JPS6335581B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has a highly safe reflective coating that does not cause thermal cracking due to temperature rise due to solar radiant heat, and even if a crack occurs in the glass plate, the crack will not move on its own, and the reflected image will be less distorted. This relates to glass plates. For example, heat ray reflective glass plates in which a coating with excellent heat ray reflection performance is formed on the surface of the glass plate are often used as window glass plates for various buildings, residences, and the like. This heat-reflecting glass plate blocks solar radiant energy by reflecting it with the heat-reflecting coating formed on the surface of the glass plate and absorbing it by the glass itself, which reduces the amount of heat flowing into the room and reduces the cooling load. In addition, the heat ray reflective coating provides a unique reflective color tone, and when combined with its mirror effect, a highly impressive effect is obtained.The anti-glare performance of the heat ray reflective coating also improves the indoor environment. A qualitative improvement effect can be obtained. Among these heat-reflecting glasses, for medium and high-rise buildings,
Window glass plates with a special thickness of about 8 to 20 mm are required to have high wind pressure resistance. However, when such an extra-thick glass plate is used, there is a risk that the glass plate will thermally crack due to the temperature increase of the glass itself due to solar radiant heat, and there is also a drawback that the weight of the glass plate increases. In particular, heat-reflecting glass plates that use heat-absorbing glass plates that have a high absorption rate for solar radiant heat, and heat-reflecting glass plates that have a heat-reflecting coating on the indoor side, have increased heat resistance due to their increased thickness. Increased risk of cracking. This thermal cracking occurs because of the heat absorption properties of the glass plate, so if the central part of the glass plate becomes extremely hot, it will expand, but on the other hand, the periphery of the glass plate is inside the sash and is not exposed to sunlight. In addition, heat is radiated to the sash and the frame, which remains at a low temperature.For this reason, the peripheral area restricts the thermal expansion of the central area, creating tensile stress, and the strength of this peripheral area is insufficient to withstand this tensile stress. This is what happens when something is gone. Although it is possible to use an air-cooled tempered glass plate to prevent such heat cracking,
When air-cooled tempered glass sheets break, they break into many small pieces, so if wind-cooled tempered glass sheets are used in high-rise buildings, there is a risk that the glass sheets and fragments will fall from the windows of the high-rise building when they break, and that the strengthening process This is undesirable because it has the drawback that the glass plate warps and distorts during heating and cooling, resulting in reflection distortion. Furthermore, by using a semi-tempered glass plate with a low degree of reinforcement to the extent that it does not break into small pieces when broken, the risk of falling fragments can be somewhat alleviated; however, when manufacturing such a semi-tempered glass plate, Because the glass is heated to about 580°C to 650°C and is rapidly cooled after heating, the glass plate tends to warp or deform.In a heat-reflective glass plate with a heat-reflecting coating formed on the surface of such a semi-tempered glass plate, heat-reflecting Since the visible light reflectance of the coating is high, the warping and deformation of the glass plate becomes more noticeable as a distortion of the reflected image compared to a normal raw glass plate, which greatly reduces the quality of the glass plate. In view of the above-mentioned points, the present invention has thermal crack prevention properties that do not cause any practical problems, and even if a crack occurs in the glass plate, the crack does not move on its own, and the reflection distortion is small and is similar to that of a raw glass plate. It was invented as a result of research with the aim of providing a glass plate that has a reflective image, is thinner and lighter than a special thick glass plate, and has sufficient wind pressure resistance. The gist is that the plate thickness is 5mm to 12mm,
A coated glass plate having a solar absorption rate of at least 55% and a visible light reflectance of 10% or more, and a planar compressive stress in the peripheral area of the glass plate of 50% to 50%.
150 Kg/cm ² , and a surface compressive stress of 30 to 100 Kg/cm ² . The present invention will be explained in more detail below. Glass plates to which the present invention can be preferably applied include various types of glass plates such as soda lime silicate, porosilicate, and alumino silicate glass, which are used for architecture, various vehicles, and industry, and are the most widely used glass plates. It is a soda lime silicate glass plate that is
5mm or more, which is more likely to cause thermal cracking, but thinner than conventional extra-thickness glass plates (for example, 12mm to 20mm), which can make it lighter, particularly preferably 5mm.
