as a liquid crystal element is sandwiched between a pair of glass plates. Therefore, when a glass plate is employed as the light guide plate, a difference in dimensional change between the display panel and the light guide plate is reduced, and thus it is possible to appropriately cope with the dilution softening of a display device such as a liquid crystal display device.

The inventor of the present invention has found that when the difference in transmittance of the glass plate in the visible region is small, the luminance characteristic of the display device is improved. Further, the inventors of the present invention have found that Rh ₂ O ₃ in a glass plate greatly influences absorption at a wavelength of about 450 nm, and when the content is reduced, the difference in transmittance of the glass plate in the visible region can be suitably reduced. Based on these findings, in the present invention, the content of Rh ₂ O ₃ in the glass plate is regulated to be less than 1 ppm by mass, and the transmittance of the maximum transmittance and the minimum transmittance of the glass plate at an optical path length of 100 mm and a wavelength range of 400 to 750 nm The luminance of the display device is remarkably increased by regulating the amount of the vehicle to 12% or less.

Secondly, it is preferable that the light guide plate of the present invention has a content of Fe ₂ O _{3 in} the glass plate of less than 50 ppm by mass and a maximum transmittance of 85% or more at an optical path length of 100 mm and a wavelength range of 400 to 750 nm . When the content of Fe ₂ O ₃ in the glass plate is reduced, the maximum transmittance of the glass plate at the optical path length of 100 mm and the wavelength range of 400 to 750 nm can be increased. Fe ₂ O ₃ exists in the form of Fe ^{3 +} or Fe ^{2 + in} the glass. Thereby reducing the Fe ^{3 +} is a transmittance in the visible range of wavelengths to have an absorption peak in the vicinity of 380㎚, ultraviolet region, the short wavelength side. Fe ^{2 +} having an absorption peak at a wavelength 1080㎚, to lower the transmittance in the visible range of the long wavelength side. Therefore, when the content of Fe ₂ O ₃ is increased, the maximum transmittance at a wavelength of 400 to 750 nm and an optical path length of 100 mm is likely to decrease. The glass plate generally contains a large amount of Fe ₂ O ₃ mixed in the glass raw material or the manufacturing process. Therefore, since the conventional glass sheet has a large content of Fe ₂ O ₃ , it is difficult to enhance the luminance characteristic of the display device. Therefore, if the content of Fe ₂ O _{3 in} the glass plate is regulated to be less than 50 ppm by mass, the luminance characteristic of the display device can be enhanced. In the present invention, " Fe ₂ O ₃ " includes bivalent iron oxide and trivalent iron oxide, and bivalent iron oxide is treated in terms of Fe ₂ O ₃ . For other oxides, it is assumed that the oxide is treated on the basis of the same oxide.

Third, it is preferable that the content of Cr ₂ O _{3 in} the glass plate of the light guide plate of the present invention is 5 ppm or less by mass. According to the investigation by the present inventor, Cr ₂ O ₃ in the glass plate greatly influences the absorption near the wavelength of 630 nm, and if the content is reduced, the difference in transmittance of the glass plate in the visible region can be effectively reduced.

Fourth, the light guide plate of the present invention preferably has a dot shape printed on one surface (preferably a light output surface) of the glass plate. This makes it easier to make the light emitted from the light output surface uniform in the plane.

Fifthly, it is preferable that the light guide plate of the present invention gradually increases as the dot-shaped dot diameter moves away from the end surface where light from the light source should enter. This makes it easier to make the light emitted from the light output surface uniform in the plane.

Sixth, the light guide plate of the present invention preferably has an average surface roughness Ra of 0.5 μm or less at an end face (preferably, an end face on which light from a light source should enter) of the glass plate. This makes it easier to reduce the optical loss when the light from the light source enters the end face.

Seventhly, in the light guide plate of the present invention, it is preferable that a reflective layer is formed on all or a part of the end surface other than the end surface on which the light from the light source should enter. This makes it difficult for the light propagated inside the glass plate to leak from the end face.

2 is a conceptual perspective view showing an example of a light guide plate of the present invention. As shown in Fig. 2, the light guide plate 10 is provided with a glass plate 11. As shown in Fig. Light from the light source 12 is incident on the end face 13 of the glass plate 11 and propagates inside the glass plate 11 to be emitted from the light output face. Here, the content of Rh ₂ O _{3 in} the glass plate 11 is less than 1 ppm by mass, and the difference in transmittance between the maximum transmittance and the minimum transmittance in the optical path length of 100 mm and the wavelength range of 400 to 750 nm of the glass plate 11 is 12 % Or less. A dot shape 15 is formed on the back surface 14 opposite to the light exit surface of the glass plate 11. The dot diameter of the dot shape 15 gradually increases from the end surface 13 toward the end surface 16. The light emitted from the light emitting surface is uniformed in the surface by this dot shape 15. A reflective layer 19 is formed on the end surfaces 16, 17, and 18 of the glass plate, respectively. The light reaching the end faces 16, 17, 18 of the glass plate is reflected by the reflective layer 19 and returns to the inside of the glass plate 11, and ultimately exits from the light exit face.

