JP2017043530A - Light guide plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To create a light guide plate that is resistant to dimensional change with a temperature rise, and prevents the brightness properties of a display device from deteriorating.SOLUTION: A light guide plate has at least a glass plate, a RhOcontent in the glass plate is less than 1 ppm in mass, and a difference between a maximum transmittance and a minimum transmittance of the glass plate at an optical path length 100 mm and in a wavelength range 400-750 nm is 12% or less.SELECTED DRAWING: Figure 1

Description

  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, 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 arranged on the light emitting surface side of the surface light emitting device. As the 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 disposed on the back surface opposite to the light emitting surface. When a point light source such as a light emitting diode (Light Emitting Diode) is used as the light source, a large number of LED chips are required to compensate for the brightness, and the variation in luminance characteristics becomes very large.

  For this reason, at present, edge light type surface light emitting devices have become mainstream. The edge light type surface light emitting device includes a light source such as an LED, a light guide plate, and a reflective layer such as a reflective film. A light source is arrange | positioned at the end surface which becomes a orthogonal direction with respect to a light-projection surface (surface). The light guide plate is disposed to take in light from the light source from the end face, propagate the light into the interior by total reflection, and emit the light from the light exit surface in a planar shape. A resin plate such as an acrylic resin is generally used as the light guide plate (see Patent Documents 1 to 4). The reflective layer is disposed on the back side facing the light emitting surface, and is disposed to reflect light passing through the back surface and emit light on a display surface such as a liquid crystal panel. In order to make the display surface of the liquid crystal panel or the like emit light uniformly, a diffusion layer may be disposed on the light exit surface side of the 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 2 such as an LED, a light guide plate 3, a reflection layer 4, and a diffusion layer 5. Light from the light source 2 enters from the end face of the light guide plate 3 and propagates into the light guide plate 3. The light reaching the light reflecting surface 6 is reflected by the reflecting layer 4, travels toward the light emitting surface 7, and is diffused by the diffusion layer 5. As a result, a display surface such as a liquid crystal panel disposed above the diffusion layer 5 can emit light uniformly. A reflective layer may be formed on the end surface opposite to the end surface of the light guide plate 3 on which light from the light source 2 is incident.

JP 2012-123933 A JP 2012-138345 A JP 2012-216523 A JP 2012-216528 A

In the edge light type surface emitting device, when light is generated from the light source, heat is generated, and accordingly, the temperature of the light guide plate also increases. When a resin plate is used as the light guide plate, the dimensional change due to heat of the light guide plate is larger than the dimensional change of the liquid crystal panel. This is due to the high thermal expansion coefficient of the resin plate. For example, the thermal expansion coefficient of the acrylic resin plate is about 700 × 10 ⁻⁷ / ° C. For this reason, until now, a dimensional change of the light guide plate has been corrected by providing a gap in the frame portion of the liquid crystal display device so that an undue stress is not generated due to a difference in dimensional change.

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

  Further, when a resin plate is used as the light guide plate, the amount of light is reduced when light from the light source enters from the end face and exits to the light exit surface. As a result, the luminance characteristics of the display device are likely to deteriorate.

  Therefore, the present invention has been made in view of the above circumstances, and its technical problem is to devise a light guide plate that hardly undergoes dimensional change with a rise in temperature and that does not easily lower the luminance characteristics of the display device. is there.

As a result of intensive studies, the present inventor adopted a glass plate having a small dimensional change due to a temperature change as the light guide plate, and reduced the content of Rh ₂ O _{3 in} the glass plate to increase the transmittance of the glass plate. The inventors have found that the above technical problem can be solved by restricting to a predetermined range, and propose the present invention. That is, the light guide plate of the present invention has at least a glass plate, and 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 maximum in the wavelength range of 400 to 750 nm. The difference between the transmittance and the minimum transmittance is 12% or less. Here, “the maximum transmittance and the minimum transmittance in an optical path length of 100 mm and a wavelength range of 400 to 750 nm” can be measured by a commercially available transmittance measuring device, and can be measured by, for example, UV-3100PC manufactured by Shimadzu Corporation. . “Transmittance” refers to the internal transmittance calculated by Formula 1 unless otherwise specified.