It has a plate thickness of ~12mm and a solar absorption rate of at least 55%, that is, an absorption rate of infrared rays in the wavelength range of 0.78μ to 2.5μ.It has a coating that is easily heated to high temperatures due to its heat absorption properties and has a mirror effect. Glass plates having a visible light reflectance of 10% or more, such as metal coatings, alloy coatings, metal oxide coatings, nitride coatings, boride coatings, carbide coatings, and various other compound coatings or coatings of various paints. multiple layers,
Alternatively, a combination layer of these coatings is formed on a transparent colorless glass plate with a smooth and flat surface, a transparent colored glass plate such as a heat ray absorbing glass plate, or an opaque colored glass plate, such as a coated glass plate with a heat ray reflective coating. , a glass plate with a visible light reflecting coating, a colored coating, a conductive coating, a selective transmission coating, etc., or a heat ray absorbing glass plate. In the present invention, the central part of such a coated glass plate is heated by sunlight irradiation and becomes high temperature, but the above-mentioned thermal cracking that occurs when the peripheral part remains low temperature is suppressed. , so that it can be used without any practical problems even if the solar absorption rate is 55% or more, the plane compressive stress that is formed on the peripheral surface in the plane direction, that is, within 2 cm inside from the edge of the glass plate. The maximum plane compressive stress in the peripheral area of the glass plate is controlled to be in the range of 50Kg/cm ² to 150Kg/cm ² . On the other hand, the planar tensile stress generated in the inner region of the planar compressive stress region at the periphery of the glass plate is preferably 60 Kg/cm ² or less to prevent a decrease in the strength of the glass plate. Normally, the surface area of glass plates used for construction etc. is 1.0 m2 ^or more, so it is necessary to deal with the plane compressive stress that is formed in the peripheral area of the glass plate, especially within 2 cm from the end face. As mentioned above, the plane tensile stress generated inside it is less than 60Kg/ ^cm2 ,
This level of plane tensile stress has little practical effect in terms of strength reduction. In addition, in the present invention, the wind pressure resistance strength and thermal crack prevention properties are improved, and on the other hand, even if a crack occurs in the glass plate, the crack does not move on its own and glass plate fragments do not fall, and the glass plate is In order to prevent distortion, the surface compressive stress in the cross-sectional direction of the glass plate is preferably in the range of 30 Kg/cm ² to 100 Kg/cm ² . If this surface compressive stress is greater than 100Kg/cm ² , when the glass plate breaks and a crack occurs, there is a risk that the crack will run on its own and pieces of ^the glass plate will fall. When a large surface compressive stress is generated, it is undesirable because distortion occurs in the glass plate when it is heated or cooled, and when it is lower than 30 kg/ ^cm2 , the wind pressure resistance, especially the plate thickness is ~12 mm, it decreases and is not practical. For example, if the plate thickness is 8mm
In the case of a glass plate with a surface compressive stress of 0 Kg/cm ² , the allowable load is 800 Kg/m ² , which is lower than the practically required allowable load of 1050 Kg/m ² . like this
By applying a surface compressive stress of 30 Kg/cm ² to 100 Kg/cm ² , the wind pressure resistance strength can be increased, and the glass plate can be made thinner. For example, a 12 mm thick glass plate can be replaced with a 10 mm glass plate of the present invention. Note that in order to generate surface compressive stress of about 30Kg/cm ² to 100Kg/cm ² as described above, it is necessary to perform heat treatment such as heating and cooling the glass plate, but it is not possible to generate surface compressive stress in this range. If the heat treatment is carried out to a certain extent, it is possible to suppress the occurrence of warpage, distortion, or other deformation in the glass plate during the heat treatment, and it is possible to reduce reflection distortion. Each stress value of the glass plate described above means the average value of the values measured at each point. Note that the above-mentioned allowable load is determined by the following formula. P=K/FA (t+t ² /4), W=P×A P: Strength when subjected to wind pressure (Kg/m ² ), A: Area of glass plate (m ² ), t: Strength of glass plate Thickness (mm), F: Safety factor (average breaking wind pressure/allowable wind pressure) = 2.5, W: Average breaking load (Kg/cm ² ), K: In the case of a float glass plate with a thickness of 8 mm, K =
80. Next, the present invention will be explained in comparison with a comparative example. Conventionally known plain glass made of soda lime silicate glass is heated to a temperature above the strain point or near the softening point, e.g. 600℃ to 700℃.