It is also possible to use a plurality of glass plates 11 of the present invention bonded together. For example, two glass plates 11 may be prepared, a reflective layer may not be formed on the end surface 17 of one glass plate 11, and a reflective layer may not be formed on the end surface 18 of the other glass plate 11, It is possible to manufacture a light guide plate having a large area by joining the end faces without forming the reflective layers on both sides with a transparent adhesive having a matching index of refraction.

In the eighth aspect, the light guide plate of the present invention is characterized in that the glass plate contains 40 to 80% of SiO ₂ , 1 to 15% of Al ₂ O ₃ , 0 to 20% of B ₂ O _3, 0 to 20% of Na ₂ O, 0 to 10% of MgO, 0 to 15% of CaO, 0 to 15% of SrO and 0 to 35% of BaO. In this case, the coefficient of thermal expansion of the glass plate tends to be lowered.

Ninthly, it is preferable that the glass plate of the light guide plate of the present invention has a thermal expansion coefficient of 120 x 10 < ^-7 > / DEG C or less. Here, the "thermal expansion coefficient" refers to a value obtained by measuring the average thermal expansion coefficient at 30 to 380 ° C in accordance with JIS R3102 using a dilatometer.

[0040] In the tenth aspect, the light guide plate of the present invention is preferably used in an edge light type surface light emitting device.

Eleventh, the glass plate of the present invention is characterized by having a maximum transmittance of 93% or more at an optical path length of 500 mm and a wavelength range of 400 to 750 nm.

Twelfth, the glass plate of the present invention preferably has a content of Rh ₂ O ₃ of less than 1 ppm by mass and a content of Fe ₂ O ₃ of 10 ppm or less by mass.

A thirteenth aspect of the present invention is the glass plate of the present invention, wherein the difference in transmittance between the maximum transmittance and the minimum transmittance in a wavelength range of 400 to 750 nm is 6% or less.

Fourteenthly, it is preferable that the glass plate of the present invention contains Cr ₂ O ₃ and Fe ₂ O ₃ in the glass composition, and the Cr ₂ O ₃ / Fe ₂ O ₃ ratio by mass is 0.01 to 0.13. By regulating the mass ratio Cr ₂ O ₃ / Fe ₂ O ₃ within the above range, the difference in transmittance between the maximum transmittance and the minimum transmittance in the wavelength range of 400 to 750 nm can be reduced as much as possible.

Fifteenth, in the glass plate of the present invention, the content of Fe ₂ O _{3 in} the glass composition is preferably 1 to 10 ppm by mass.

Sixteenth, the glass plate of the present invention preferably has a maximum transmittance of 93% or more at an optical path length of 500 mm and a wavelength range of 400 to 750 nm.

Seventeenthly, it is preferable that the glass plate of the present invention has an optical path length of 0.15 mm and a transmittance of 85% or more at a wavelength of 250 nm.

1 is a schematic cross-sectional view showing an example of an edge light type surface emitting device.
2 is a conceptual perspective view showing an example of a light guide plate of the present invention.
Fig. 3 is a data showing a transmittance curve at a wavelength of 400 to 750 nm in an optical path length of 500 mm of a sample in the column of Example 2. Fig.
4 is data showing a transmittance curve (internal transmittance curve) at a plate thickness of 0.15 mm and a wavelength range of 200 to 700 nm of the sample in the column of Example 3. Fig.
5 is data showing the external transmittance curve at a plate thickness of 0.15 mm and a wavelength range of 200 to 700 nm in the column of Example 3.

In the light guide plate of the present invention, the difference in transmittance between the maximum transmittance and the minimum transmittance in the optical path length of 100 mm and the wavelength range of 400 to 750 nm is preferably 12% or less, 10% or less, 8% or less, 5% or less, especially 4% or less. If the difference in transmittance is too large, the luminance characteristic of the display device tends to be lowered.

The maximum transmittance at the optical path length of 100 mm and the wavelength range of 400 to 750 nm is preferably 88% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% , 97% or more, 98% or more, particularly 99% or more. If the maximum transmittance is too low, the luminance characteristic of the display device tends to be lowered.

The maximum transmittance at an optical path length of 200 mm and a wavelength range of 400 to 750 nm is preferably at least 86%, at least 88%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94% , 96% or more, 97% or more, 98% or more, particularly 99% or more. If the maximum transmittance is too low, the luminance characteristic of the display device tends to be lowered.