[Formula 1]
logT _in = log (I ₁ / I ₀ ) −logR
logT _in : Internal transmittance (%)
I ₀ : Incident light intensity (%)
I ₁ : Intensity of light after passing through a specific optical path length (%)
R: Light attenuation rate 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 adopted as the light guide plate, a difference in dimensional change between the display panel and the light guide plate is reduced, and it is possible to appropriately cope with a narrow frame of a display device such as a liquid crystal display device.

The inventor has found that the luminance characteristics of the display device are improved when the difference in transmittance of the glass plate in the visible region is small. Furthermore, the present inventor can suitably reduce the transmittance difference of the glass plate in the visible region when Rh ₂ O ₃ in the glass plate greatly affects the absorption near the wavelength of 450 nm and the content is reduced. I found. 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 maximum transmittance and the minimum transmission in the optical path length 100 mm and wavelength range 400 to 750 nm of the glass plate. By limiting the transmittance difference of the rate to 12% or less, the luminance characteristics of the display device are remarkably improved.

Second, the light guide plate of the present invention has a Fe ₂ O ₃ content of less than 50 ppm by mass in the glass plate, and has a maximum transmittance of 85% in an optical path length of 100 mm and a wavelength range of 400 to 750 nm. The above is preferable. If the content of Fe ₂ O _{3 in} the glass plate is reduced, the maximum transmittance in 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 state of Fe ³⁺ or Fe ^{2+ in} the glass. Fe ³⁺ has an absorption peak in the vicinity of a wavelength of 380 nm, and lowers the transmittance in the visible region in the ultraviolet region and the short wavelength side. Fe ²⁺ has an absorption peak in the vicinity of a wavelength of 1080 nm, and lowers the transmittance in the visible region on the long wavelength side. Therefore, when the content of Fe ₂ O ₃ increases, the maximum transmittance in an optical path length of 100 mm and a wavelength range of 400 to 750 nm tends to decrease. In general, a large amount of Fe ₂ O ₃ is mixed in the glass plate from the glass raw material and the manufacturing process. Therefore, the conventional glass plate, because the content of Fe ₂ O ₃ is large, it is difficult to increase the luminance characteristics of the display device. Therefore, when the content of Fe ₂ O ₃ in the glass plate is regulated to be less than 50 ppm by mass, the luminance characteristics of the display device can be improved. Note that “Fe ₂ O ₃ ” referred to in the present invention includes divalent iron oxide and trivalent iron oxide, and the divalent iron oxide is handled in terms of Fe ₂ O ₃ . Similarly, other oxides are handled based on the indicated oxide.

Third, the light guide plate of the present invention preferably has a Cr ₂ O ₃ content in the glass plate of 5 ppm or less by mass. According to the inventor's investigation, Cr ₂ O ₃ in the glass plate greatly affects the absorption near the wavelength of 630 nm, and reducing its content effectively reduces the transmittance difference of the glass plate in the visible range. Can do.

  Fourthly, in the light guide plate of the present invention, it is preferable that a dot pattern is printed on one surface (preferably the light exit surface) of the glass plate. If it does in this way, it will become easy to equalize the light radiate | emitted from a light-projection surface within a surface.

  Fifth, in the light guide plate of the present invention, it is preferable that the dot diameter of the dot pattern gradually increases as the distance from the end face where the light from the light source is incident. If it does in this way, it will become easy to equalize the light radiate | emitted from a light-projection surface within a surface.

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

  Seventhly, in the light guide plate of the present invention, it is preferable that a reflection layer is formed on all or a part of the end face other than the end face on which the light from the light source should enter. If it does in this way, the light which propagated inside the glass plate will become difficult to leak from an end face.

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 through 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 transmittance difference 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 pattern 15 is formed on the back surface 14 of the glass plate 11 facing the light exit surface. The dot diameter of the dot pattern 15 gradually increases from the end surface 13 toward the end surface 16. With this dot pattern 15, the light emitted from the light emitting surface is made uniform in the surface. Further, a reflection layer 19 is formed on each of the end faces 16, 17, and 18 of the glass plate. And the light which reached | attained the end surfaces 16, 17, and 18 of a glass plate is reflected by the reflection layer 19, returns to the inside of the glass plate 11, and finally radiate | emits from a light-projection surface.

