TWI698405B - Light guide plate and glass plate - Google Patents

Abstract

The light guide plate of the present invention is characterized by having 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 optical path length of the glass plate is 100 mm, and the wavelength range is 400 nm to 750 nm The difference in transmittance between the maximum transmittance and the minimum transmittance in is 12% or less.

Description

Light guide plate and glass plate

The present invention relates to a light guide plate, in particular to a light guide plate suitable for edge light type surface light emitting devices.

Since the past, liquid crystal display devices have been used in liquid crystal televisions and 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 light emitting device, for example, a direct type and an edge light type are known.

In the direct type surface light emitting device, the light source is arranged on the back surface opposite to the light exit surface. When a point light source such as a light emitting diode (Light Emitting Diode) is used as a light source, multiple LED chips are required to compensate for the brightness, and the unevenness of the brightness characteristics becomes very large.

Therefore, the current edge light type surface light emitting device is becoming the mainstream. The edge light type surface light-emitting device is equipped with a light source such as an LED, a light guide plate, and a reflective layer such as a reflective film. The light source is arranged on an end surface in a direction orthogonal to the light exit surface (surface). The light guide plate is configured to take in the light from the light source from the end surface and transmit it to the inside by total reflection, and to emit it in a planar shape from the light exit surface. As the light guide plate, a resin plate such as acrylic resin is generally used (see Patent Document 1 to Patent Document 4). The reflective layer is arranged on the back side facing the light emission surface, and is arranged to reflect light that has penetrated to the back surface and to cause a display surface such as a liquid crystal panel to emit light. Furthermore, in order to make the display surface of a liquid crystal panel etc. emit light uniformly, a diffusion layer may be arrange|positioned on the light-exit surface side of a light guide plate.

FIG. 1 is a conceptual cross-sectional view showing an example of an edge light type surface light-emitting device 1. The edge light type surface light emitting device 1 includes a light source such as an LED, a light guide plate 3, a reflective layer 4, and a diffusion layer 5. The light from the light source 2 enters from the end surface of the light guide plate 3 and propagates to the inside of the light guide plate 3. The light reaching the light reflection surface 6 is reflected by the reflection layer 4, and then travels toward the light exit surface 7, and is diffused by the diffusion layer 5. As a result, the display surface of the liquid crystal panel or the like arranged above the diffusion layer 5 can be made to emit light uniformly. In addition, a reflection layer may be formed on the end surface of the light guide plate 3 on the opposite side to the end surface of the light guide plate 3 where the light from the light source 2 is incident. [Prior Art Document] [Patent Document]

Patent Document 1: Japanese Patent Laid-Open No. 2012-123933 Patent Document 2: Japanese Patent Laid-Open No. 2012-138345 Patent Document 3: Japanese Patent Laid-Open No. 2012-216523 Patent Document 4: Japanese Patent Laid-Open No. 2012-216528 Bulletin

In the edge light type surface light emitting device, if light is generated from the light source, heat is generated, and the temperature of the light guide plate also rises with this. Moreover, when a resin plate is used as the light guide plate, the dimensional change of the light guide plate caused by heat becomes larger than that of the liquid crystal panel. The reason is that the thermal expansion coefficient of the resin plate is high. For example, the thermal expansion coefficient of an acrylic resin board is about 700×10 ^-7 /°C. Therefore, until now, a gap is provided in the frame portion of the liquid crystal display device to correct the dimensional change of the light guide plate, so that undue stress will not be generated due to the difference in the dimensional change.

However, in recent years, due to the narrowing of the frame of the liquid crystal display device, it is difficult to correct the dimensional change of the light guide plate by the frame portion of the liquid crystal display device.

In addition, in the case of using a resin plate as the light guide plate, when the light from the light source enters from the end surface and penetrates to the light exit surface, the amount of light is weakened. As a result, the brightness characteristics of the display device are easily degraded.

Therefore, the present invention was made in view of the above-mentioned circumstances, and its technical problem is to invent a light guide plate in which dimensional changes are difficult to occur as the temperature rises, and it is difficult to reduce the brightness characteristics of a display device.

As a result of diligent research, the inventors found that by selecting a glass plate with a small dimensional change caused by temperature changes as the light guide plate, and reducing the content of Rh ₂ O ₃ in the glass plate, the transmittance of the glass plate is limited to By specifying the range, the technical problem can be solved and proposed as the present invention. That is, the light guide plate of the present invention is characterized by having 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 optical path length of the glass plate is 100 mm and the wavelength range of 400 nm to 750 nm The difference between the maximum transmittance and the minimum transmittance is 12% or less. Here, the "maximum transmittance and minimum transmittance in the optical path length of 100mm and the wavelength range of 400nm to 750nm" can be measured with a commercially available transmittance measuring device, for example, UV-3100PC manufactured by Shimadzu Corporation To determine. Furthermore, as long as there is no special indication, the "transmittance" refers to the internal transmittance calculated by Equation 1.