The maximum transmittance at an optical path length of 500 mm and a wavelength range of 400 to 750 nm is preferably at least 85%, at least 86%, at least 88%, at least 90%, at least 91%, at least 92% , 95% or more, 96% or more, 97% or more, 98% or more, particularly 99% or more. If the maximum transmittance is too low, the luminance characteristic of the display device tends to be lowered.

In the light guide plate of the present invention, the maximum transmittance of the glass plate at the optical path length of 100 mm and the wavelength range of 400 to 750 nm is 85% or more, preferably 87% or more, 88% or more, 89% or more, to be. If the maximum transmittance is too low, the luminance characteristic of the display device tends to be lowered.

The content of Rh ₂ O _{3 in} the glass plate is less than 1 ppm by mass, preferably 0.8 ppm or less, 0.6 ppm or less, 0.01 to 0.5 ppm, 0.05 to 0.4 ppm, particularly 0.1 to 0.3 ppm. If the content of Rh ₂ O ₃ is excessively large, the difference in transmittance between the maximum transmittance and the minimum transmittance in a wavelength range of 400 to 750 nm tends to be excessive. If the content of Rh ₂ O ₃ is too small, it becomes difficult to use a high-strength Pt-Rh alloy in a glass manufacturing facility, thereby increasing the production cost of the glass plate.

In order to reduce the content of Rh ₂ O ₃ as much as possible, it is possible to use a high-purity glass raw material, adjust the glass production conditions so as not to contain Rh ₂ O ₃ , or reduce the use of Pt-Rh alloy in the glass production facility .

The content of Cr ₂ O _{3 in} the glass plate is preferably 5 ppm or less, 4 ppm or less, 3 ppm or less, 0.1 to 1.5 ppm, 0.2 to 1 ppm, particularly 0.3 to 0.8 ppm in mass. If the content of Cr ₂ O ₃ is excessively large, the difference in transmittance between the maximum transmittance and the minimum transmittance in a wavelength range of 400 to 750 nm tends to be excessive. If the content of Cr ₂ O ₃ is too small, the cost of the raw material and the cost of producing the glass plate are increased.

The content of Fe ₂ O _{3 in} the glass plate is preferably 50 ppm or less, 40 ppm or less, 30 ppm or less, 28 ppm or less, 25 ppm or less, 22 ppm or less, 20 ppm or less, 18 ppm or less, 15 ppm or less, 12 ppm or less, 10 ppm or less, 6 ppm or less, particularly 1 to 5 ppm. If the content of Fe ₂ O ₃ is excessively large, the maximum transmittance at a wavelength of 400 to 750 nm and an optical path length of 100 mm is likely to be lowered. Further, when the content of Fe ₂ O ₃ is less than 1 ppm by mass, it becomes difficult to reduce the difference in transmittance between the maximum transmittance and the minimum transmittance in the wavelength range of 400 to 750 nm.

The transmittance near a wavelength of 550 nm is relatively high in a wavelength range of 400 to 750 nm and the transmittance near a wavelength of 400 nm and a wavelength of 750 nm is likely to be relatively lower. Therefore, when the transmittance near the wavelength of about 400 nm and the wavelength of about 750 nm is increased while slightly lowering the transmittance near the wavelength of 550 nm, the difference in transmittance between the maximum transmittance and the minimum transmittance in the wavelength range of 400 to 750 nm can be reduced as much as possible. According to the investigation conducted by the present inventor, when Fe ₂ O ₃ is contained in a small amount (preferably 1 to 10 ppm, particularly 2 to 5 ppm in mass), the total transmittance in the wavelength range of 400 to 750 nm is increased as a whole and the transmittance The transmittance at around 400 nm and at the wavelength of 750 nm can be increased by reducing the content of Cr ₂ O ₃ . Based on the above knowledge, the mass ratio Cr ₂ O ₃ / Fe ₂ O ₃ is preferably 0.01 to 0.13, 0.0125 to 0.1, 0.014 to 0.06, particularly 0.0167 to 0.0333. When the mass ratio Cr ₂ O ₃ / Fe ₂ O ₃ is out of the above range, the difference in transmittance between the maximum transmittance and the minimum transmittance in the wavelength range of 400 to 750 nm is likely to increase.

In order to reduce the content of Cr ₂ O ₃ and Fe ₂ O ₃ as much as possible, a high-purity glass raw material may be used, or a raw material combining equipment designed to prevent the mixture of Cr ₂ O ₃ and Fe ₂ O _{3 from} being mixed in the glass raw material. However, if Cr ₂ O ₃ and Fe ₂ O _{3 are} to be extremely reduced, a problem arises that the raw material cost and the production code are increased.