  It is also possible to use a plurality of glass plates 11 of the present invention after being joined. For example, two glass plates 11 are prepared, a reflection layer is not formed on the end surface 17 of one glass plate 11, and a reflection layer is not formed on the end surface 18 of the other glass plate 11, and both reflection layers are formed. A large-area light guide plate can be manufactured by joining the end faces that are not bonded with a transparent adhesive having a matched refractive index.

Eighth, in the light guide plate of the present invention, the glass plate has a glass composition of mass%, SiO ₂ 40-80%, Al ₂ O ₃ 1-15%, B ₂ O ₃ 0-20%, Na _2. It is preferable to contain O 0-20%, MgO 0-10%, CaO 0-15%, SrO 0-15%, BaO 0-35%. If it does in this way, the thermal expansion coefficient of a glass plate will fall easily.

Ninthly, in the light guide plate of the present invention, it is preferable that the thermal expansion coefficient of the glass plate is 120 × 10 ⁻⁷ / ° C. or less. Here, “thermal expansion coefficient” refers to a value obtained by measuring an average thermal expansion coefficient at 30 to 380 ° C. based on JIS R3102 using a dilatometer.

  10thly, it is preferable to use the light-guide plate of this invention for an edge light type surface emitting device.

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

Twelfth, the glass plate of the present invention is less than 1ppm in the content of _Rh 2 _{O 3} mass, and it is preferable content of _Fe 2 _{O 3} is 10ppm or less by mass.

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

Fourteenth, the glass plate of the present invention comprises _Cr 2 _{O 3} and _Fe 2 _{O 3} in the glass composition, the mass ratio _{Cr 2 O 3 / Fe 2 O} 3 is 0.01 to 0.13 Is preferred. If the mass ratio Cr ₂ O ₃ / Fe ₂ O ₃ is restricted to 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, the glass plate of the present invention preferably has a content of Fe ₂ O ₃ in the glass composition of 1 to 10 ppm by mass.

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

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

It is a section conceptual diagram showing an example of an edge light type surface emitting device. It is a conceptual perspective view which shows an example of the light-guide plate of this invention. It is data which shows the transmittance | permeability curve in the optical path length 500mm of the sample in the column of Example 2, and the wavelength range 400-750 nm. It is the data which shows the transmittance | permeability curve (internal transmittance | permeability curve) in the plate | board thickness of 0.15 mm and the wavelength range of 200-700 nm in the column of Example 3. FIG. It is data which shows the external transmittance | permeability curve in the plate | board thickness of 0.15 mm in the column of Example 3, and the wavelength range of 200-700 nm.

  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 of the glass plate is preferably 12% or less, 10% or less, 8% or less, 6% or less. 5% or less, particularly 4% or less. If the transmittance difference is too large, the luminance characteristics of the display device are likely to deteriorate.

  The maximum transmittance in an optical path length of 100 mm and a 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% or more, 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 characteristics of the display device are likely to deteriorate.

  The maximum transmittance in an optical path length of 200 mm and a wavelength range of 400 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, 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 characteristics of the display device are likely to deteriorate.

  The maximum transmittance in an optical path length of 500 mm and a wavelength range of 400 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, particularly 99% or more. If the maximum transmittance is too low, the luminance characteristics of the display device are likely to deteriorate.

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

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 preferably 0.8. 1 to 0.3 ppm. If the content of Rh ₂ O ₃ is too large, it tends transmittance difference of the maximum transmittance and the minimum transmittance is excessive in the wavelength range 400 to 750 nm. Note that if too small a content of Rh ₂ O _3, it becomes difficult to use the high-strength Pt-Rh alloy on the glass manufacturing facility, the manufacturing cost of the glass plate is high.

In order to reduce the content of Rh ₂ O ₃ as much as possible, a high-purity glass raw material is used, glass production conditions are adjusted so that Rh ₂ O ₃ is not mixed, or a Pt—Rh alloy in a glass production facility. You can reduce the number of use points.