[Number 1] logT _in =log(I ₁ /I ₀ )-logR logT _in : Internal transmittance (%) I ₀ : The intensity of incident light (%) I ₁ : The amount of light passing through a specific optical path length Intensity (%) R: Attenuation rate of light caused by 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, if a glass plate is selected as the light guide plate, the difference in dimensional changes between the display panel and the light guide plate becomes small, and it is possible to appropriately cope with the narrowing of the frame of a display device such as a liquid crystal display device.

The inventors found that if the difference in transmittance of the glass plate in the visible region is small, the brightness characteristics of the display device are improved. Furthermore, the present inventors found that Rh ₂ O ₃ in the glass plate has a great influence on the absorption near the wavelength of 450 nm, and if 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 limited to less than 1 ppm by mass, and the optical path length of the glass plate is 100 mm and the wavelength range is 400 nm～750. The difference between the maximum transmittance and the minimum transmittance in nm is limited to 12% or less, which significantly improves the brightness characteristics of the display device.

Second, the light guide plate of the present invention is preferably that the content of Fe ₂ O ₃ in the glass plate is less than 50 ppm by mass, and the glass plate has the maximum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm The rate is over 85%. If the Fe ₂ O ₃ content in the glass plate is reduced, the maximum transmittance of the glass plate in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm can be increased. Fe ₂ O ₃ exists in the state of Fe ^{3 +} or Fe ^{2 +} in the glass. Fe ^{3 +} has an absorption peak near a wavelength of 380 nm, and lowers the transmittance in the ultraviolet region and the visible region on the short wavelength side. Fe ^{2 +} has an absorption peak near the wavelength of 1080 nm, and lowers the transmittance in the visible region on the long wavelength side. Therefore, if the content of Fe ₂ O ₃ increases, the maximum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm is likely to decrease. Generally, a large amount of Fe ₂ O ₃ is mixed into the glass sheet from the glass raw material or the manufacturing process. Therefore, since the conventional glass plate has a large Fe ₂ O ₃ content, it is difficult to improve the brightness characteristics of the display device. Therefore, if the content of Fe ₂ O ₃ in the glass plate is limited to less than 50 ppm by mass, the brightness characteristics of the display device can be improved. Furthermore, the "Fe ₂ O ₃ "in the present invention includes divalent iron oxide and trivalent iron oxide, and the divalent iron oxide is converted into Fe ₂ O ₃ for processing. Regarding other oxides, the same applies to the stated oxides.

Third, the light guide plate of the present invention preferably has a content of Cr ₂ O ₃ in the glass plate of 5 ppm or less by mass. According to the investigation of the present inventors, Cr ₂ O ₃ in the glass plate has a large influence on the absorption near the wavelength of 630 nm. If its 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 is preferably printed with a dot pattern on one surface (preferably the light exit surface) of the glass plate. If so, it is easy to uniformize the light emitted from the light exit surface in the surface.

Fifth, in the light guide plate of the present invention, it is preferable that the diameter of the dots of the dot pattern gradually increases as the distance from the end surface where the light from the light source should be incident. If so, it is easy to uniformize the light emitted from the light exit surface in the surface.

Sixth, the light guide plate of the present invention preferably has an end surface of the glass plate (preferably an end surface where light from a light source should be incident) with an average surface roughness Ra of 0.5 μm or less. If so, when the light from the light source enters the end surface, it is easy to reduce the light loss.

Seventh, the light guide plate of the present invention preferably has a reflective layer formed on all or a part of the end surface other than the end surface where light from the light source should enter. If so, the light propagating to the inside of the glass plate will hardly leak from the end surface.

Fig. 2 is a conceptual perspective view showing an example of the light guide plate of the present invention. As shown in FIG. 2, the light guide plate 10 includes a glass plate 11. The light from the light source 12 enters from the end surface 13 of the glass plate 11, propagates to the inside of the glass plate 11, and exits from the light exit surface. Here, the content of Rh ₂ O ₃ in the glass plate 11 is less than 1 ppm by mass, and the glass plate 11 has a maximum transmittance and a minimum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm. The transmittance difference is less than 12%. In addition, a dot pattern 15 is formed on the back surface 14 of the glass plate 11 facing the light emission surface. In addition, the diameter of the dots of the dot pattern 15 gradually increases from the end surface 13 to the end surface 16. With this dot pattern 15, the light emitted from the light emitting surface is uniformized in the surface. Furthermore, a reflection layer 19 is formed on the end surface 16, the end surface 17, and the end surface 18 of the glass plate, respectively. Then, the light reaching the end surface 16, the end surface 17, and the end surface 18 of the glass plate is reflected by the reflective layer 19, returns to the inside of the glass plate 11, and finally exits from the light exit surface.