In the light guide plate of the present invention, it is preferable to reduce the contents of V ₂ O ₅ , NiO, MnO ₂ , Nd ₂ O ₃ , CeO ₂ and Er ₂ O ₃ in the glass plate as much as possible.

The content of V ₂ O _{5 in} the glass plate is preferably 0.03 mass% or less, 0.02 mass% or less, 0.015 mass% or less, 0.01 mass% or less, 0.005 mass% or less, particularly 0.003 mass% or less. If the content of V ₂ O ₅ is excessively large, the maximum transmittance at a wavelength of 400 to 750 nm and an optical path length of 100 mm is likely to decrease.

The content of NiO in the glass plate is preferably 0.03 mass% or less, 0.02 mass% or less, 0.015 mass% or less, 0.01 mass% or less, 0.005 mass% or less, particularly 0.003 mass% or less. When the content of NiO is too large, the maximum transmittance at an optical path length of 100 mm and a wavelength range of 400 to 750 nm is likely to decrease.

The content of MnO _{2 in} the glass plate is preferably 0.03 mass% or less, 0.02 mass% or less, 0.015 mass% or less, 0.01 mass% or less, 0.005 mass% or less, particularly 0.003 mass% or less. If the content of MnO ₂ is excessively large, the maximum transmittance at a wavelength of 400 to 750 nm and an optical path length of 100 mm are likely to be lowered.

The content of Nd ₂ O _{3 in} the glass plate is preferably 0.03 mass% or less, 0.02 mass% or less, 0.015 mass% or less, 0.01 mass% or less, 0.005 mass% or less, particularly 0.003 mass% or less. When the content of Nd ₂ O ₃ is excessively large, the maximum transmittance at a wavelength of 400 to 750 nm and an optical path length of 100 mm is likely to decrease.

The content of CeO _{2 in} the glass plate is preferably 0.03 mass% or less, 0.02 mass% or less, 0.015 mass% or less, 0.01 mass% or less, 0.005 mass% or less, particularly 0.003 mass% or less. If the content of CeO ₂ is excessively large, the maximum transmittance at a wavelength of 400 to 750 nm and an optical path length of 100 mm is likely to be lowered.

The content of Er ₂ O _{3 in} the glass plate is preferably 0.03 mass% or less, 0.02 mass% or less, 0.015 mass% or less, 0.01 mass% or less, 0.005 mass% or less, particularly 0.003 mass% or less. If the content of Er ₂ O ₃ is excessively large, the maximum transmittance at a wavelength of 400 to 750 nm and an optical path length of 100 mm is likely to decrease.

In the light guide plate of the present invention, the dimension of at least one side of the glass plate is preferably 1000 mm or more, 1500 mm or more, 2000 mm or more, 2500 mm or more, particularly 3000 mm or more. By doing so, the request for enlarging the display device can be satisfied.

The thermal expansion coefficient of the glass plate is preferably 120 × 10 ^-7 / ℃ or less, 95 × 10 ^-7 / ℃ or less, 70 × 10 ^-7 / ℃ or less, 60 × 10 ^-7 / ℃ or less, particularly 50 × 10 ^-7 / C or less. If the coefficient of thermal expansion is too high, the difference in dimensional change due to heat between the display panel and the light guide plate becomes large.

The glass plate preferably has a strain point of at least 460 DEG C, at least 480 DEG C, at least 500 DEG C, at least 520 DEG C, at least 530 DEG C, at least 550 DEG C and especially at least 590 DEG C. If the strain point is too low, the heat resistance of the glass plate tends to deteriorate. For example, when a reflective film, a diffusion film or the like is formed on the surface or end face of the glass plate at high temperature, the glass plate is likely to be thermally deformed. Here, the " strain point " is a value measured in accordance with JIS R3103.

The glass plate is composed of 40 to 80% of SiO ₂ , 1 to 15% of Al ₂ O ₃ , 0 to 20% of B ₂ O _3, 0 to 20% of Na ₂ O, 0 to 10% of MgO, 0 to 10% of CaO, 15%, SrO 0 to 15%, and BaO 0 to 35%. The reason why the content of each component is regulated as described above is shown below. In the description of the content range of each component, "%" means% by mass.

SiO ₂ is a component that becomes a network former of glass, and is a component that reduces thermal expansion coefficient and reduces dimensional change caused by heat. It is also a component that increases acid resistance and strain point. A suitable lower limit range of SiO ₂ is at least 40%, at least 60%, at least 65%, at least 67%, especially at least 70%, and a suitable upper limit range is at most 80%, at most 78%, at most 77% 73% or less. If the content of SiO ₂ increases, the high-temperature viscosity tends to be high, the melting property is lowered, and the cristobalite release agent tends to precipitate at the time of molding. On the other hand, as the content of SiO ₂ decreases, the thermal expansion coefficient tends to increase and the dimensional change due to heat tends to increase. Further, the acid resistance and the strain point are liable to be lowered.