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 by mass. . When the content of cr ₂ O ₃ is too large, it tends transmittance difference of the maximum transmittance and the minimum transmittance is excessive in the wavelength range 400 to 750 nm. Incidentally, when the content of Cr ₂ O ₃ is too small, the raw material cost, the cost of manufacturing the glass sheet to rise.

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

In the wavelength range of 400 to 750 nm, the transmittance near the wavelength 550 nm is relatively high, and the transmittance near the wavelength 400 nm and the wavelength near 750 nm tends to be relatively low. For this reason, if the transmittance near the wavelength 400 nm and the wavelength 750 nm is increased while the transmittance near the wavelength 550 nm is slightly lowered, the transmittance difference between the maximum transmittance and the minimum transmittance in the wavelength range 400 to 750 nm is made as much as possible. Can be made smaller. According to the inventor's investigation, when Fe ₂ O ₃ is contained in a small amount (preferably 1 to 10 ppm by mass, particularly 2 to 5 ppm), the overall transmittance in the wavelength range of 400 to 750 nm is improved overall. The transmittance in the vicinity of the wavelength of 550 nm can be slightly lowered. Further, when the content of Cr ₂ O ₃ is further reduced, the transmittance in the vicinity of the wavelength of 400 nm and the wavelength of about 750 nm can be increased. 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 outside the above range, the difference in transmittance between the maximum transmittance and the minimum transmittance in the wavelength range of 400 to 750 nm tends to increase.

In order to reduce the content of Cr ₂ O ₃ and Fe ₂ O ₃ as much as possible, high-purity glass raw materials were used, and the glass raw materials were designed not to mix Cr ₂ O ₃ and Fe ₂ O ₃ . A raw material mixing facility or the like may be used. However, if Cr ₂ O ₃ and Fe ₂ O ₃ are to be extremely reduced, there arises a problem that raw material costs and production costs are increased.

In the light guide plate of the present invention, it is preferable to reduce as much as possible 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.

The content of V ₂ O ₅ 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, In particular, it is 0.003 mass% or less. When the content of V ₂ O ₅ is too large, the optical path length 100 mm, the maximum transmittance in the wavelength range 400~750nm tends to decrease.

  The content of NiO 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 preferably It is 003 mass% or less. When there is too much content of NiO, the maximum transmittance | permeability in optical path length 100mm and wavelength range 400-750nm will fall easily.

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 0.003 mass% or less. When the content of MnO ₂ is too large, the optical path length 100 mm, the maximum transmittance in the wavelength range 400~750nm tends to decrease.

The content of Nd ₂ O ₃ 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, In particular, it is 0.003 mass% or less. When the content of Nd ₂ O ₃ is too large, the optical path length 100 mm, the maximum transmittance in the wavelength range 400~750nm tends to decrease.

The CeO ₂ content 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 0.003 mass% or less. When the content of CeO ₂ is too large, the optical path length 100 mm, the maximum transmittance in the wavelength range 400~750nm tends to decrease.

The content of Er ₂ O ₃ 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, In particular, it is 0.003 mass% or less. When the content of Er ₂ O ₃ is too large, the optical path length 100 mm, the maximum transmittance in the wavelength range 400~750nm tends 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. In this way, it is possible to satisfy the demand for an increase in the size of the display device.

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

  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, particularly 590 ° C. or higher. If the strain point is too low, the heat resistance of the glass plate tends to be lowered. For example, when a reflective film, a diffusion film, or the like is formed on the surface or end surface of the glass plate at a high temperature, the glass plate is likely to be thermally deformed. Here, the “strain point” is a value measured based on JIS R3103.

Glass plate, as a glass composition, in _{mass%, SiO 2 40~80%, Al} 2 O 3 1~15%, B 2 O 3 0~20%, Na 2 O 0~20%, MgO 0~10% CaO 0 to 15%, SrO 0 to 15%, BaO 0 to 35% are preferably contained. The reason why the content of each component is regulated as described above will be described below. In addition, in description of the containing range of each component,% display means the mass%.