In addition, a plurality of glass plates 11 of the present invention may be joined and used. For example, two glass plates 11 are prepared. No reflective layer is formed on the end surface 17 of one of the glass plate 11, and no reflective layer is formed on the end surface 18 of the other glass plate 11. The end faces are joined by a transparent adhesive with the same refractive index, thereby making a large-area light guide plate.

Eighth, the light guide plate of the present invention is preferably a glass plate, based on mass%, containing 40% to 80% of SiO ₂ , 1% to 15% of Al ₂ O ₃ , and 0 to 20% of B ₂ O ₃ , 0 -20% Na ₂ O, 0-10% MgO, 0-15% CaO, 0-15% SrO, 0-35% BaO as the glass composition. If so, the thermal expansion coefficient of the glass plate tends to decrease.

Ninth, the light guide plate of the present invention is preferably a glass plate with a thermal expansion coefficient of 120×10 ^-7 /°C or less. Here, the "coefficient of thermal expansion" refers to a value obtained by measuring the average coefficient of thermal expansion at 30°C to 380°C in accordance with JIS R3102 using a dilatometer.

Tenth, the light guide plate of the present invention is preferably used in edge light type surface light emitting devices.

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

Twelfth, in the glass plate of the present invention, it is preferable that the content of Rh ₂ O ₃ is less than 1 ppm by mass, and the content of Fe ₂ O ₃ is less than 10 ppm by mass.

Thirteenth, the glass plate of the present invention is characterized in that the difference between the maximum transmittance and the minimum transmittance in the wavelength range of 400 nm to 750 nm is 6% or less.

Fourteenth, the glass plate of the present invention preferably contains Cr ₂ O ₃ and Fe ₂ O ₃ in the glass composition, and the mass ratio Cr ₂ O ₃ /Fe ₂ O ₃ is 0.01 to 0.13. If the mass ratio Cr ₂ O ₃ /Fe ₂ O _{3 is} restricted to the above range, the difference between the maximum transmittance and the minimum transmittance in the wavelength range of 400 nm to 750 nm can be reduced as much as possible.

Fifteenth, the glass plate of the present invention preferably has a Fe ₂ O ₃ content of 1 ppm to 10 ppm by mass in the glass composition.

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

Seventeenth, the glass plate of the present invention preferably has a transmittance of 85% or more in an optical path length of 0.15 mm and a wavelength of 250 nm.

In the light guide plate of the present invention, the difference between the maximum transmittance and the minimum transmittance of the glass plate in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm is preferably 12% or less, 10% or less, 8% Or less, 6% or less, 5% or less, especially 4% or less. If the difference in transmittance is too large, the brightness characteristics of the display device are likely to decrease.

The maximum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm is preferably 88% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, More than 96%, more than 97%, more than 98%, especially more than 99%. If the maximum transmittance is too low, the brightness characteristics of the display device are likely to decrease.

The maximum transmittance in the optical path length of 200 mm and the wavelength range of 400 nm to 750 nm is preferably 86% or more, 88% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, Above 95%, above 96%, above 97%, above 98%, especially above 99%. If the maximum transmittance is too low, the brightness characteristics of the display device are likely to decrease.

The maximum transmittance in the optical path length of 500 mm and the wavelength range of 400 nm to 750 nm is preferably 85% or more, 86% or more, 88% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, especially 99% or more. If the maximum transmittance is too low, the brightness characteristics of the display device are likely to decrease.

In the light guide plate of the present invention, the maximum transmittance of the glass plate in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm is 85% or more, preferably 87%, 88%, or 89%, especially Is more than 90%. If the maximum transmittance is too low, the brightness characteristics of the display device are likely to decrease.

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 ppm to 0.5 ppm, 0.05 ppm to 0.4 ppm, especially 0.1 ppm to 0.3 ppm. If the content of Rh ₂ O ₃ is too large, the transmittance difference between the maximum transmittance and the minimum transmittance in the wavelength range of 400 nm to 750 nm is likely to become too large. Furthermore, if the content of Rh ₂ O ₃ is too small, it is difficult to use a high-strength Pt-Rh alloy in glass manufacturing equipment, and the manufacturing cost of the glass plate increases.

In order to reduce the content of Rh ₂ O ₃ as much as possible, it is enough to use high-purity glass raw materials, or adjust the glass manufacturing conditions so that Rh ₂ O ₃ is not mixed, or reduce the use of Pt-Rh alloy in glass manufacturing equipment. .