A tempered glass plate that is heated to ℃ and then immediately quenched and strengthened by blowing air on both sides of the glass plate has a surface compressive stress of 1000Kg/cm ² to 1500Kg/cm ² and a surface compressive stress in the center of the cross-sectional direction. Although it has a tensile stress of approximately 1/2 of that of the tempered glass sheet, and has sufficient wind pressure strength and thermal crack prevention properties, when this tempered glass sheet breaks, the cracks that occur in the glass sheet will propagate by themselves. The fracture density is uniquely determined by the magnitude of the central tensile stress, for example 40 to 200.
It breaks into pieces with 5cm square pieces, and there is a high risk of falling glass fragments. In addition, the semi-tempered glass plate has a surface compressive stress of 300 to 600 kg/ ^cm2 and a stress of 250 to 400 kg/cm2.
It has a central tensile stress of Kg/cm ² and a ratio of surface compressive stress/central tensile stress of less than 1.5, and has wind pressure strength and thermal cracking resistance that are not inconvenient in practical use, and also has fine fragments when broken. However, if a crack occurs in the glass plate, there is a risk that the crack will propagate and reach the edge of the glass plate, causing large fragments of the glass plate to fall. In addition, the present applicant previously proposed in Japanese Patent Application No. 113995/1987 that it has wind pressure strength and thermal cracking prevention properties that do not pose a problem in practical use, and that even if a crack occurs in the glass plate, the crack will be self-propelled. A highly safe glass plate, that is, a plate thickness of 5 mm or more and less than 10 mm, whose central tensile stress is controlled to be low between 85 and 200 Kg/ ^cm2 , and whose surface compressive stress σc and central tensile stress σt are The ratio σc/σt is controlled in the range of 1.5 to 3.0, and the surface compressive stress is in the range of 127 to 600Kg/ ^cm2 .
More preferably, a heat-treated glass plate with a pressure as low as 250 to 350 Kg/cm ² was proposed. Although this heat-treated glass plate satisfies the above-mentioned performance aspects, when a coating with high visible light reflectance such as a heat ray reflective coating is formed, the surface compressive stress in the range of 127 to 600 kg/cm ² is generated. For example, heat treatment at 580℃ to 680℃ is carried out by transporting the glass plate in a roller hearth or by transporting it in a heating furnace while suspended from a hanger.
Warping or deformation of the glass plate that occurs during heat treatment at a temperature of ℃ and subsequent cooling treatment, etc.
Although not as strong as tempered glass or semi-tempered glass,
It was found that the reflected image was distorted and the quality of the product was degraded. For example, we conducted a reflective strain measurement test on a heat-treated glass plate that had about 1/4 the strength of the above-mentioned normal tempered glass and had a heat-reflecting coating made of Cr on its surface. The results are as shown in Figure 3g, and the distortion of the reflected image in the peripheral area was noticeable. The glass plate sample used in the measurement consisted of a roller hearth 2 having a conveyor roll 1 as shown in FIG. A soda lime silicate glass plate 8 (dimensions: 8mm×900
mm x 1800 mm) is heated to approximately 645°C while horizontally conveyed inside the roller hearth 2 by the conveyor roller 1, and then taken out from the roller hearth and transferred between the first cooling outlets 4. was sprayed on both sides of the glass plate 8 to give 180kcal/ ^m2 .
The glass plate 8 is cooled for 10 seconds with a cooling capacity of hr.°C, and then placed in a heat treatment furnace 5 maintained at a temperature of approximately 470°C.