SiO ₂ is a component that serves as a network former of glass, and is a component that reduces a thermal expansion coefficient and reduces a dimensional change due to heat. It is a component that increases acid resistance and strain point. The preferable lower limit range of SiO ₂ is 40% or more, 60% or more, 65% or more, 67% or more, particularly 70% or more, and the preferable upper limit range is 80% or less, 78% or less, 77% or less, 75%. Hereinafter, it is particularly 73% or less. When the content of SiO ₂ is increased, the high temperature viscosity is increased, the meltability is lowered, and the devitrification blisters of cristobalite are liable to precipitate at the time of 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 are likely to be lowered.

Al ₂ O ₃ is a component that lowers the thermal expansion coefficient and reduces dimensional changes due to heat. It also has the effect of increasing the strain point and suppressing the precipitation of devitrified cristobalite during molding. The preferred 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 preferred upper limit range is 15% or less, 13% or less, particularly 12 % Or less. When the content of Al ₂ O ₃ increases, the liquidus temperature rises and it becomes difficult to form a glass plate. On the other hand, when the content of Al ₂ O ₃ decreases, the thermal expansion coefficient increases and the dimensional change due to heat tends to increase. In addition, the strain point tends to decrease.

B ₂ O ₃ is a component that acts as a flux, lowers the high temperature viscosity, and improves the meltability. Moreover, it is a component which reduces a thermal expansion coefficient and reduces the dimensional change by a heat | fever. The preferred lower limit range of B ₂ O ₃ is 0% or more, 3% or more, 5% or more, 7% or more, 8% or more, particularly 10% or more, and the preferred upper limit range is 15% or less, 13% or less, In particular, it is 12% or less. When the content of B ₂ O ₃ is increased, the strain point and acid resistance are likely to be lowered. On the other hand, when the content of B ₂ O ₃ decreases, the thermal expansion coefficient increases and the dimensional change due to heat tends to increase. In addition, the meltability tends to be lowered.

Na ₂ O is a component that lowers the high temperature viscosity and improves the meltability. The preferred lower limit range of Na ₂ O is 0% or more, 3% or more, 5% or more, 6% or more, 7% or more, particularly 10% or more, and the preferred upper limit range is 20% or less, 18% or less, 16 % Or less, particularly 15% or less. When 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, when the content of Na ₂ O is reduced, the meltability is likely to be lowered.

  MgO is a component that lowers the high temperature viscosity and improves the meltability. The preferred lower limit range of MgO is 0% or more, 0.05% or more, particularly 0.1% or more, and the preferred upper limit range is 10% or less, 6% or less, 2% or less, 1% or less, especially 0. 5% or less. When there is too much content of MgO, devitrification will become easy to precipitate at the time of shaping | molding.

  CaO is a component that improves the meltability by lowering only the high temperature viscosity without lowering the strain point. The preferred lower limit range of CaO is 0% or more, 0.5% or more, 1% or more, particularly 2% or more, and the preferred upper limit range is 15% or less, 14% or less, 13% or less, 8% or less, particularly 5% or less. When there is too much content of CaO, devitrification will become easy to precipitate at the time of fabrication.

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

  BaO is a component that improves chemical resistance and devitrification resistance. The preferable lower limit range of BaO is 0% or more, 0.1% or more, particularly 0.5% or more, and the preferable upper limit range is 35% or less, 30% or less, 20% or less, particularly 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, the meltability tends to be lowered.

  The preferred lower limit range of the total amount of MgO and CaO is 0% or more, 0.1% or more, 0.5% or more, particularly 1% or more, and the preferred upper limit range is 10% or less, 8% or less, 5% Below, 3% or less, especially 2% or less. When there is too little total amount of MgO and CaO, a meltability will fall easily. On the other hand, when the total amount of MgO and CaO is too large, the thermal expansion coefficient and density are unreasonably high, and the devitrification resistance tends to be lowered.

  The preferred 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, particularly 2% or more, and the preferred upper limit range is 35% or less, 20%. Below, 10% or less, especially 5% or less. If the total amount of SrO and BaO is too small, the meltability tends to decrease. On the other hand, when the total amount of SrO and BaO is too large, the thermal expansion coefficient and density are unreasonably high, and the devitrification resistance 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. .

