Patent Application
20170066681
1. Field of the Invention
The present disclosure relates to a glass plate for a light guide plate that is to be used for a liquid crystal display.
2. Description of the Related Art
A liquid crystal display includes a liquid crystal panel; a glass plate, as a light guide plate facing the liquid crystal panel; and a light source for irradiating light onto the liquid crustal panel through the glass plate (cf. Patent Document 1 (Japanese Unexamined Patent Publication No. 2004-252383, for example). Light from the light source enters an inner part from an edge surface of the glass plate; repeats surface reflection so as to spread over the whole inner part; and exits from a counter surface of the glass plate facing the liquid crystal panel, so that the liquid crystal panel is uniformly illuminated.
As a method of forming a glass plate, for example, a fusion method, or a float method is used. Additionally, after forming the glass plate, a chemically strengthening process may be applied.
For a case where a glass plate is formed by the fusion method, or for a case where a glass plate is formed by the float method and then the glass plate is chemically strengthened, the glass palte has a three layer structure in a plate thickness direction.
Furthermore, for a case where a glass plate is formed by the fusion method and then the glass plate is chemically strengthened, the glass plate has a five layer structure in the plate thickness direction.
Brightness of the light from the light guide plate with the three layer structure or the five layer structure has been low.
There is a need for a glass plate for a light guide plate such that the brightness of the light from the light guide plate is enhanced.
According to an aspect of the present invention, there is provided a glass plate for a light guide plate including a first glass layer, a second glass layer facing the first glass layer, and a third glass layer, the third glass layer being an intermediate glass layer formed between the first glass layer and the second glass layer, wherein the glass plate is provided with a three layer structure in a plate thickness direction of the glass plate, wherein the glass plate satisfies
t
1C/(t1B1+t1B2+t1C)<0.03 (1);
n1C>n1B1 (2); and
n1C>n1B2 (3),
where t1B1 is a thickness of the first glass layer, t1B2 is a thickness of the second glass layer, t1C is a thickness of the third glass layer, n1B1 is a refractive index of the first glass layer, n1B2 is a refractive index of the second glass layer, and n1C is a refractive index of the third glass layer.
According to an embodiment of the present invention, a glass plate for a light guide plate can be provided such that brightness of light from the light guide plate is enhanced. Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
An embodiment for implementing the present invention is described below by referring to the accompanying drawings. In the drawings, the same or corresponding reference numerals are attached to the same or corresponding configurations, and thereby the descriptions are omitted. In the present specification, the expression “from x to y,” which represents a numerical range, is defined to be a range including the numerical values x and y, which are the lower limit and the upper limit, respectively.
The liquid crystal panel 10 is formed of, for example, an array substrate; a color filter substrate; a liquid crystal layer; and so forth. The array substrate is formed of a substrate; active elements (e.g., thin film transistors (TFT)) that is formed on the substrate; and so forth. The color filter substrate is formed of a substrate; a color filter that is formed on the substrate; and so forth. The liquid crystal layer is formed between the array substrate and the color filter substrate.
The glass plate 20 faces the liquid crystal panel 10. The glass plate 20 is located at a side facing the visible side of the liquid crystal panel 10 (which is also referred to as the rear side). A surface 13 (rear surface) opposite to a display surface (front surface) 11 of the liquid crystal panel 10 and a front surface 21 of the glass plate 20 are arranged to be parallel.
On a rear surface 23 of the glass plate 20, a scattering structure is formed so as to extract light from the light guide plate. As the scattering structure, dots 40 or an irregular structure may be formed on the rear surface 23 of the glass plate 20; alternatively, a plurality of lenses may be formed on the rear surface 23 of the glass plate 20. Each of the dots 40 may include air bubbles or particles for scattering.
The rear surface 23 of the glass plate 20 is parallel to the front surface 21 of the glass plate 20.
The light source 30 irradiates light onto an edge surface 26 of the glass plate 20. The light from the light source 30 enters an inner part from the edge surface 26 of the glass plate 20; repeats surface reflection so as to spread over the entire inner part; and exits from the counter surface (the front surface) 21 of the glass plate 20 facing the liquid crystal panel 10, so that the liquid crystal panel 10 is uniformly illuminated from behind. Between the glass plate 20 and the liquid crystal panel 10, a scattering film, a brightness enhancement film, a reflection type polarizing film, a 3D film, a polarizing plate, and so forth may be located. Behind the glass plate 20, a reflection film may be located, for example. The light source 30, the glass plate 20, and the various types of optical films are collectively referred to as a backlight unit.
As the light source 30, a white LED is used, for example. The white LED may be formed of, for example, a blue LED; and a fluorophore that illuminates in response to receiving light from the blue LED. As the fluorophores, there are that of YAG-based; an oxide; aluminate; nitride; oxynitride; sulfide; oxysulfide; rare earth oxysulfide; halophosphate; chloride, and so forth.
For example, the white LED may be formed of the blue LED; and a yellow fluorophore. Alternatively, the white LED may be formed of the blue LED; a green fluorophore; and a red fluorophore. The light from the latter white LED is obtained by mixing the three primary colors of light, so that the light from the latter white LED is superior in a color rendering property.