The glass plate 8 was transferred to the furnace 5 and held for 5 minutes to slowly cool the glass plate 8 until the surface temperature of the glass plate 8 reached approximately 420°C.
When the temperature has dropped to ℃, the glass plate is taken out from the heat treatment furnace, further cooled by blowing air in the second cooling nozzle 6, and a metal Cr film with a thickness of 200 Å is deposited on the surface of the heat-treated glass plate using a vacuum evaporation method. It has a central tensile stress of 175 Kg/cm ² and a surface compressive stress of 37 Kg/cm ² .
(This sample will be referred to as Sample 7.) In the reflection strain measurement test, a plate-shaped body with a checkered pattern (a plate-shaped body for measuring reflection strain in which a grid of 50 mm width is formed at a pitch of 200 mm vertically and horizontally) is vertically The reflected image of the lattice of the above-mentioned lattice-patterned plate reflected on the sample glass plate was placed vertically 40 m away from the sample glass plate for measurement, which was set up in the vicinity of the above-mentioned lattice-patterned plate. It is taken with a camera,
The results were drawn up based on the photographs obtained. (Figure 3) On the other hand, the coated glass plate of the present invention has a thickness of 5 to 12 mm, a solar absorption rate of at least 55%, is susceptible to thermal cracking, and has a low visible light reflectance.
Even if it is a glass plate with a coating where the distortion of the reflected image due to warping or deformation of the glass plate is easily noticeable at 10% or more, the plane compressive stress in the peripheral area is 50Kg/cm ² ~
The surface compressive stress is also controlled between 30Kg/cm ² and 100Kg/cm ² , and more preferably ^the central tensile stress is also 60Kg/cm 2 .
cm ² or less, so as shown in Samples 1 to 6 of the examples shown below, it has practically sufficient wind pressure strength and thermal crack prevention properties, and the property that the crack will not propagate by itself even if a crack occurs in the glass plate. and low reflection distortion can be obtained. In manufacturing the base glass for the coated glass plate of the present invention, the glass temperature is preferably 500 to 580°C, so that plane compressive stress, surface compressive stress, and central tensile stress in the peripheral area are obtained within a predetermined range. is 540～
The glass is heated to 560°C, then placed in a slow cooling furnace with an atmosphere of 400°C to 450°C, and the glass temperature is increased to 400°C to 450°C.
It is preferable to cool the product to 490°C, preferably 420 to 440°C, and then put it into a slow cooling furnace at 250 to 300°C for cooling. In particular, when heating a glass plate, hanging marks are generated and the reflected image is significantly distorted.Instead of heating the glass plate by suspending it from a hanger, it is heated by conveying it on rollers or on a hearth block. A horizontal conveyance heating method in which heating is performed while heating is preferred. Example 6 using the glass plate heat treatment equipment shown in Figure 2.
two soda lime silicate glass plates (horizontal)
1829 mm, length 914 mm) were heat treated under the conditions shown in Table 1. Heat ray reflective coatings made of Cr metal films of various thicknesses were formed on the surfaces of the glass plates thus obtained by vacuum evaporation. Regarding the coated glass plate obtained in this way, visible light reflectance, solar radiation absorption rate, plane compressive stress in the peripheral area, surface compressive stress,
Center tensile stress, permissible load that indicates wind pressure resistance (probability of fracture less than 1/1000), thermal cracking test results (temperature difference between the center and periphery of the glass plate until thermal cracking), reflective strain measurement test, and JIS - The destructive test results (fracture pattern) specified in 6-5 of R-3206 are
Shown in the table and drawings. In addition, the glass plate heat treatment apparatus shown in FIG.