In addition to the above components, other components may be introduced. For example, to lower the liquidus temperature, Y ₂ O ₃ , La ₂ O ₃ , Nb ₂ O ₅ , P ₂ O ₅ are each reduced to 3%, and to lower the melting temperature, Li ₂ O, K ₂ O, Cs ₂ O may be introduced up to 6% each, and As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , F, Cl, etc. may be introduced as a clarifier up to 2% in total. However, As ₂ O ₃ and Sb ₂ O ₃ are environmentally hazardous substances, and when a glass plate is formed by the float process, it is reduced in the float bath to become a metal foreign object, so avoid substantial introduction. More specifically, the content is preferably 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. In this way, it is difficult to produce a temperature difference and composition difference between the front and back surfaces of the glass ribbon during molding, and it becomes easy to form a glass plate that is unpolished and has good surface quality. As a result, the manufacturing cost of the light guide plate is low. And uniform brightness characteristics. The reason for this is that, in the case of the overflow downdraw method, the surface to be the surface does not come into contact with the bowl-like refractory and is molded in a free surface state.

  In addition to the overflow downdraw method, the glass plate can be formed by a slot downdraw method, a float method, a rollout method, a redraw method, or the like. In the float process, a temperature difference and a composition difference between the front and back surfaces of the glass ribbon are likely to occur during molding. However, if the temperature control during the molding is strictly performed, the temperature difference and the composition difference can be reduced.

  In the light guide plate of the present invention, it is preferable that a dot pattern is printed on one surface (preferably a light exit surface) of the glass plate, and the diameter of the dot of the dot pattern is from the end surface where light from the light source should enter. It is more preferable that the distance gradually increases as the distance increases. If it does in this way, it will become easy to equalize the light radiate | emitted from a light-projection surface within a surface. 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 face of the glass plate (preferably the end face to which light from the light source is incident) is preferably 0.5 μm or less, 0.3 μm or less, 0.2 μm or less, particularly 0.1 μm or less. This makes it easy to reduce optical loss when light from the light source enters the end face. Moreover, it becomes easy to form a high-quality reflective layer on the end face.

  For example, when 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. Moreover, when 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 polishing scratches.

  It is preferable that the end surface of the glass plate does not have a chamfered portion. If it does in this way, it will become easy to take in the light from a light source to the inside of a glass plate.

  In the light guide plate of the present invention, a reflection layer is preferably formed on all or a part of the end surface other than the end surface on which light from the light source is incident, and all of the end surfaces other than the end surface on which light from the light source is incident. It is particularly preferable that a reflective layer is formed on the surface. If it does in this way, the light which propagated inside the glass plate will become difficult to leak from an end face. Note that, as the reflective layer, a reflective film may be directly formed on the end face, but a reflective seal may be attached to the end face.

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

  The light guide plate of the present invention can also be used as a substrate of a display panel having the function of the light guide plate. In this way, the member configuration of the display device can be simplified.

  The glass plate of the present invention is characterized by having an optical path length of 500 mm and a transmittance of 93% or more in 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 the wavelength range of 400 to 750 nm is 6% or less. Since the technical features of the glass plate of the present invention have already been described in the description column 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 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, particularly 96% or more. It is. If the transmittance at an optical path length of 0.15 mm and a wavelength of 250 nm is too low, it will be difficult to deploy to applications requiring sterilization and virus killing.

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

  Table 1 shows examples of the present invention (sample Nos. 1 to 4).

  First, after putting the glass batch which prepared the glass raw material into a platinum crucible so that it might become the glass composition in a table | surface, it melted at 1200-1450 degreeC for 24 hours. In melting the glass batch, the mixture was stirred and homogenized using a platinum stirrer. Next, the molten glass was poured onto a carbon plate and formed into a plate shape, and then slowly cooled at a temperature near the annealing point for 30 minutes. About each obtained sample, the thermal expansion coefficient CTE in the temperature range of 30-380 degreeC, the strain point Ps, the maximum transmittance | permeability in the wavelength range of 400-700 nm, and the minimum transmittance | permeability were evaluated.