Al ₂ O ₃ is a component that reduces the coefficient of thermal expansion and reduces dimensional changes due to heat. There is also an effect of increasing the strain point or suppressing the precipitation of cristobalite in molding. The suitable lower limit range of Al ₂ O ₃ is 1% or more, 2% or more, 5.5% or more, 7% or more, particularly 10% or more, and the suitable upper limit range is 15% or less. As the content of Al ₂ O ₃ increases, the liquidus temperature rises and it becomes difficult to form into a glass plate. On the other hand, when the content of Al ₂ O ₃ is decreased, the coefficient of thermal expansion increases and the dimensional change due to heat tends to increase. Further, the strain point is likely to be lowered.

B ₂ O ₃ is a component that acts as a flux and improves the meltability by lowering the high temperature viscosity. It is also a component that reduces the coefficient of thermal expansion and reduces dimensional changes due to heat. A suitable lower limit range of B ₂ O ₃ is at least 0%, at least 3%, at least 5%, at least 7%, at least 8%, especially at least 10% Or less. When the content of B ₂ O ₃ is increased, the strain point and the acid resistance tend to decrease. On the other hand, as the content of B ₂ O ₃ decreases, the thermal expansion coefficient tends to increase and the dimensional change due to heat tends to increase. Further, the meltability tends to decrease.

Na ₂ O is a component which improves the melting property by lowering the high temperature viscosity. A suitable lower limit range of Na ₂ O is at least 0%, at least 3%, at least 5%, at least 6%, at least 7%, especially at least 10%, a suitable upper limit range is at most 20%, at most 18% Especially 15% or less. As the content of Na ₂ O increases, the coefficient of thermal expansion increases and the dimensional change due to heat tends to increase. On the other hand, if the content of Na ₂ O is decreased, the meltability tends to be lowered.

MgO is a component which improves the melting property by lowering the high temperature viscosity. A suitable lower limit range of MgO is 0% or more, 0.05% or more, especially 0.1% or more, and a suitable upper limit range is 10% or less, 6% or less, 2% or less, 1% or less and especially 0.5% or less. If the content of MgO is excessively large, the silt is likely to precipitate at the time of molding.

CaO is a component which improves the melting property by lowering only the high-temperature viscosity without lowering the strain point. The suitable lower limit range of CaO is 0% or more, 0.5% or more, 1% or more, especially 2% or more, and the suitable upper limit range is 15% or less, 14% or less, 13% or less, 8% or less and especially 5% or less. If the content of CaO is excessively large, the silt is liable to precipitate at the time of molding.

SrO is a component that enhances chemical resistance and devitrification. A suitable lower limit range of SrO is 0% or more, 0.1% or more, especially 0.5% or more, and a suitable upper limit range is 15% or less, 10% or less, particularly 5% or less. When the content of SrO is increased, the density is increased, the thermal expansion coefficient is increased, and the dimensional change due to heat tends to increase. Further, the meltability tends to decrease.

BaO is a chemical that enhances chemical resistance and resistance. The suitable lower limit range of BaO is 0% or more, 0.1% or more, especially 0.5% or more, and the suitable upper limit range is 35% or less, 30% or less, 20% or less, especially 10% or less. When the content of BaO is increased, the density is increased or the thermal expansion coefficient is increased, and the dimensional change due to heat tends to increase. Further, the meltability tends to decrease.

A suitable lower limit of the amount of MgO and CaO is at least 0%, at least 0.1%, at least 0.5%, especially at least 1%, and a suitable upper limit range is at most 10%, at most 8%, at most 5%, at most 3% % Or less. If the total amount of MgO and CaO is too small, the meltability tends to decrease. On the other hand, if the total amount of MgO and CaO is excessively large, the coefficient of thermal expansion and the density are unreasonably high and the resistance to devitrification tends to decrease.

A suitable lower limit range of the total amount of SrO and BaO is 0% or more, 0.1% or more, 1% or more, 1.5% or more, especially 2% or more and a suitable upper limit range is 35% or less, 20% or less, % Or less. If the total amount of SrO and BaO is too small, the meltability tends to decrease. On the other hand, if the total amount of SrO and BaO is excessively large, the thermal expansion coefficient and density are unreasonably high and the resistance to devitrification tends to be lowered.