As illustrated in
As illustrated in
The glass plate 20 according to the embodiment satisfies the following formulas (1)-(3):
t
1C/(t1B1+t1B2+t1C)<0.03 (1)
b1C>n1B1 (2)
n1C>n1B2 (3)
Here, t1B1 is a thickness of the first glass layer 22; t1B2 is a thickness of the second glass layer 24; t1C is a thickness of the intermediate glass layer 25; n1B1 is a refractive index of the first glass layer 22; n1B2 is a refractive index of the second glass layer 24; and n1C is a refractive index of the intermediate glass layer 25. The refractive indexes are average values of refractive indexes of the respective layers. For comparing the refractive indexes of the respective layers, the refractive indexes may be represented by refractive indexes for the d-line of helium (the wavelength is 587.6 nm) at room temperature. The thickness of each layer is determined by any of the following methods: by using an optical microscope; by using a result of a composition analysis of, for example, zirconia by EPMA described below; or by using a refractive index calculated from a composition analysis by the EPMA described below. The most preferable method is to determine the thickness of each layer by using the refractive index calculated from the composition analysis by the EPMA; however, the thickness of each layer may be determined by using the optical microscope. The thickness of the glass plate 20 (i.e., t1B1+t1B2+t1C) does not affect the brightness of the light guide plate; however, the thickness of the glass plate 20 is preferably greater than or equal to 0.2 mm, so that the stiffness of the glass plate 20 is sufficient. The thickness of the glass plate 20 is preferably less than 5 mm, so that the weight of the glass is moderate weight, and that the glass plate 20 is suitable for forming by the fusion method.
Flow rates of the melted glass 55 flowing down along both side surfaces of the gutter-shaped member 50 are approximately the same, so that the thickness t1B1 of the first glass layer 22 is approximately equal to the thickness t1B2 of the second glass layer 24. However, the thickness t1B1 of the first glass layer 22 may be different from the thickness t1B2 of the second glass layer 24.
Compositions of the melted glass 55 flowing down along both side surfaces of the gutter-shaped member 50 are approximately the same, so that the refractive index n1B1 of the first glass layer 22 is approximately equal to the refractive index n1B2 of the second glass layer 24.
The intermediate glass layer 25 is the foreign material layer, which is formed during molding; and the intermediate glass layer 25 is rich in the component of the gutter-shaped member 50. The gutter-shaped member 50 is formed of, for example, zirconia and so forth. The refractive index n1C of the intermediate glass layer 25, which is rich in the zirconia component, is greater than the refractive index n1B1 of the first glass layer 22 and the refractive index n1B2 of the second glass layer 24 (n1C>n1B1, n1C>n1B2).
The refractive index n1C of the intermediate glass layer 25 is obtained from the composition of the intermediate glass layer 25; more specifically, from a deviation of the composition of the intermediate glass layer 25 from a reference composition (mol %). The composition of the intermediate glass layer 25 is measured by an Electron Probe Micro Analyzer (EPMA). For each component, a product of the deviation from the reference composition and Appen's additivity factor (Source: A. A. Appen: Nisso Tsushinsha (1974) page 318) shown in Table 1 is obtained. The sum of these products is the difference between the refractive index of the intermediate glass layer 25 and the refractive index of the glass with the reference composition. As the reference composition, the composition of the first glass layer 22 or the composition of the second glass layer 24 may be used. Note that, for the composition of the intermediate glass layer 25, compositions may be measured at multiple points that are evenly spaced apart in the thickness direction of the intermediate glass layer 25, and the average of the measured compositions may be used as the composition of the intermediate glass layer 25. A deviation of the refractive index may be considered to be uniform over the entire wavelength spectrum of visible light.
For a case where the glass plate 20 is formed by the fusion method, and the glass plate 20 has the three layer structure in the plate thickness direction, the brightness of the light from the glass plate 20 is enhanced if the above-described formulas (1) through (3) are satisfied, details of which are described below.
The brightness of the light from the glass plate 20 was obtained by simulation analysis. For the simulation analysis, optical ray tracing software (Light Tools: Produced by CYBERNET SYSTEMS CO., LTD.) was used.
It was assumed that the thickness t1B1 of the first glass layer 22 is equal to the thickness t1B2 of the second glass layer 24 (t1B1=t1B2), and that the refractive index n1B1 of the first glass layer 22 is equal to the refractive index n1B2 of the second glass layer 24 (n1B1=n1B2). For the simulation analysis, the refractive index discontinuously varies on the boundary surface between the first glass layer 22 and the intermediate glass layer 25, and on the boundary surface between the second glass layer 24 and the intermediate glass layer 25 so as to simplify the model. However, since the actual refractive index continuously varies, it was assumed that Fresnel reflection does not occur on these surfaces.
A surface light source 30A, which was parallel to an edge surface 26A, was provided at a position separated, by 1 mm, from the edge surface 26A, which was one of mutually parallel edge surfaces 26A and 27A (the size was 2 mm×10 mm, and the distance was 600 mm) of the glass plate 20A. Note that, for a case where a plurality of point light sources are arranged, instead of adopting the surface light source as the light source, the tendency of the result does not change.