  The thermal expansion coefficient 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. based on JIS R3102 using a dilatometer. The strain point is a value measured based on JIS R3103.

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

  From the above results, Sample No. 1-4 have a high strain point, high heat resistance, and a low thermal expansion coefficient compared to the resin plate. Therefore, dimensional change hardly occurs with a rise in temperature, and maximum transmittance in a wavelength range of 400 to 750 nm. The transmittance difference of the minimum transmittance is small. Therefore, sample no. 1-4 are considered suitable as a light guide plate, especially as a light guide plate used for an edge light type surface light emitting device.

First, as a glass composition, by mass%, SiO ₂ 69%, Al ₂ O ₃ 5.8%, B ₂ O ₃ 10.2%, CaO 3.1%, Na ₂ O 10.7%, ZnO 0.9 % And SnO ₂ 0.3% were 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 the overflow downdraw method, and after cooling, the glass is cut into predetermined dimensions and the end surface roughness Ra is polished to 0.3 μm. Got. Here, in producing the glass plate, the Rh ₂ O ₃ content in the glass plate is less than 0.2 ppm, the Fe ₂ O ₃ content is 5 ppm by mass, and the Cr ₂ O ₃ content is less than 0.1 ppm. As a glass raw material, a high-purity glass raw material with few colored impurities, such as Fe ₂ O _3, is used, and a colored component such as Rh ₂ O ₃ is not mixed into the glass from the glass plate manufacturing equipment. A designed glass production facility was used.

  About the obtained glass plate, using UH4150 manufactured by Hitachi High-Tech Science Co., Ltd., after measuring the transmittance in an optical path length of 150 mm and a wavelength range of 400 to 750 nm, converted into an internal transmittance of an optical path length of 500 mm, an optical path length of 500 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%. Further, FIG. 3 shows a transmittance curve in an optical path length of 500 mm and a wavelength range of 400 to 750 nm.

Furthermore, about the obtained glass plate, when the thermal expansion coefficient CTE in the temperature range of 30 to 380 ° C. was measured by the above method, it was 66.3 × 10 ⁻⁷ / ° C., and the strain point was measured. 536 ° C.

  From the above results, it is considered that the light guide plate having this glass plate is less likely to undergo dimensional changes with increasing temperature and can improve the luminance characteristics of the display device.

First, as a glass composition, by mass%, SiO ₂ 69%, Al ₂ O ₃ 5.8%, B ₂ O ₃ 10.2%, CaO 3.1%, Na ₂ O 10.7%, ZnO 0.9 % And SnO ₂ 0.3% were prepared and mixed, and then melted in a continuous melting furnace to obtain molten glass. Next, the obtained molten glass is formed into a 0.15 mm thick plate shape by the overflow down draw method, slowly cooled, then cut to a predetermined dimension, and the end surface roughness Ra is polished to 0.3 μm. As a result, a glass plate was obtained. Here, in producing the glass plate, the Rh ₂ O ₃ content in the glass plate is less than 0.2 ppm, the Fe ₂ O ₃ content is 4 ppm by mass, and the Cr ₂ O ₃ content is less than 0.1 ppm. As a glass raw material, a high-purity glass raw material with few colored impurities, such as Fe ₂ O _3, is used, and a colored component such as Rh ₂ O ₃ is not mixed into the glass from the glass plate manufacturing equipment. A designed glass production facility was used.

  About the obtained glass plate, after measuring the transmittance | permeability in plate | board thickness 0.15mm (optical path length 0.15mm) and wavelength range 200-700nm using Hitachi High-Technologies U-4100, it converted into internal transmittance. did. FIG. 4 is data showing a transmittance curve (internal transmittance curve) in the wavelength range 200 to 700 nm of this sample, and FIG. 5 is data showing an external transmittance curve in the wavelength range 200 to 700 nm. As can be seen from FIGS. 4 and 5, the transmittance (internal transmittance) at a wavelength of 250 nm of this sample was 96%, and the external transmittance was 88%.