Suitable contents of Rh ₂ O ₃ , Cr ₂ O ₃ , Fe ₂ O ₃ , V ₂ O ₅ , NiO, MnO ₂ , Nd ₂ O ₃ , CeO ₂ and Er ₂ O ₃ are as described above.

Other components may be introduced in addition to the above components. For example, in order to lower the liquidus temperature, Y ₂ O ₃ , La ₂ O ₃ , Nb ₂ O ₅ and P ₂ O _{5 are added} to each 3%, and Li ₂ O, K ₂ O, Cs the ₂ O to each of 6%, may be introduced as a refining agent of _{as 2 O 3, Sb 2 O} 3, SnO 2, SO 3, F, Cl , etc. in total amount up to 2%. However, when As ₂ O ₃ and Sb ₂ O ₃ are environmental load substances and when a glass plate is formed by a float method, it is preferably reduced in the float bath to become a metal foreign substance, so that it is preferable to avoid substantial introduction, Are each less than 0.01%.

In the light guide plate of the present invention, it is preferable that the glass plate is formed by an overflow down-draw method. This makes it difficult to form a difference in temperature and composition on the front and back surfaces of the glass ribbon at the time of molding and to easily form a glass plate having a good surface quality in the unpolished state. As a result, it is possible to reduce the manufacturing cost of the light guide plate, It gets easier. This is because, in the case of the overflow down-draw method, the surface to be a surface is formed into a state of a free surface without contacting the grooved refractory.

In addition to the overflow down-draw method, a glass plate may be formed by a slot down-draw method, a float method, a roll-out method, a lead-down method, or the like. Further, in the float method, the temperature difference and the composition difference of the front and back surfaces of the glass ribbon are liable to occur at the time of molding, but when the temperature control during molding is strictly performed, the temperature difference and the compositional difference can be reduced.

The light guide plate of the present invention preferably has a dot shape printed on one surface (preferably a light output surface) of the glass plate, and the dot diameter of the dot shape gradually increases as it moves away from the end surface on which light from the light source is to be incident Is more preferable. This makes it easier to make the light emitted from the light output surface uniform in the plane. The dot shape can be formed by printing heat-resistant ink or glass frit on the surface of a glass plate, for example.

In the light guide plate of the present invention, the average surface roughness Ra of the end face of the glass plate (preferably the end face on which light from the light source should enter) is preferably 0.5 占 퐉 or less, 0.3 占 퐉 or less, 0.2 占 퐉 or less, . This makes it easier to reduce the optical loss when the light from the light source enters the end face. In addition, a high-quality reflective layer can be easily formed on the end face.

For example, if the end surface of the glass plate is polished with a # 2000 grindstone, the average surface roughness Ra of the end surface of the glass plate can be reduced as much as possible. In addition, when the end face of the glass plate is etched, the average surface roughness Ra of the end face of the glass plate can be reduced without causing polishing scratches.

It is preferable that the end face of the glass plate does not have a chamfered portion. This makes it easier to introduce the light from the light source into the inside of the glass plate.

It is preferable that the light guide plate of the present invention has a reflective layer formed on all or a part of the end surface other than the end surface on which the light from the light source should enter and a reflective layer is formed on all of the end surfaces other than the end surface on which light from the light source should enter Is particularly preferable. This makes it difficult for the light propagated inside the glass plate to leak from the end face. Further, the reflection film may be formed directly on the end face as the reflection layer, but a reflection seal may be attached to the end face.

In the light guide plate of the present invention, a diffusion plate may be attached to the light exit surface to diffuse the light emitted from the light exit surface, or a diffusion layer may be formed on the light exit surface.

The light guide plate of the present invention can also be utilized as a substrate of a display panel in which the function of the light guide plate is performed in parallel. By doing so, it is possible to simplify the constitution of members of the display device.

The glass plate of the present invention is characterized by having a transmittance of 93% or more at an optical path length of 500 mm and a wavelength range of 400 to 750 nm. The glass plate of the present invention is characterized in that the difference in transmittance between the maximum transmittance and the minimum transmittance in a wavelength range of 400 to 750 nm is 6% or less. Since the technical features of the glass plate of the present invention are already described in the description of the light guide plate of the present invention, detailed description thereof is omitted here.

In the glass plate of the present invention, the transmittance at the optical path length of 0.15 mm and the wavelength of 250 nm is preferably at least 85%, at least 88%, at least 90%, at least 92%, at least 94% Or more. If the transmittance at an optical path length of 0.15 mm and a wavelength of 250 nm is too low, it becomes difficult to develop a use requiring sterilization and live viruses.

Example 1

Hereinafter, the present invention will be described on the basis of examples. However, the following embodiments are merely examples. The present invention is not limited to the following embodiments.

Table 1 shows Examples (Sample Nos. 1 to 4) of the present invention.