As the optical spectrum of the surface light source 30A, the optical spectrum of the white LED was used, which was formed of the blue LED, the red fluorophore, and the green fluorophore. It was assumed that the number of rays entering the edge surface 26A of the glass plate 20A from the surface light source 30A was 250,000. Note that, even if an optical spectrum of a different type of light source is used, the tendency of the result does not change.
Transmittance of the glass plate 20 was calculated based on internal transmittance (the transmission distance was 10 mm) (cf.
The reflectance of light on the edge surface 27A, and left and right side surfaces 28A and 29A of the surfaces of the glass plate 20A was assumed to be 98%, as it was assumed that a reflective tape with reflectance of 98% was pasted on these surfaces. Then, convex lenses were arranged on the rear surface 23A in a hexagonal lattice shape, so that the light was uniformly extracted from the front surface 21A; and the sizes of the convex lenses were set such that, as the distance from the surface light source 30A became greater, the size of the convex lens became greater. Additionally, a light reflecting surface 31A (reflectance 98%), which was parallel to the rear surface 23A, was provided at a position separated from the rear surface 23A by 0.1 mm. The light reflecting surface 31A reflects the light transmitted through the rear surface 23A toward the rear surface 23A. Note that the light reflecting surface 31A corresponds to a reflection sheet in the backlight unit.
Table 2 and
From Table 2 and
The ratio of the thickness of the intermediate glass layer 25 with respect to the plate thickness of the glass plate 20A (t1C/(t1B1+t1B2+t1C)) can be adjusted by adjusting a flow rate and temperature of the melted glass 55 flowing down along both side surfaces of the gutter-shaped member 50. As the flow rate becomes greater, elution from the gutter-shaped member 50 becomes smaller, so that the ratio of the thickness of the intermediate glass layer 25 decreases. Additionally, as the temperature becomes lower, elution from the gutter-shaped member 50 becomes smaller, so that the ratio of the thickness of the intermediate glass layer 25 decreases.
Table 3 and
From Table 3 and
The refractive index n1C of the intermediate glass layer 25 can be adjusted, for example, by adjusting the material of the gutter-shaped member 50. When the gutter-shaped member 50 is formed of zirconia, the intermediate glass layer 25 is richer in the zirconia component compared to the first glass layer 22 and the second glass layer 24, so that the intermediate glass layer 25 has the refractive index that is greater than refractive indexes of the first glass layer 22 and the second glass layer 24.
Note that the brightness of the light from the glass plate 20A can be enhanced by forming a cross-sectional shape of the boundary surface between the first glass layer 22 and the intermediate glass layer 25 to be a wavy surface; and by forming a cross-sectional shape of the boundary surface between the second glass layer 24 and the intermediate glass layer 25 to be a wavy surface. For a case where these boundary surfaces are parallel surfaces, light that enters these boundary surfaces with an incident angle that is greater than or equal to the total reflection angle is confined in the intermediate glass layer 25. However, if the cross-sectional shapes of these boundary surfaces are wavy surfaces, the light can pass through the boundary surfaces after repeating reflection on these boundary surfaces, so that confinement of the light can be suppressed. Here, a period and amplitude of the wave may or may not be constant. As a method of forming the cross-sectional shape of the boundary surface to be a wavy shape, for example, there are a method based on varying a temperature difference between the melted glass flowing down along both side surfaces of the gutter-shaped member 50, a method based on fluctuating the gutter-shaped member 50, and so forth. In the first modified example below, in order to avoid confinement of light, the cross-sectional shape of the boundary surface may be formed to be a wavelike shape. Here, as a method of foaming, in the first modified example described below, the cross-sectional shape of the boundary surface to be a wavy surface, for example, a method can be considered such that crystals containing calcium are caused to be partially precipitated by contacting the glass with moisture, and then the glass is chemically strengthened. The same applies to the second modified example described below.
As illustrated in
As illustrated in
The glass plate 20B according to the modified example satisfies the following formulas (4)-(7):
t
2E1/(t2E1+t2E2+t2B)<0.08 (4)
t
2E2/(t2E1+t2E2+t2B)<0.08 (5)
n2B<n2E1 (6)
n2B<n2E2 (7)
Here, t2E1 is a thickness of the first glass layer 22B; t2E2 is a thickness of the second glass layer 24B; t2B is a thickness of the intermediate glass layer 25B; n2E1 is a refractive index of the first glass layer 22B; n2E2 is a refractive index of the second glass layer 24B; and n2B is a refractive index of the intermediate glass layer 25B. The refractive indexes are average values of refractive indexes of the respective layers. For comparing the refractive indexes of the respective layers, the refractive indexes may be represented by refractive indexes for the d-line of helium (the wavelength is 587.6 nm) at room temperature. The thickness of each layer can be measured by a surface stress measuring device, such as the surface stress measuring meter FSM-6000 produced by Orihara industrial co., ltd. The thickness of the glass plate 20B (i.e., t2E1+t2E2+t2B) does not affect the brightness of the light guide plate; however, the thickness of the glass plate 20B is preferably greater than or equal to 0.2 mm, so that the stiffness of the glass plate 20B is sufficient. The thickness of the glass plate 20B is preferably less than 5 mm, so that the weight of the glass is moderate weight.