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 ppm to 1.5 ppm, 0.2 ppm to 1 ppm, especially 0.3 ppm to 0.8 ppm by mass. If the content of Cr ₂ O ₃ is too large, the transmittance difference between the maximum transmittance and the minimum transmittance in the wavelength range of 400 nm to 750 nm is likely to become too large. Furthermore, if the content of Cr ₂ O ₃ is too small, the cost of raw materials and the manufacturing cost of the glass plate increase.

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 by mass. ppm or less, 12 ppm or less, 10 ppm or less, 8 ppm or less, 6 ppm or less, especially 1 ppm to 5 ppm. If the content of Fe ₂ O ₃ is too large, the maximum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm is likely to decrease. Furthermore, if the content of Fe ₂ O ₃ is less than 1 ppm by mass, it is difficult to reduce the transmittance difference between the maximum transmittance and the minimum transmittance in the wavelength range of 400 nm to 750 nm.

In the wavelength range of 400 nm to 750 nm, the transmittance around the wavelength of 550 nm is relatively easy to increase, and the transmittance around the wavelength of 400 nm and around the wavelength of 750 nm is relatively easy to decrease. Therefore, if the transmittance near the wavelength of 550 nm is slightly decreased, while the transmittance near the wavelength of 400 nm and the wavelength of 750 nm are increased, the maximum transmittance and the transmittance in the wavelength range of 400 nm to 750 nm can be reduced as much as possible. The transmittance difference of the minimum transmittance. According to the investigation of the present inventors, if Fe ₂ O _{3 is} contained in a small amount (preferably 1 ppm to 10 ppm by mass, especially 2 ppm to 5 ppm), the entire wavelength range of 400 nm to 750 nm can be increased. At the same time, the overall transmittance in 550 nm is slightly reduced. Furthermore, if the content of Cr ₂ O ₃ is reduced, the transmittance in the vicinity of 400 nm and 750 nm can be increased. According to the above findings, 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, and particularly 0.0167 to 0.0333. If the mass ratio Cr ₂ O ₃ /Fe ₂ O ₃ is outside the above-mentioned range, the transmittance difference between the maximum transmittance and the minimum transmittance in the wavelength range of 400 nm 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, only use high-purity glass raw materials, or use raw material blending equipment designed so that Cr ₂ O ₃ and Fe ₂ O _{3 are} not mixed into the glass raw materials. can. However, if Cr ₂ O ₃ and Fe ₂ O ₃ are to be extremely reduced, the problem of rising raw material costs or production costs will arise.

In the light guide plate of the present invention, it is preferable to reduce the content 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, and particularly 0.003 mass% or less. If the content of V ₂ O ₅ is too large, the maximum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm 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, and particularly 0.003 mass% or less. If the content of NiO is too large, the maximum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm is likely to decrease.

The content of MnO ₂ in the glass plate is preferably 0.03% by mass or less, 0.02% by mass or less, 0.015% by mass or less, 0.01% by mass or less, 0.005% by mass or less, particularly 0.003% by mass or less. If the content of MnO ₂ is too large, the maximum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm is likely to decrease.

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, especially 0.003 mass% or less. If the content of Nd ₂ O ₃ is too large, the maximum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm 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, and particularly 0.003 mass% or less. If the content of CeO ₂ is too large, the maximum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm is likely to decrease.

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, especially 0.003 mass% or less. If the content of Er ₂ O ₃ is too large, the maximum transmittance in the optical path length of 100 mm and the wavelength range of 400 nm to 750 nm is likely to decrease.

In the light guide plate of the present invention, the size 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, especially 3000 mm or more. If this is the case, it is possible to meet the requirements for increasing the size of the display device.

Thermal expansion coefficient of the glass sheet is preferably 120 × 10 ^-7 / ℃ less, 95 × 10 ^-7 / ℃ less, 70 × 10 ^-7 / ℃ less, 60 × 10 ^-7 / ℃ or less, in particular 50 × 10 ^- Below ⁷ /℃. If the coefficient of thermal expansion is too high, the difference in dimensional changes caused by heat between the display panel and the light guide plate will increase.

The strain point of the glass plate is preferably 460°C or higher, 480°C or higher, 500°C or higher, 520°C or higher, 530°C or higher, 550°C or higher, especially 590°C or higher. If the strain point is too low, the heat resistance of the glass plate is likely to decrease. For example, if a reflective film, a diffusion film, etc. are formed on the surface or end face of the glass plate at high temperature, the glass plate is likely to be thermally deformed. Here, "strain point" refers to a value measured in accordance with JIS R3103.