Furthermore, when the thermal expansion coefficient CTE in the temperature range of 30 to 380 ° C. was measured for this glass sample by the above method, it was 66.3 × 10 ⁻⁷ / ° C.

  From the above, this glass sample is suitable for applications that require sterilization and virus killing because it penetrates deep ultraviolet rays well, and has a higher coefficient of thermal expansion than quartz glass. Excellent sealing and sealing properties.

  The glass plate of the present invention is suitable for applications requiring high transmittance other than the light guide plate. For example, it is suitable for glass substrates for displays, glass substrates for optical communication devices, glass substrates for semiconductor manufacturing processes, and the like. Moreover, since the glass plate of the present invention has a high transmittance in the deep ultraviolet region and a thermal expansion coefficient higher than that of quartz glass, it can be developed in a wide range of fields such as medical treatment, analysis, environment, and agricultural industry. Furthermore, since the glass according to the present invention has high transmittance in the ultraviolet region, it can be processed into a tube shape and suitably used as a sterilizing lamp.

DESCRIPTION OF SYMBOLS 1 Edge light type surface emitting device 2, 12 Light source 3, 10 Light guide plate 4, 19 Reflective layer 5 Diffusing plate 6 Light reflecting surface 7 Light-emitting surface 11 Glass plate 13, 16, 17, 18 End surface 14 Back surface 15 Dot pattern

Claims (17)

It has at least a glass plate, the Rh ₂ O ₃ content in the glass plate is less than 1 ppm by mass, and the transmittance of the maximum transmittance and the minimum transmittance in the optical path length of 100 mm and the wavelength range of 400 to 750 nm. A light guide plate having a difference of 12% or less. The content of Fe ₂ O _{3 in} the glass plate is less than 50 ppm by mass, and the maximum transmittance in an optical path length of 100 mm and a wavelength range of 400 to 750 nm is 85% or more. The light guide plate described in 1. The light guide plate according to claim 1 or 2, wherein the content of Cr ₂ O ₃ of the glass plate in is 5ppm or less by mass.   The light guide plate according to claim 1, wherein a dot pattern is printed on one surface of the glass plate.   5. The light guide plate according to claim 4, wherein the diameter of the dots in the dot pattern gradually increases as the light from the light source is separated from the end surface to which light is incident.   The light guide plate according to claim 1, wherein an average surface roughness Ra of the end face of the glass plate is 0.5 μm or less.   The light guide plate according to any one of claims 1 to 6, wherein a reflection layer is formed on all or a part of the end face other than the end face on which light from the light source is incident. Glass plate, as a glass composition, in _{mass%, SiO 2 40~80%, Al} 2 O 3 1~15%, B 2 O 3 0~20%, Na 2 O 0~20%, MgO 0~10% CaO 0-15%, SrO 0-15%, BaO 0-35% is contained, The light-guide plate in any one of Claims 1-7 characterized by the above-mentioned. 9. The light guide plate according to claim 1, wherein a thermal expansion coefficient of the glass plate is 120 × 10 ⁻⁷ / ° C. or less.   The light guide plate according to claim 1, wherein the light guide plate is used for an edge light type surface light emitting device.   A glass plate having an optical path length of 500 mm and a maximum transmittance of 93% or more in a wavelength range of 400 to 750 nm. The glass plate according to claim 11, wherein the content of Rh ₂ O ₃ is less than 1 ppm by mass, and the content of Fe ₂ O ₃ is 10 ppm or less by mass.   A glass plate, wherein a difference in transmittance between a maximum transmittance and a minimum transmittance in a wavelength range of 400 to 750 nm is 6% or less. The glass plate according to claim 13, wherein Cr ₂ O ₃ and Fe ₂ O ₃ are contained in the glass composition, and the mass ratio Cr ₂ O ₃ / Fe ₂ O ₃ is 0.01 to 0.13. . The glass plate 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.   The glass plate according to any one of claims 13 to 15, wherein the maximum transmittance in an optical path length of 500 mm and a wavelength range of 400 to 750 nm is 93% or more.   The glass plate according to any one of claims 11 to 16, wherein the transmittance at an optical path length of 0.15 mm and a wavelength of 250 nm is 85% or more.