For a case where the conditions on the chemical strengthening (e.g., processing temperature, processing time, and processing liquid) are the same for the first glass layer 22B and the second glass layer 24B, the thickness t2E1 of the first glass layer 22B is substantially equal to the thickness t2E2 of the second glass layer 24B. Here, the thickness t2E1 of the first glass layer 22B may be different from the thickness t2E2 of the second glass layer 24B.
For the case where the conditions on the chemical strengthening (e.g., processing temperature, processing time, and processing liquid) are the same for the first glass layer 22B and the second glass layer 24B, the refractive index n2E1 of the first glass layer 22B is substantially equal to the refractive index n2E2 of the second glass layer 24B. Here, the refractive index n2E1 of the first glass layer 22B may be different from the refractive index n2E2 of the second glass layer 24B.
In the first glass layer 22B and the second glass layer 24B, the K component increases and the Na component decreases, compared to the intermediate glass layer 25B. Consequently, the refractive index n2E1 of the first glass layer 22B and the refractive index n2E2 of the second glass layer 24B are greater than the refractive index n2B of the intermediate glass layer 25B (n2B<n2E1, n2B<n2E2).
The refractive index n2E1 of the first glass layer 22B is obtained from a deviation from the refractive index n2B of the intermediate glass layer 25B. The deviation of the refractive index can be obtained by observing, by a transmission-type two-beam interference microscope, how much the interference fringes generated in the first glass layer 22B are deviated from the interference fringes generated in the intermediate glass layer 25B. Specifically, if it is assumed that the interference fringes are deviated by N lines, respectively, the deviation of the refractive index is N×λ/t. Here, λ is the wavelength of the light used for the observation, and t is the thickness of the sample used for the observation. Note that, for the deviation of the refractive index n2E1 of the first glass layer 22B from the refractive index n2B of the intermediate glass layer 25B, deviations may be measured at multiple points in the first glass layer 22B that are evenly spaced apart in the thickness direction of the first glass layer 22B, and the average of these deviations may be used as the deviation. A deviation of the refractive index may be considered to be uniform over the entire wavelength spectrum of visible light.
For a case where the glass plate 20B is formed by the float method and then chemically strengthened, and the glass plate 20B has the three layer structure in the plate thickness direction, the brightness of the light from the glass plate 20B is enhanced if the above-described formulas (4) through (7) are satisfied, details of which are described below.
The brightness of the light from the glass plate 20B was obtained by simulation analysis. For the simulation analysis, optical ray tracing software (Light Tools: Produced by CYBERNET SYSTEMS CO., LTD.) was used. As the simulation analysis model, the model illustrated in
Table 4 and
From Table 4 and
The ratio of the thickness of the first glass layer 22B with respect to the plate thickness of the glass plate 20B (t2E1/(t2E1+t2E2+t2B)) can be adjusted by adjusting conditions on chemical strengthening (e.g., processing temperature, processing time, and processing liquid). As the processing temperature becomes lower, the ion exchange reaction becomes slower, so that the ratio of the thickness of the first glass layer 22B decreases. Furthermore, as the processing time becomes shorter, the thickness of the first glass layer 22B decreases. The same applies to the ratio of the thickness of the second glass plate 24B with respect to the plate thickness of the glass plate 20B (t2E2/(t2E1+t2E2+t2B)).
Table 5 and
From Table 5 and
The first glass layer 41C and the fifth glass layer 45C are compressive stress layers, respectively, formed by the ion-exchanging. The second glass layer 42C, the third glass layer 43C, and the fourth glass layer 44C are tensile stress layers, respectively, formed by the reaction of the formation of the compressive stress layers. The third glass layer 43C is a foreign material layer formed during formation by the fusion method, and the third glass layer 43C is rich in the component eluted from the gutter-shaped member 50.
The glass plate 20C according to the modified example satisfies the following formulas (8)-(16):
t
3C/(t3E1+t3B1+t3C+t3B2+t3E2)<0.03 (8)
t
3E1/(t3E1+t3B1+t3C+t3B2+t3E2)<0.08 (9)
t
3E2/(t3E1+t3B1+t3C+t3B2+t3E2)<0.08 (10)
n3C>n3B1 (11)
n3C>n3B2 (12)
n3E1>n3B1 (13)
n3E1>n3B2 (14)
n3E2>n3B1 (15)
n3E2>n3B2 (16)
Here, t3E1 is a thickness of the first glass layer 41C; t3B1 is a thickness of the second glass layer 42C; t3C is a thickness of the third glass layer 43C; t3B2 is a thickness of the fourth glass layer 44C; t3E2 is a thickness of the fifth glass layer 45C; n3E1 is a refractive index of the first glass layer 41C; n3B1 is a refractive index of the second glass layer 42C; n3C is a refractive index of the third glass layer 43C; n3E2 is a refractive index of the fourth glass layer 44C; and n3E2 is a refractive index of the fifth glass layer 45C. The refractive indexes are average values of refractive indexes of the respective layers. For comparing the refractive indexes of the respective layers, the refractive indexes may be represented by refractive indexes for the d-line of helium (the wavelength is 587.6 nm) at room temperature. The method of measuring each layer is as described above. The thickness of the glass plate 20C (i.e., t3E1+t331+t3C+t332+t3E2) does not affect the brightness of the light guide plate; however, the thickness of the glass plate 20C is preferably greater than or equal to 0.2 mm, so that the stiffness of the glass plate 20C is sufficient. The thickness of the glass plate 20C is preferably less than 5 mm, so that the weight of the glass is moderate weight, and that the glass plate 20C is suitable for forming by the fusion method.