The glass plate is preferably based on mass %, containing 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, 0-10% MgO, 0-15% CaO, 0-15% SrO, 0-35% BaO are used as glass composition. The reasons for limiting the content of each component as described above are shown below. In addition, in the description of the content range of each component, the expression% means mass %.

SiO ₂ is a component that becomes a network former of glass, and is a component that lowers the coefficient of thermal expansion and reduces dimensional changes caused by heat. In addition, it is a component that improves acid resistance and strain point. The suitable lower limit range of SiO ₂ is 40% or more, 60% or more, 65% or more, 67% or more, especially 70% or more, and the suitable upper limit range is 80% or less, 78% or less, 77% or less, 75% or less , Especially below 73%. When the content of SiO ₂ increases, the high-temperature viscosity increases, the meltability decreases, and devitrification products of cristobalite are likely to precipitate during molding. On the other hand, when the content of SiO ₂ decreases, the coefficient of thermal expansion increases and the dimensional change due to heat tends to increase. In addition, acid resistance and strain point tend to drop.

Al ₂ O ₃ is a component that lowers the thermal expansion coefficient and reduces dimensional changes caused by heat. In addition, it also has the effect of increasing the strain point or suppressing the precipitation of devitrification products of cristobalite during 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, especially 10% or more, and the suitable upper limit range is 15% or less, 13% or less, especially 12% or less . When the content of Al ₂ O ₃ increases, the liquidus temperature rises, making it difficult to form into a glass sheet. On the other hand, when the content of Al ₂ O ₃ decreases, the coefficient of thermal expansion increases and the dimensional change due to heat tends to increase. In addition, the strain point tends to drop.

B ₂ O ₃ is a component that functions as a flux, reduces high-temperature viscosity, and improves meltability. In addition, it is a component that lowers the thermal expansion coefficient and reduces the dimensional change caused by heat. The suitable lower limit range of B ₂ O ₃ is 0% or more, 3% or more, 5% or more, 7% or more, 8% or more, especially 10% or more, and the suitable upper limit range is 15% or less, 13% or less, especially Less than 12%. When the content of B ₂ O ₃ increases, the strain point and acid resistance tend to decrease. On the other hand, when the content of B ₂ O ₃ decreases, the coefficient of thermal expansion increases and the dimensional change due to heat tends to increase. In addition, meltability tends to decrease.

Na ₂ O is a component that reduces high-temperature viscosity and improves meltability. The suitable lower limit range of Na ₂ O is 0% or more, 3% or more, 5% or more, 6% or more, 7% or more, especially 10% or more, and the suitable upper limit range is 20% or less, 18% or less, 16% Below, 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 decreases, the meltability tends to decrease.

MgO is a component that reduces high-temperature viscosity and improves meltability. The suitable lower limit range of MgO is 0% or more, 0.05% or more, especially 0.1% or more, and the suitable upper limit range is 10% or less, 6% or less, 2% or less, 1% or less, especially 0.5% or less. If the content of MgO is too large, devitrified materials are likely to precipitate during molding.

CaO is a component that does not lower the strain point but only lowers the high-temperature viscosity and improves the meltability. 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, especially 5% the following. If the content of CaO is too large, devitrified materials are likely to precipitate during molding.

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

BaO is a component that improves chemical resistance and devitrification 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 increases, the density increases, or the thermal expansion coefficient increases, and the dimensional change due to heat tends to increase. In addition, meltability tends to decrease.

The suitable lower limit range of the total amount of MgO and CaO is 0% or more, 0.1% or more, 0.5% or more, especially 1% or more, and the suitable upper limit range is 10% or less, 8% or less, 5% or less, and 3% or less , Especially below 2%. If the total amount of MgO and CaO is too small, the meltability is likely to decrease. On the other hand, if the total amount of MgO and CaO is too large, the coefficient of thermal expansion and density become inappropriately high, and the devitrification resistance tends to decrease.

The 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 the suitable upper limit range is 35% or less, 20% or less, and 10% or less , Especially 5% or less. If the total amount of SrO and BaO is too small, the meltability is likely to decrease. On the other hand, if the total amount of SrO and BaO is too large, the coefficient of thermal expansion and density become inappropriately high, and the devitrification resistance tends to decrease.

The appropriate 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.

In addition to the aforementioned components, other components may also be introduced. 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 may be introduced up to 3% each, and up to 6% each may be introduced to lower the melting temperature. As for Li ₂ O, K ₂ O, and Cs ₂ O, it is also possible to introduce As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , F, Cl, etc. as fining agents up to 2% in total. However, As ₂ O ₃ and Sb ₂ O ₃ are environmentally hazardous substances. In addition, when the glass plate is formed by the float method, it is reduced in the floating bath and becomes a metal foreign substance. Therefore, it is better to avoid substantial Introducing, specifically, it is preferable to set the content to less than 0.01%.