First, a glass batch obtained by combining glass raw materials so as to have a glass composition in the tables was placed in a platinum crucible and then melted at 1200 to 1450 占 폚 for 24 hours. In the melting of the glass batch, homogenization was performed by stirring using a platinum stirrer. Subsequently, the molten glass was poured on a carbon plate to form a plate, and then the mixture was allowed to stand for 30 minutes at a temperature near the standing point. The thermal expansion coefficient CTE, the strain point Ps, the maximum transmittance and the minimum transmittance in the wavelength range of 400 to 700 nm were evaluated for each of the obtained samples in the temperature range of 30 to 380 ° C.

The coefficient of thermal expansion CTE in the temperature range of 30 to 380 ° C is a value obtained by measuring the average thermal expansion coefficient at 30 to 380 ° C in accordance with JIS R3102 using a dilatometer. The strain point is a value measured in accordance with JIS R3103.

The maximum transmittance and the minimum transmittance are values measured by UV-3100PC manufactured by Shimadzu Corporation.

From the above results, it can be seen that the samples Nos. 1 to 4 have high heat resistance because they have high strain points and have a lower coefficient of thermal expansion than the resin plate, so that dimensional changes are hardly caused by temperature rise, and also the maximum transmittance at wavelengths of 400 to 750 nm The difference in transmittance between minimum transmittance and transmittance is small. Therefore, it is considered that the samples Nos. 1 to 4 are suitable as a light guide plate, particularly a light guide plate for use in an edge light type surface light emitting device.

Example 2

First, a glass raw material was prepared so that the glass composition contained 69% SiO ₂ , 5.8% Al ₂ O ₃ , 10.2% B ₂ O ₃ , 3.1% CaO, 10.7% Na ₂ O, 0.9% ZnO and 20.3% And then melted in a continuous melting furnace to obtain a molten glass. Subsequently, the obtained molten glass was formed into a plate shape by an overflow down-draw method, and then cooled. The glass plate was cut into a predetermined size and the surface roughness Ra of the end face was 0.3 μm. Here, in the production of the glass plate, a glass raw material such as Fe ₂ O ₃ was used as a glass raw material so that the content of Rh ₂ O ₃ was less than 0.2 ppm, the content of Fe ₂ O ₃ was 5 ppm and the content of Cr ₂ O ₃ was less than 0.1 ppm ₃ , and a glass manufacturing facility designed to prevent coloring components such as Rh ₂ O ₃ from being mixed into glass from the glass plate manufacturing facility was used.

The obtained glass plate was measured for the transmittance at an optical path length of 150 mm and a wavelength range of 400 to 750 nm using UH4150 manufactured by Hitachi High-Tech Science Corporation, and converted into an internal transmittance having an optical path length of 500 mm. As a result, Mm, the maximum transmittance in the wavelength range of 400 to 750 nm was 99%, and the difference in transmittance between the maximum transmittance and the minimum transmittance in the wavelength range of 400 to 750 nm was 3%. 3 shows the transmittance curve at an optical path length of 500 mm and a wavelength range of 400 to 750 nm.

Further, a result of measuring the coefficient of thermal expansion CTE in the temperature range of 30 ~ 380 ℃ by the above method with respect to the resultant glass plate, and 66.3 × 10 ^-7 / ℃, was a result of measuring the transformation point, 536 ℃.

From the above results, it is considered that the light guide plate having this glass plate is hardly changed in dimension as the temperature rises, and the luminance characteristic of the display device can be increased.

Example 3

First, glass raw materials were combined so as to contain 69% of SiO ₂ , 5.8% of Al ₂ O ₃ , 10.2% of B ₂ O ₃ , 3.1% of CaO, 10.7% of Na ₂ O, 0.9% of ZnO and 20.3% of SnO as mass% , And the mixture was melted in a continuous melting furnace to obtain a molten glass. Subsequently, the obtained molten glass was formed into a plate shape of 0.15 mm in thickness by the overflow down-draw method, and then cooled to a predetermined size, and the surface roughness Ra of the end face was 0.3 μm to obtain a glass plate. Here, as the glass raw material is less than the content of Rh ₂ O ₃ in the glass sheet 0.2ppm in the production of a glass plate, with a content of Fe ₂ O ₃ mass content of 4ppm, Cr ₂ O ₃ is less than 0.1ppm Fe ₂ O ₃ , and a glass manufacturing facility designed to prevent coloring components such as Rh ₂ O ₃ from being mixed into glass from the glass plate manufacturing facility was used.