For a case where the conditions on the chemical strengthening (e.g., processing temperature, processing time, and processing liquid) are the same for the first glass layer 41C and the fifth glass layer 45C, the thickness t3E1 of the first glass layer 41C is substantially equal to the thickness t3E2 of the fifth glass layer 45C. Here, the thickness t3E1 of the first glass layer 41C may be different from the thickness t3E2 of the fifth glass layer 45C.
In the first glass layer 41C and the fifth glass layer 45C, the K component increases and the Na component decreases, compared to the second glass layer 42C and the fourth glass layer 44C. Consequently, the refractive index n3E1 of the first glass layer 41C is greater than the refractive index n3E1 of the second glass layer 42C and the refractive index n3B2 of the fourth glass layer 44C.
Similarly, the refractive index n3E2 of the fifth glass layer 45C is greater than the refractive index n3B1 of the second glass layer 42C and the refractive index n3B2 of the fourth glass layer 44C.
For a case where flow rates of the melted glass flowing down along both side surfaces of the gutter-shaped member 50 are approximately the same, the thickness t3B1 of the second glass layer 42C is approximately equal to the thickness t3B2 of the fourth glass layer 44C. However, the thickness t3B1 of the second glass layer 42C may be different from the thickness t3B2 of the fourth glass layer 44C.
Compositions of the melted glass 55 flowing down along both side surfaces of the gutter-shaped member 50 are approximately the same, so that the refractive index n3B1 of the second glass layer 42C is approximately equal to the refractive index n3B2 of the fourth glass layer 44C.
The third glass layer 43C is the foreign material layer, which is formed during molding; and the third glass layer 43C is rich in the component of the gutter-shaped member 50. The gutter-shaped member 50 is formed of, for example, zirconia and so forth. The refractive index n3C of the third glass layer 43C, which is rich in the zirconia component, is greater than the refractive index n3B1 of the second glass layer 42C and the refractive index n3B2 of the fourth glass layer 44C (n3C>n3B1, n3C>n3B2).
For a case where the glass plate 20C is formed by the fusion method and then chemically strengthened, and the glass plate 20C has the five layer structure in the plate thickness direction, the brightness of the light from the glass plate 20C is enhanced if the above-described formulas (8) through (16) are satisfied, details of which are described below.
The brightness of the light from the glass plate 20C was obtained by simulation analysis. For the simulation analysis, optical ray tracing software (Light Tools: Produced by CYBERNET SYSTEMS CO., LTD.) was used. As the simulation analysis model, the model illustrated in
Table 6 and
From Table 6 and
The embodiment of the glass plate for the light guide plate and the liquid crystal display are described above; however, the present invention is not limited to the above-described embodiment, and various modifications and improvements may be made within the scope of the gist of the present invention described in the claims.
For example, the liquid crystal display according to the above-described embodiment is a transmission type; however, the liquid crystal display may be a reflection type, and the glass plate 20 may be located in front of the liquid crystal panel 10. Light from the light source 30 enters the inner part from the edge surface of the glass plate 20; the light exits from the surface (the rear surface) of the glass plate 20 facing the liquid crystal panel 10; and the light uniformly illuminates the liquid crystal panel 10 from the front.
Further, in the above-described embodiment, the light source is the white LED; however, the light source may be a fluorescent tube. Furthermore, the type of the white LED is not particularly limited; and, for example, instead of the blue LED, an ultra violet LED whose wavelength is shorter than the wavelength of the blue LED may be used to cause a fluorophore to emit light. Furthermore, instead of the fluorophore-based white LED, a three-color LED based white LED may be used.
A chemical composition of the glass plate for the light guide plate may be diverse. For example, the glass compositions of the glass layer 22 that is the first glass layer of
As for the preferable compositions of the glass plates, there are the following three types (glass provided with a glass composition A, a glass composition B, and a glass composition C), as typical examples. However, the glass composition of the glass according to the present invention is not limited to the examples of the glass composition shown here.