In the light guide plate of the present invention, the glass plate is preferably formed by an overflow down-draw method. If so, it is difficult to produce a temperature difference between the front and back of the glass ribbon and a difference in composition during molding, and it is easy to mold a glass plate with good surface quality without polishing. As a result, it is easy to reduce the manufacturing cost of the light guide plate. The uniformity of brightness characteristics. The reason is that in the case of the overflow down-draw method, the surface that should be the surface is not in contact with the water-conducting tubular refractory, but is formed in the state of a free surface.

Furthermore, in addition to the overflow down-draw method, the glass plate may also be formed by a slot down draw method, a float method, a roll out method, a redraw method, and the like. Furthermore, in the float method, the temperature difference and composition difference between the front and back surfaces of the glass ribbon are likely to occur during molding, but if the temperature control during molding is strictly performed, the temperature difference and composition difference can be reduced.

The light guide plate of the present invention is preferably printed with a dot pattern on one surface (preferably the light exit surface) of the glass plate. It is more preferable that the diameter of the dot of the dot pattern gradually becomes larger as it moves away from the end surface where the light from the light source should be incident. If so, it is easy to uniformize the light emitted from the light exit surface in the surface. Furthermore, the dot pattern can be formed, for example, by printing heat-resistant ink or glass frit on the surface of a glass plate.

In the light guide plate of the present invention, the average surface roughness Ra of the end surface of the glass plate (preferably the end surface where light from the light source should be incident) is preferably 0.5 μm or less, 0.3 μm or less, 0.2 μm or less, especially 0.1 μm the following. If so, when the light from the light source enters the end surface, it is easy to reduce the light loss. In addition, it is easy to form a high-quality reflective layer on the end surface.

For example, if the end surface of a glass plate is polished with a #2000 grinding stone, the average surface roughness Ra of the end surface of the glass plate can be reduced as much as possible. In addition, if the end surface of the glass plate is etched, the average surface roughness Ra of the end surface of the glass plate can be reduced without causing grinding damage.

The end surface of the glass plate preferably does not have a chamfered portion. If so, it is easy to take in the light from the light source into the glass plate.

The light guide plate of the present invention preferably has a reflective layer formed on all or part of the end face other than the end face where light from the light source should be incident, and it is particularly preferred that the reflective layer is formed on all the end faces other than the end face where light from the light source should be incident. . If so, the light propagating to the inside of the glass plate will hardly leak from the end surface. Furthermore, as the reflective layer, a reflective film can be formed directly on the end surface, or a reflective sealing material can be attached to the end surface.

In order to diffuse the light emitted from the light exit surface of the light guide plate of the present invention, a diffusion plate may be attached to 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 effectively used as a substrate of a display panel that also has the function of a light guide plate. If so, the component structure of the display device can be simplified.

The glass plate of the present invention is characterized in that the maximum transmittance in the optical path length of 500 mm and the wavelength range of 400 nm to 750 nm is 93% or more. In addition, the glass plate of the present invention is characterized in that the difference between the maximum transmittance and the minimum transmittance in the wavelength range of 400 nm to 750 nm is 6% or less. The technical features of the glass plate of the present invention are described in the description column of the light guide plate of the present invention, and therefore, detailed descriptions are omitted here.

In the glass plate of the present invention, the transmittance at an optical path length of 0.15 mm and a wavelength of 250 nm is preferably 85% or more, 88% or more, 90% or more, 92% or more, 94% or more, 95% or more, especially It is more than 96%. If the transmittance at the optical path length of 0.15 mm and the wavelength of 250 nm is too low, it is difficult to extend to applications requiring sterilization and virus killing. [Example 1]

Hereinafter, the present invention will be explained based on examples. However, the following examples are only examples. The present invention is not limited at all by the following examples.

Table 1 shows examples of the present invention (sample No. 1 to No. 4).

[Table 1]

First, the glass batch material prepared by blending the glass raw materials was put into a platinum crucible so as to have the glass composition in the table, and then melted at 1200°C to 1450°C for 24 hours. When dissolving the glass batch material, a platinum stirrer was used for stirring and homogenization. Next, after flowing the molten glass onto the carbon plate and forming it into a plate shape, it was slowly cooled at a temperature near the slow cooling point for 30 minutes. For each sample obtained, the coefficient of thermal expansion CTE, the strain point Ps in the temperature range of 30°C to 380°C, the maximum transmittance and the minimum transmittance in the wavelength range of 400 nm to 700 nm were evaluated.