This is shown as a specific example of the apparatus used for heat treatment when manufacturing the coated glass plate of the present invention, and in the figure, 10 indicates a glass plate to be heat treated,
11 is a roller hearth, 12 is a conveying roller for the glass plate, 13 is a heating device for the glass plate, and 14 is a first
, 15 is a second lehr, and 16 is a third lehr. According to this apparatus, the glass plate 10 to be heat-treated is heated to a temperature sufficient to heat-treat the glass plate while being horizontally conveyed by the conveying roller 12 in the roller hearth 11 or while being horizontally slid. Heated to ~580℃. The glass plate 10 taken out from the roller hearth 11 is moved to a first slow cooling furnace 14 with a temperature of 400 to 450°C provided adjacent to the exit of the roller hearth, where it is slowly cooled for 200 to 300 seconds, and then the temperature is reduced to 250 to 300°C.
It is moved to the second annealing furnace 15 at a temperature of 100 to 150 degrees Celsius, where it is cooled for 200 to 300 seconds, and then transferred to the third annealing furnace 16 whose temperature is 100 to 150 degrees Celsius, where it is further annealed to adjust the generated stress and cool the surface of the glass plate. When the temperature reaches 150 to 200°C, it is taken out from the third lehr 16 and left to cool to obtain a glass plate having a predetermined stress value as in the present invention. FIG. 5 shows the results of measuring edge compression at various points around the glass plates of Samples 2 and 4. The unit of values in the figure is Kg/cm ² .

[Table] As shown in Figure 3 a to f, the coated glass plate of the present invention has less distortion of the reflected image than the comparative sample 7, and is close to raw glass (float glass plate, sample 8). It is recognized that it has reflective distortion characteristics. Furthermore, as shown in FIGS. 4A to 4F, when a crack occurs in the coated glass plate of the present invention, the self-propulsion of the crack is suppressed, and many lines of breakage occur at one end of the glass plate. Since the window does not reach the other end, the risk of broken pieces of glass falling from the window can be reduced. In addition, when a glass plate breaks, the self-propulsion of the crack is suppressed so that the line of destruction does not extend from one side of the glass plate to the other, reducing the risk of broken glass pieces falling from the window. Although it is preferable, the presence of about one break line of this type is not practical because even if there is about one break line extending from one side of the glass plate to the other, there is actually little risk of broken pieces falling from the window.
This is an acceptable fracture pattern for the glass plate of the present invention. As described above, according to the present invention, the wind pressure resistance strength is practically sufficient, there is no thermal cracking, the crack does not move on its own even if the crack enters the glass plate, and the coating has less reflective distortion. A glass plate can be provided, and in particular, this coated glass plate is most suitable as a glass plate for windows and spandrels of buildings and structures such as buildings and houses. In addition, the glass plate according to the present invention has improved wind pressure strength and thermal cracking strength,
In addition, since crack self-propulsion is prevented, for example, compared to window glass plates for medium and high-rise buildings where conventionally 12 mm thick uncoated glass plates have been used, the present invention's 10
It can be used in place of a mm-thick coated glass plate, making it possible to reduce the weight of the glass plate.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of a heat treatment apparatus used to manufacture a glass plate of a comparative example, and FIG. 2 shows a schematic diagram of an example of a heat treatment apparatus used to manufacture a glass plate of the present invention. , FIG. 3 shows measurement diagrams of reflection distortion of coated glass plates according to the present invention and comparative examples, FIG. 4 shows fracture pattern diagrams of coated glass plates according to the present invention and comparative examples, and FIG. 5,6
The figure shows a measurement diagram of plane compressive stress in the peripheral areas of Samples 2 and 4. 10: Glass plate, 11: Roller hearth, 1
2: Conveyance roll, 13: Heating device, 14: First lehr, 15: Second lehr, 16: Third lehr.

Claims (1)

[Scope of Claims] 1. A coated glass plate having a thickness of 5 mm to 12 mm, a solar ray absorption rate of at least 55%, and a visible light reflectance of 10% or more, the glass plate having a thickness of 5 mm to 12 mm; Plane compressive stress is 50Kg/cm ² to 150Kg/cm ² ,
A coated glass plate characterized in that the surface compressive stress is 30Kg/cm ² to 100Kg/cm ² . 2. The coated glass plate according to claim 1, wherein the glass plate has a central tensile stress of 60 Kg/cm ² or less. 3. The coated glass plate according to claim 1, wherein the coating is a heat ray reflective coating.