A glass plate provided with the glass composition A preferably includes, in terms of mass percentage on a basis of oxide, 60% to 80% SiO2; 0% to 7% Al2O3; 0% to 10% MgO; 0% to 20% CaO; 0% to 15% SrO; 0% to 15% BaO; 3% to 20% Na2O; 0% to 10% K2O; 5 ppm to 100 ppm Fe2O3. The refractive index of this glass with respect to d-ray of helium (the wavelength is 587.6 nm) at room temperature is from 1.45 to 1.60. As specific examples, there are examples 1 to 4, and example 15 of Table 7.
Further, a glass plate having the glass composition B preferably includes, in terms of mass percentage on a basis of oxide, 45% to 80% SiO2; Al2O3 which is greater than 7% and less than or equal to 30%; 0% to 15% B2O3: 0% to 15% MgO; 0% to 6% CaO; 0% to 5% SrO; 0% to 5% BaO; 7% to 20% Na2O; 0% to 10% K2O; 0% to 10% ZrO2; and 5 ppm to 100 ppm Fe2O3. The refractive index of this glass with respect to d-ray of helium (the wavelength is 587.6 nm) at room temperature is from 1.45 to 1.60. As specific examples, there are examples 5 to 11 of Table 7.
Further, a glass plate having the glass composition C preferably includes, in terms of mass percentage on a basis of oxide, 45% to 70% SiO2; 10% to 30% Al2O3; 0% to 15% B2O3: 5% to 30% MgO, CaO, SrO, and BaO in total; greater than or equal to 0% and less than 3% Li2O, Na2O, and K2O in total; and 5 ppm to 100 ppm Fe2O3. The refractive index of this glass with respect to d-ray of helium (the wavelength is 587.6 nm) at room temperature is from 1.45 to 1.60. As specific examples, there are examples 12 to 14 of Table 7.
For the glass plate according to the embodiment of the present invention including the above-described components, the composition ranges of the components of the glass composition are described below.
SiO2 is a main component of the glass.
In order to maintain a weather resistance property and a devitrification property of the glass, the content of SiO2 for the glass composition A in terms of mass percentage on a basis of oxide is preferably greater than or equal to 60%, and more preferably greater than or equal to 63%; the content of SiO2 for the glass composition B in terms of mass percentage on a basis of oxide is preferably greater than or equal to 45%, and more preferably greater than or equal to 50%; and the content of SiO2 for the glass composition C in terms of mass percentage on a basis of oxide is preferably greater than or equal to 45%, and more preferably greater than or equal to 50%.
However, in order to facilitate dissolution and to enhance foam quality, and in order to keep the content of ferrous (Fe2+) in the glass to be low, so that the optical property becomes favorable, the content of SiO2 for the glass composition A in terms of mass percentage on a basis of oxide is preferably less than or equal to 80%, and more preferably less than or equal to 75%; the content of SiO2 for the glass composition B in terms of mass percentage on a basis of oxide is preferably less than or equal to 80%, and more preferably less than or equal to 70%; and the content of SiO2 for the glass composition C in terms of mass percentage on a basis of oxide is preferably less than or equal to 70%, and more preferably less than or equal to 65%.
For the glass compositions B and C, Al2O3 is an essential component to enhance the weather resistance property of the glass. In order to maintain a practically required weather resistance property of the glass according to the embodiment, the content of Al2O3 for the glass composition A is preferably greater than or equal to 1%, more preferably greater than or equal to 2%; the content of Al2O3 for the glass composition B is preferably greater than 7%, more preferably greater than or equal to 10%; and the content of Al2O3 for the glass composition C is preferably greater than or equal to 10%, more preferably greater than or equal to 13%.
However, in order to keep the content of ferrous (Fe2+) to be low, so that the optical property becomes favorable and foam quality becomes favorable, the content of Al2O3 for the glass composition A is preferably less than or equal to 7%, and more preferably less than or equal to 5%; the content of Al2O3 for the glass composition B is preferably less than or equal to 30%, and more preferably less than or equal to 23%; and the content of Al2O3 for the glass composition C is preferably less than or equal to 30%, and more preferably less than or equal to 20%.
Ba2O3 is a component for promoting melting of the glass materials, so that a mechanical property and the weather resistance property are enhanced; however, in order to prevent generation of a ream by volatilization, and to prevent occurrence of inconvenience, such as corrosion of a furnace wall, the content of Ba2O3 for the glass composition A is preferably less than or equal to 5%, and more preferably less than or equal to 3%; and the content of Ba2O3 for the glass compositions B and C is preferably less than or equal to 15%, and more preferably less than or equal to 12%.
The alkali metal oxides, such as Li2O, Na2O, and K2O, are useful components for promoting melting of the glass materials, and for adjusting thermal expansion and viscosity of the glass materials.
Thus, the content of Na2O for the glass composition A is preferably greater than or equal to 3%, and more preferably greater than or equal to 8%. The content of Na2O for the glass composition B is preferably greater than or equal to 7%, and more preferably greater than or equal to 10%. However, in order to maintain the clarity during melting, and to maintain the foam quality of the glass to be produced, the content of Na2O for the glass compositions A and B is preferably less than or equal to 20%, and more preferably less than or equal to 15%; and the content of Na2O for the glass composition C is preferably less than or equal to 3%, and more preferably less than or equal to 1%.
