WO1997008110A1

WO1997008110A1 - Glass suitable for vehicles

Info

Publication number: WO1997008110A1
Application number: PCT/JP1996/002392
Authority: WO
Inventors: Jeetendra Sehgal; Junichiro Kase; Shigeyuki Seto; Hiroshi Yamakawa; Toru Takabayashi; Akira Takada; Koichi Osada
Original assignee: Asahi Glass Company Ltd.
Priority date: 1995-08-28
Filing date: 1996-08-27
Publication date: 1997-03-06

Abstract

A glass suitable for vehicles, substantially comprising the following components and having a density of 2.45 g/cc or below at room temperature: SiO2 74 to 83 (% by weight), B2O3 0 to 5(% by weight), MgO 0 to 10 (% by weight), CaO 0 to 10 (% by weight), ZnO 0 to 10 (% by weight), Na2O + K2O + Li2O 6 to 23 (% by weight), Al2O3 0 to 5 (% by weight).

Description

Akitoda

TECHNICAL FIELD The present invention relates to glass having low density, excellent scratch resistance, and suitable for vehicles. Background Art Conventionally, as glass for vehicles, a soda lime glass usually produced by a float method has been used. Power glass is used and generally has the following composition and a density of about 2.5 g / cc.

S i 0 ₂ 6 6-7 5 (% by weight),

M g O '0-5 (% by weight),

C a O 7-: I 2 (% by weight),

N a ₂ 0 2~2 0 (wt%),

200 to 3 (% by weight),

A 1 2 0 0-4

To be used as vehicle glass, it must be suitable for use as tempered glass, curved glass, or glass with a heating element. The technical background of each aspect is described below.

Conventionally, tempered glass has been used for vehicles, buildings, etc., and has been used as a glass that has improved the disadvantage of being easily broken. Tempered glass is made by a heat strengthening method in which a glass sheet manufactured by the float method is heated to a temperature close to the softening point, and then the surface is blown with air to rapidly cool.

In this method, the heat shrinkage during cooling is used, and the surface first cools and shrinks, and then the inside shrinks, so that compressive stress remains on the glass surface and the strength of the glass improves. In addition, from the viewpoint of abrasion resistance, the tempered glass has an effect of suppressing the progress of scratches since compressive stress remains on the surface, and has an effect of improving scratch resistance. Since tempered glass for vehicles and buildings is used facing the outdoors, it is used in an environment where dust from wind and rain is constantly applied. For this reason, even if reinforced, the surface was easily scratched, and there was a risk that visibility would deteriorate over time and damage caused by the scratches would occur. If the reinforcement is too strong, the abrasion resistance is improved, but the stress inside the glass is too large and there is a disadvantage that the glass is easily broken by a slight impact. In other words, the improvement in scratch resistance relying solely on heat strengthening has reached its limit.

When glass was used for high-rise buildings and vehicles, there was also a problem that the weight of the glass itself became considerably heavy. There was no substantial improvement in the weight reduction of the glass, and the reduction in the thickness of the glass reduced the weight. In addition, since tempered glass is strengthened by utilizing the temperature difference between the surface and the interior when the glass is cooled, it is difficult for glass with a size of 2.8 mm or less to be essentially strengthened, and the tempered glass is lightened by thinning. The transformation was reaching its limits.

From compositional knowledge, it is known that in soda lime silica glass, increasing the content of silica increases hardness, but simply increasing the content of silica lowers the coefficient of thermal expansion, making it a tempered glass. Was unsuitable. Further, B ₂ 0 and ₃ 1 0% or more including Houkei silicate glass is used, such as the physical and chemical equipment, density rather low, is known as crack-resistant glass, the thermal expansion coefficient of these glasses small fence However, it could not be used as tempered glass.

In other words, it was generally accepted that it is difficult to strengthen glass having high scratch resistance because the improvement of scratch resistance and the strength of tempering are contradictory. Conventionally, bent glass has been used for vehicles and buildings, and has been used to create beautiful appearance as part of the design of cars and buildings. Bent glass is manufactured by increasing the temperature of a glass sheet manufactured by the float method to a temperature above the strain point and near the softening point, and mechanically applying stress or using bending due to gravity. ing.

The strain point, viscosity 1 0 "- ⁵ Boyes in viscosity curve of the glass, in the softening point is the temperature at the viscosity becomes 1 0 ^{^7.6} Boyes. Above the softening point temperature, Ru good the weight of glass It is not suitable for bending because the deformation becomes severe and the basic shape of the plate collapses. No. At temperatures below the strain point, bending cannot be performed because viscous flow of glass does not occur. In actuality, due to the stability of production, bending is performed in the temperature range where the viscosity is 10 ^β · ⁵ to 10 ”· ⁵ .

Curved glass for vehicles and buildings is used outdoors, so it is used in an environment where dust from wind and rain is constantly applied. For this reason, the surface was easily scratched, and there was a possibility that visibility might be deteriorated or damage due to the scratch might be caused over a long period of time. In particular, windshields of passenger cars and railway vehicles are hit by pebbles and sand at high speeds while driving, and in snowfall areas, dust from road surfaces cut by spike tires, chains, etc. is added to this. Furthermore, the surface was easily scratched due to the extremely severe situation of being rubbed by the wiper. In other words, there has been a strong demand for improved abrasion resistance of curved glass.

From the compositional findings mentioned above, it is known that in soda-lime silica glass, increasing the silica content increases the hardness, but simply increasing the silica content increases the bending temperature. However, it is not suitable as glass for vehicles or buildings where productivity is required.