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

Based on the above results, samples No. 1 to No. 4 have high strain points and high heat resistance, and have a low thermal expansion coefficient compared with resin plates, so that dimensional changes are difficult to occur with temperature rise, and they are in the wavelength range from 400 nm to 400 nm. The difference between the maximum transmittance and the minimum transmittance in 750 nm is small. Therefore, it can be considered that the samples No. 1 to No. 4 are suitable as light guide plates, especially light guide plates for edge-light type surface light-emitting devices. [Example 2]

First, in terms of mass %, it contains 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, 0.3% SnO ₂ as a form of glass composition, the glass raw materials are prepared and mixed, and then melted in a continuous melting furnace to obtain molten glass. Next, the obtained molten glass is formed into a plate shape by an overflow down-draw method, and after slow cooling, it is cut into a predetermined size, and the surface roughness Ra of the end surface is polished to 0.3 μm to obtain a glass plate. Here, when the glass plate is made, the content of Rh ₂ O ₃ in the glass plate is less than 0.2 ppm, the content of Fe ₂ O ₃ is 5 ppm by mass, and the content of Cr ₂ O ₃ is less than 0.1 ppm. , Use high-purity glass raw materials such as Fe ₂ O _{3 with} few coloring impurities as glass raw materials, and use glass manufacturing equipment designed so that coloring components such as Rh ₂ O ₃ do not mix into the glass from the glass plate manufacturing equipment.

For the obtained glass plate, the UH4150 manufactured by Hitachi High-Tech Science Corporation was used to measure the transmittance in the optical path length of 150 mm and the wavelength range of 400 nm to 750 nm, and then convert it to the optical path length The internal transmittance of 500 mm. As a result, the maximum transmittance in the wavelength range of 400 nm to 750 nm is 99% in the optical path length of 500 mm, and the maximum transmittance and minimum transmittance in the wavelength range of 400 nm to 750 nm. The rate difference is 3%. In addition, the transmittance curve at an optical path length of 500 mm and a wavelength range of 400 nm to 750 nm is shown in Figure 3.

Furthermore, for the obtained glass plate, the thermal expansion coefficient CTE in the temperature range of 30°C to 380°C was measured by the method described above, and the result was 66.3×10 ^-7 /°C, and the strain point was measured to be 536°C.

Based on the above results, it can be considered that the light guide plate having the glass plate is one that is difficult to produce dimensional changes due to temperature rise and can improve the brightness characteristics of the display device. [Example 3]

First, in terms of mass %, it contains 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, 0.3% SnO ₂ as a form of glass composition, the glass raw materials are prepared and mixed, and then melted in a continuous melting furnace to obtain molten glass. Next, the molten glass obtained is shaped into a 0.15 mm thick plate by the overflow down-draw method, and after slow cooling, it is cut into a predetermined size, and the surface roughness Ra of the end surface is polished to 0.3 μm. Obtain a glass plate. Here, when the glass plate is produced, the content of Rh ₂ O ₃ in the glass plate is less than 0.2 ppm, the content of Fe ₂ O ₃ is 4 ppm by mass, and the content of Cr ₂ O ₃ is less than 0.1 ppm. A high-purity glass raw material with few coloring impurities such as Fe ₂ O _{3 is} used as a glass raw material, and glass manufacturing equipment designed so that coloring components such as Rh ₂ O ₃ will not be mixed into the glass from the glass plate manufacturing equipment.

For the obtained glass plate, the U-4100 manufactured by Hitachi High-Technologies Corporation was used to measure the transmittance in the thickness of 0.15mm (optical path length 0.15mm) and the wavelength range of 200nm~700nm, and then convert it Into the internal transmittance. Fig. 4 is data showing the transmittance curve (internal transmittance curve) of the sample in the wavelength range of 200 nm to 700 nm, and Fig. 5 is data showing the external transmittance curve in the wavelength range of 200 nm to 700 nm. In addition, as can be seen from FIGS. 4 and 5, the transmittance (internal transmittance) of this sample at a wavelength of 250 nm is 96%, and the external transmittance is 88%.

Furthermore, for this glass sample, the thermal expansion coefficient CTE in the temperature range of 30 to 380°C was measured by the method described above, and the result was 66.3×10 ^-7 /°C.

According to the above, this glass sample is suitable for applications that require sterilization and virus killing because of the good penetration of deep ultraviolet rays. Furthermore, since the coefficient of thermal expansion is higher than that of quartz glass, the sealing and sealing performance with ceramics or metals is also good. Excellent.

[Industrial availability]

In addition to the light guide plate, the glass plate of the present invention is also suitable for applications requiring high transmittance. For example, it is suitable for glass substrates for displays, glass substrates for optical communication devices, and glass substrates for semiconductor manufacturing processes. In addition, the glass plate of the present invention has a high transmittance in the deep ultraviolet region and a higher thermal expansion coefficient than quartz glass, so it can be extended to a wide range of fields such as medical treatment, analysis, environment, and agriculture. Furthermore, since the glass of the present invention has a high transmittance in the ultraviolet region, it can be processed into a tube shape and can be suitably used as a sterilization lamp.