Further, the content of K2O for the glass compositions A and B is preferably less than or equal to 10%, and more preferably less than or equal to 7%; and the content of K2O for the glass composition C is preferably less than or equal to 2%, and more preferably less than or equal to 1%.
Further, though Li2O is an optional component, less than or equal to 2% Li2O may be included in the glass compositions A, B, and C, so as to facilitate vitrification, to suppress the iron content contained as impurities derived from raw materials to be a low level, and to reduce the batch cost to be low.
Furthermore, in order to maintain the clarity during melting, and to maintain the foam quality of the glass to be produced, the total content of these alkali metal oxides (Li2O+Na2O+K2O) for the glass compositions A and B is preferably from 5% to 20%, and more preferably from 8% to 15%; and the total content of these alkali metal oxides (Li2O+Na2O+K2O) for the glass composition C is preferably from 0% to 2%, and more preferably from 0% to 1%.
The alkali earth metal oxides, such as MgO, CaO, SrO, and BaO, are useful components for promoting melting of the glass materials, and for adjusting thermal expansion, viscosity, and so forth of the glass materials.
MgO affects to promote melting by lowering viscosity during melting of the glass. In addition, MgO affects to reduce a specific gravity, and to prevent the glass plate from being scratched, so that MgO may be included in the glass compositions A, B, and C. Furthermore, the content of MgO for the glass composition A is preferably less than or equal to 10%, and more preferably less than or equal to 8%; the content of MgO for the glass composition B is preferably less than or equal to 15%, and more preferably less than or equal to 12%; and the content of MgO for the glass composition C is preferably less than or equal to 10%, and more preferably less than or equal to 5%, so that the thermal expansion coefficient of the glass can be small and the devitrification property can be favorable.
Since CaO is a component that promotes melting of the glass materials, and that adjusts viscosity, thermal expansion, and so forth of the glass materials, CaO may be included in the glass compositions A, B, and C. In order to obtain the above-described effects, the content of CaO for the glass composition A is preferably greater than or equal to 3%; and more preferably greater than or equal to 5%. Additionally, in order to improve the devitrification, the content of CaO for the glass composition A is preferably less than or equal to 20%, and more preferably less than or equal to 10%; and the content of CaO for the glass composition B is preferably less than or equal to 6%, and more preferably less than or equal to 4%.
SrO affects to increase the thermal expansion coefficient, and to lower high-temperature viscosity of the glass. In order to obtain such effects, SrO may be included in the glass compositions A, B, and C. However, in order to suppress the thermal expansion coefficient to be small, the content of SrO for the glass compositions A and C is preferably less than or equal to 15%, and more preferably less than or equal to 10%; and the content of SrO for the glass composition B is preferably less than or equal to 5%, and more preferably less than or equal to 3%.
Similar to SrO, BaO affects to increase the thermal expansion coefficient, and to lower high-temperature viscosity of the glass. In order to obtain the above-described effects, BaO may be included in the glass compositions A, B, and C. However, in order to suppress the thermal expansion coefficient to be small, the content of BaO for the glass compositions A and C is preferably less than or equal to 15%, and more preferably less than or equal to 10%; and the content of BaO for the glass composition B is preferably less than or equal to 5%, and more preferably less than or equal to 3%.
Furthermore, in order to suppress the thermal expansion coefficient to be small, to make the devitrification property favorable, and to maintain robustness, the total content of these alkali earth metal oxides (MgO+CaO+SrO+BaO) for the glass composition A is preferably from 10% to 30%, and more preferably from 13% to 27%; the total content of these alkali earth metal oxides (MgO+CaO+SrO+BaO) for the glass composition B is preferably from 1% to 15%, and more preferably from 3% to 10%; and the total content of these alkali earth metal oxides (MgO+CaO+SrO+BaO) for the glass composition C is preferably from 5% to 30%, and more preferably from 10% to 20%.
In the glass composition of the glass of the glass plate according to the embodiment of the present invention, in order to enhance the heat resistance and surface hardness of the glass, each of the glass compositions A, B, and C may include less than or equal to 10% ZrO2, preferably less than or equal to 5% ZrO2, as an optional component. However, if the content of ZrO2 exceeds 10%, the glass tends to devitrify, so that it is not preferable.
In the glass composition of the glass of the glass plate according to the embodiment of the present invention, in order to enhance the melting property of the glass, each of the glass compositions A, B, and C may include 5 ppm to 100 ppm Fe2O3. Here, the content of Fe2O3 refers to the whole quantity of iron oxide in terms of Fe2O3. The whole quantity of iron oxide is preferably from 5 ppm by mass to 50 ppm by mass, and more preferably from 5 ppm by mass to 30 ppm by mass. If the above-described whole quantity of iron oxide is less than 5 ppm, the infrared light absorption property of the glass is extremely deteriorated, it becomes difficult to enhance the melting property of the glass, and a large cost is required to purify the raw materials, so that it is not preferable that the whole quantity of iron oxide be less than 5 ppm. Furthermore, if the whole quantity of iron oxide exceeds 100 ppm, coloration of the glass becomes significant, and the visible light transmittance is reduced, so that it is not preferable that the whole quantity of iron oxide exceeds 100 ppm.