The obtained glass plate was measured for transmittance at a plate thickness of 0.15 mm (optical path length of 0.15 mm) and a wavelength range of 200 to 700 nm using Hitachi High-Tech Science Corporation U-4100, and then converted into an internal transmittance. Fig. 4 shows data showing the transmittance curve (internal transmittance curve) at a wavelength range of 200 to 700 nm of this sample, and Fig. 5 shows data showing an external transmittance curve at a wavelength range of 200 to 750 nm. 4 and 5, the transmittance (internal transmittance) of the sample was 250% at a wavelength of 250 nm and the external transmittance was 88%.

With respect to this glass sample, the coefficient of thermal expansion CTE in the temperature range of 30 to 380 占 폚 was measured by the above-mentioned method and found to be 66.3 占 10 ^-7 / 占 폚.

In view of the above, this glass sample is well suited for applications requiring sterilization and dead virus because it penetrates deep ultraviolet rays well. Also, since it has higher thermal expansion coefficient than quartz glass, it is excellent in sealing and sealing properties of ceramics and metals.

(Industrial availability)

The glass plate of the present invention is suitable for applications requiring a high transmittance in addition to the light guide plate. For example, a glass substrate for a display, a glass substrate for an optical communication device, a glass substrate for a semiconductor manufacturing process, or the like. Further, since the glass plate of the present invention has a high transmittance in the outer core region and a high thermal expansion coefficient even in quartz glass, it can be developed into a wide range of fields such as medical treatment, analysis, environment, agriculture and the like. Further, since the glass according to the present invention has a high transmittance in the ultraviolet region, it can be processed into a tubular shape and suitably used as a sterilizing lamp.

1: edge light type surface emitting device 2, 12: light source
3, 10: light guide plate 4, 19: reflective layer
5: diffusion plate 6: light reflection surface
7: light emitting surface 11: glass plate
13, 16, 17, 18: end face 14: rear face
15: Dot shape

Claims (17)

And the difference in transmittance between the maximum transmittance and the minimum transmittance in a wavelength range of 400 to 750 nm is 12% or less in the optical path length of 100 mm and the glass plate has a content of Rh ₂ O ₃ in mass of less than 1 ppm . The method according to claim 1,
Wherein the content of Fe ₂ O _{3 in} the glass plate is less than 50 ppm by mass and the maximum transmittance of the glass plate at an optical path length of 100 mm and a wavelength range of 400 to 750 nm is 85% or more. 3. The method according to claim 1 or 2,
Wherein a content of Cr ₂ O _{3 in} the glass plate is 5 ppm or less in mass. 4. The method according to any one of claims 1 to 3,
Wherein a dot shape is printed on one surface of the glass plate. 5. The method of claim 4,
Wherein the dot-shaped dot diameter gradually increases as the light from the light source is separated from the end surface on which light should be incident. 6. The method according to any one of claims 1 to 5,
Wherein an average surface roughness Ra of an end face of the glass plate is 0.5 占 퐉 or less. 7. The method according to any one of claims 1 to 6,
Wherein a reflective layer is formed on all or a part of the end surface other than the end surface on which light from the light source should be incident. 8. The method according to any one of claims 1 to 7,
Wherein the glass plate contains 40 to 80% of SiO ₂ , 1 to 15% of Al ₂ O ₃ , 0 to 20% of B ₂ O _3, 0 to 20% of Na ₂ O, 0 to 10% of MgO, 15%, SrO 0 - 15%, and BaO 0 - 35%. 9. The method according to any one of claims 1 to 8,
Wherein the glass plate has a thermal expansion coefficient of 120 x 10 < ^-7 > / DEG C or less. 10. The method according to any one of claims 1 to 9,
A light guide plate characterized by being used for an edge light type surface light emitting device. Wherein the maximum transmittance at an optical path length of 500 mm and a wavelength range of 400 to 750 nm is 93% or more. 12. The method of claim 11,
Wherein a content of Rh ₂ O ₃ is less than 1 ppm by mass and a content of Fe ₂ O ₃ is 10 ppm or less by mass. Wherein the difference in transmittance between the maximum transmittance and the minimum transmittance in a wavelength range of 400 to 750 nm is 6% or less. 14. The method of claim 13,
Wherein the glass composition contains Cr ₂ O ₃ and Fe ₂ O ₃ , and the content of Cr ₂ O ₃ / Fe ₂ O ₃ is 0.01 to 0.13. The method according to claim 13 or 14,
Wherein the content of Fe ₂ O _{3 in} the glass composition is 1 to 10 ppm by mass. 16. The method according to any one of claims 13 to 15,
Wherein the maximum transmittance at an optical path length of 500 mm and a wavelength range of 400 to 750 nm is 93% or more. 17. The method according to any one of claims 11 to 16,
Wherein the optical path length is 0.15 mm and the transmittance at a wavelength of 250 nm is 85% or more.

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