1‧‧‧Edge light type surface light emitting device 2,12‧‧‧Light source 3,10‧‧‧Light guide plate 4,19‧‧‧Reflective layer 5‧‧‧Diffusion plate (diffusion layer) 6‧‧‧Light reflection surface 7‧‧‧Light exit surface 11‧‧‧Glass plate 13,16,17,18‧‧‧End surface 14‧‧‧Back 15‧‧‧dot pattern

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

10‧‧‧Light guide plate

11‧‧‧Glass plate

12‧‧‧Light source

13, 16, 17, 18‧‧‧end face

14‧‧‧Back

15‧‧‧dot pattern

19‧‧‧Reflective layer

Claims (17)

A light guide plate, characterized by having at least a glass plate, the content of Rh ₂ O ₃ in the glass plate is 0.01 ppm or more and less than 1 ppm by mass, and the optical path length of the glass plate is 100 mm and the wavelength range is 400 nm The difference between the maximum transmittance and the minimum transmittance in ~750nm is 6% or less. The light guide plate as described in item 1 of the scope of patent application, wherein the content of Fe ₂ O ₃ in the glass plate is less than 50 ppm by mass, and the glass plate has a maximum optical path length of 100 mm and a wavelength range of 400 nm to 750 nm The transmittance is over 85%. The light guide plate as described in item 1 or item 2 of the scope of patent application, wherein the content of Cr ₂ O ₃ in the aforementioned glass plate is 5 ppm or less by mass. According to the light guide plate described in item 1 or item 2 of the scope of patent application, a pattern is printed on one of the surfaces of the aforementioned glass plate. According to the light guide plate described in item 4 of the scope of patent application, the diameter of the dots of the aforementioned dot pattern gradually becomes larger as the distance from the end surface where the light from the light source should be incident. The light guide plate as described in item 1 or item 2 of the scope of patent application, wherein the average surface roughness Ra of the end surface of the aforementioned glass plate is 0.5 μm or less. According to the light guide plate described in the first or second patent application, a reflective layer is formed on all or a part of the end surface other than the end surface where light from the light source should be incident. Such as the light guide plate described in item 1 or item 2 of the scope of patent application, wherein the aforementioned glass plate contains 40%~80% SiO ₂ , 1%~15% Al ₂ O ₃ , 0~20% by mass % B ₂ O ₃ , 0-20% Na ₂ O, 0-10% MgO, 0-15% CaO, 0-15% SrO, and 0-35% BaO are used as glass composition. The light guide plate as described in item 1 or item 2 of the scope of patent application, wherein the thermal expansion coefficient of the aforementioned glass plate is 120×10 ^-7 /°C or less. The light guide plate described in item 1 or item 2 of the scope of patent application is used for edge light type surface light emitting devices. A glass plate, characterized in that: the content of Rh ₂ O ₃ in the glass plate is 0.01 ppm or more and less than 1 ppm by mass, and the optical path length of the glass plate is 100 mm and the maximum transmittance in the wavelength range of 400 nm to 750 nm The difference in transmittance from the minimum transmittance is 6% or less, and the maximum transmittance in the optical path length of 500 mm and the wavelength range of 400 nm to 750 nm is 93% or more. As described in the 11th item of the scope of patent application, the content of Fe ₂ O ₃ is 10 ppm or less by mass. For example, the glass plate described in item 11 or item 12 of the scope of patent application has a transmittance of 85% or more in an optical path length of 0.15mm and a wavelength of 250nm. A glass plate, characterized in that: the content of Rh ₂ O ₃ in the glass plate is 0.01 ppm or more and less than 1 ppm by mass, and the optical path length of the glass plate is 100 mm and the maximum transmittance in the wavelength range of 400 nm to 750 nm The difference in transmittance from the minimum transmittance is 6% or less, in which Cr ₂ O ₃ and Fe ₂ O ₃ are included in the glass composition, and the mass ratio Cr ₂ O ₃ /Fe ₂ O ₃ is 0.0435 to 0.13. As for the glass plate described in item 14 of the scope of patent application, the content of Fe ₂ O ₃ in the glass composition is 1 ppm to 10 ppm by mass. The glass plate described in item 14 of the scope of patent application has a maximum transmittance of 95% or more in the optical path length of 500 mm and the wavelength range of 400 nm to 750 nm. The glass plate described in the 14th item of the scope of patent application has a transmittance of 85% or more in an optical path length of 0.15 mm and a wavelength of 250 nm.

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