Further, the glass of the glass plate according to the embodiment of the present invention may include SO3, as a clarifying agent. In this case, the content of SO3, in terms of mass percentage, is preferably greater than 0% and less than or equal to 0.5%. The content of SO3 is more preferably less than or equal to 0.4%, further more preferably less than or equal to 0.3%, and particularly preferably less than or equal to 0.25%.
Further, the glass of the glass plate according to the embodiment of the present invention may include one or more of Sb2O3, SnO2, and As2O3, as an oxidizing agent and a clarifying agent. In this case, the content of Sb2O3, SnO2, and As2O3, in terms of mass percentage, is preferably from 0% to 0.5%. The content of Sb2O3, SnO2, and As2O3 is more preferably less than or equal to 0.2%, and further more preferably less than or equal to 0.1%; and it is further more preferable that Sb2O3, SnO2, and As2O3 be substantially not included.
However, Sb2O3, SnO2, and As2O3 affect as the oxidizing agent of the glass, so that Sb2O3, SnO2, and As2O3 may be added within the above-described range so as to adjust the amount of Fe2+ of the glass. However, As2O3 may not be positively included due to environmental concern.
Furthermore, the glass of the glass plate according to the embodiment of the present invention may include NiO. When NiO is included, NiO functions as a coloring component, so that the content of NiO is preferably less than or equal to 100 ppm with respect to the total amount of the glass composition described above. In particular, from the viewpoint that NiO does not cause the internal transmittance of the glass plate at a wavelength from 400 nm to 700 nm to be lowered, the content of NiO is preferably less than or equal to 1.0 ppm, and more preferably less than or equal to 0.5 ppm.
Furthermore, the glass of the glass plate according to the embodiment of the present invention may include Cr2O3. When Cr2O3 is included, Cr2O3 functions as a coloring component, so that the content of Cr2O3 is preferably less than or equal to 10 ppm with respect to the total amount of the glass composition described above. In particular, from the viewpoint that Cr2O3 does not cause the internal transmittance of the glass plate at a wavelength from 400 nm to 700 nm to be lowered, the content of Cr2O3 is preferably less than or equal to 1.0 ppm, and more preferably less than or equal to 0.5 ppm.
The glass of the glass plate according to the embodiment of the present invention may include MnO2. When MnO2 is included, MnO2 functions as a component that absorbs visible light, so that the content of MnO2 is preferably less than or equal to 50 ppm with respect to the total amount of the glass composition described above. In particular, from the viewpoint that MnO2 does not cause the internal transmittance of the glass plate at a wavelength from 400 nm to 700 nm to be lowered, the content of MnO2 is preferably less than or equal to 10 ppm.
The glass of the glass plate according to the embodiment of the present invention may include TiO2. When TiO2 is included, TiO2 functions as a component that absorbs visible light, so that the content of TiO2 is preferably less than or equal to 1000 ppm with respect to the total amount of the glass composition described above. In particular, from the viewpoint that TiO2 does not cause the internal transmittance of the glass plate at a wavelength from 400 nm to 700 nm to be lowered, the content of TiO2 is preferably less than or equal to 500 ppm, and more preferably less than or equal to 100 ppm.
The glass of the glass plate according to the embodiment of the present invention may include CeO2. CeO2 affects to decelerate the Redox (the reduction-oxidation reaction) of iron, and CeO2 can reduce the absorption of the glass at a wavelength from 400 nm to 700 nm. However, if a large amount of CeO2 is included, CeO2 also functions as a component to absorb visible light, and CeO2 may lower the Redox of iron to be less than 3%, so that it is not preferable that the large amount of CeO2 be included. Thus, the content of CeO2 is preferably less than or equal to 1000 ppm with respect to the total amount of the glass composition described above. Furthermore, the content of CeO2 is more preferably less than or equal to 500 ppm, further more preferably less than or equal to 400 ppm, particularly preferably less than or equal to 300 ppm, and most preferably less than or equal to 250 ppm.
The glass of the glass plate according to the embodiment of the present invention may include at least one component selected from a group formed of CoO, V2O5, and CuO. When CoO, V2O5, and CuO are included, CoO, V2O5, and CuO function as components for absorbing visible light, so that the content of CoO, V2O5, and CuO is preferably less than or equal to 10 ppm with respect to the total amount of the glass composition described above. In particular, it is preferable that CoO, V2O5, and CuO be substantially not included in the glass, so that the internal transmittance of the glass plate for a wavelength from 400 nm to 700 nm is not lowered.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-116095 | Jun 2014 | JP | national |
The present application is a continuation application filed under 35 U.S.C. 111(a) claiming benefit under 35 U.S.C. 120 and 365(c) of PCT International Application No. PCT/JP2015/063913 filed on May 14, 2015 and designating the U.S., which claims priority of Japanese Patent Application No. 2014-116095 filed on Jun. 4, 2014. The entire contents of the foregoing applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2015/063913 | May 2015 | US |
| Child | 15353033 | US |