From the viewpoint of manufacturing, bending requires processing at a temperature of 108 to ⁵ boise to 10 " ^5. This is because conventional soda-lime silica glass

In the bending process, an external force must be applied at a high temperature while maintaining the specified temperature accurately, which reduces the simplicity of work, safety, and manufacturing costs. From a viewpoint, it is rather required to lower the working temperature.

That is, the improvement of scratch resistance and the stiffness of bending are practically contradictory properties, and it has been difficult to bend glass with high scratch resistance.

Further, in the past, as a rear glass for passenger cars and the like, glass provided with an electric heating element for removing fogging has been often used. However, these glasses usually have the problem that it takes a few minutes to over a dozen minutes to remove the assault on the entire fogged glass surface and restore the rear view. On the ground, the frost was frozen on the outside of the glass, and it took a longer time to remove the frost. For this reason, it has been desired to reduce the time required for removing cloudiness and frost as much as possible.

To increase the heating value of the electric heating element to improve the ability to remove fogging and frost 97/08110

Four

However, in this case, the power consumption increases and the battery becomes burdensome, the temperature near the heating element becomes high, and the temperature difference between the heating element and other parts increases. However, there is a problem that a large thermal stress inside the glass may lead to breakage.

In addition, it is conceivable to reduce the interval between the heating elements.However, in this case, the overall length of the heating elements becomes longer, which not only increases the power consumption, but also obstructs the rear view itself due to the heating interruption. is there.

The present invention solves the above-mentioned problems, and provides a glass suitable for vehicles that has excellent scratch resistance and is useful as tempered glass, curved glass, and glass with an electric heating element. DISCLOSURE OF THE INVENTION The present invention is a glass suitable for vehicles having a composition at room temperature and a density at room temperature of 2.45 gZcc or less.

S i 0 ₂ 74-83 (% by weight),

B _{20 a} 0-5 (% by weight),

MgO 0 10 (% by weight),

C aO 0 10 (% by weight),

ZnO 0 10 (% by weight),

N a ₂₀ + K ₂₀ + L i 0 623 (% by weight),

A 1 ₂ 0 ₃ 0 5 (wt%) BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an explanatory diagram for explaining the definition of the fragility of the present invention.

FIG. 2 is a graph showing the relationship between the cooling rate and the brittleness index value of the glass of the present invention and the conventional glass.

Fig. 3 is a conceptual diagram of the mold frame used for bending. BEST MODE FOR CARRYING OUT THE INVENTION In one aspect of the present invention, in the composition region close to the conventional soda lime silica glass, the density of the glass is such that the method of crack propagation when the glass breaks. Is based on the finding that it governs In other words, in a specific composition range, glass with a density of 2.45 / cc or less has a high breaking strength due to crack extension, resulting in a high strength of the glass itself, and is equivalent to soda-lime silica glass. By using this as tempered glass, the number of cracks that extend on the surface layer under friction or impact can be reduced, and the scratch resistance can be dramatically improved. Such glass also has high bending workability.

In the present invention, the brittleness index value B proposed by Lohn et al. Is used as an index of the crack extension of glass (BR Lawn and DB Marshall, J. Am. Cerani. Soc., 62 [ 7-8] 347-350 (1979)). Here, fragility index value B (Unit: m - ^1/2) is defined by equation (1) from Bidzukasu hardness H v and fracture toughness value K _c of the material.

Major problem in applying an indication of the fragility in glass fracture toughness value K _e is that difficult to evaluate accurately. Therefore, the present inventor studied several techniques and found that the brittleness was determined from the relationship between the size of the trace of the indenter remaining on the glass surface when the Vickers indenter was pushed in and the length of the cracks generated from the four corners of the trace. We found that it can be quantitatively evaluated. The relationship is defined by equation (2).

c / a = 0. 0 0 5 6 B ^2/3 P ¹ no ⁶ (2)

Here, P is the indentation load (unit: N) of the Vickers indenter, and a and c are the diagonal length of the Vickers indentation and the length of the crack generated from the four corners, respectively, as shown in Fig. 1. (Total length of two symmetric cracks including indenter marks).

By using the dimensions of the Vickers indentation on the surface of each glass and the equation (2), it is possible to easily evaluate the extension of glass cracks. A small brittleness index value means that cracks do not easily propagate, and has excellent scratch resistance and strength. It becomes the evaluation standard of glass.

According to the present invention, a glass which is lightweight, has excellent scratch resistance, and is suitable for vehicles can be obtained by setting the density at room temperature to 2.45 c or less within a predetermined composition range. In the glass of the present invention, a preferable brittleness index value is 6000 m_1 ^{/ 2} or less, more preferably 5500πι · ^{1 / !!} or less. Since the brittleness index value decreases as the density decreases, the density is set to 2.45 gZcc or less. Since the brittleness index value changes more rapidly particularly around the density of 2.41-2.43 gZc c, the density is preferably 2.43 g / cc or less.

To maintain the proper density, as a composition component of the glass of the present invention, S i 0 ₂ is the 7 4-83 wt%, B ₂ 0 ₃ is not essential to 0-5 wt%.

In the present invention, the content of B ₂ 0 ₃ is in the up to 5% by weight. If it exceeds 5% by weight, the life of the kiln may be shortened due to scattering of boric acid during melting. Furthermore, mechanical properties such as thermal expansion are different from soda-lime silica glass, making it difficult to simply apply the same equipment as soda-lime silica glass to manufacture. In particular, when used as tempered glass, it is difficult to maintain a large coefficient of thermal expansion, and it may not be suitable for tempering.

Glass that contains B ₂ 0 ₃ maintains a low brittleness index value to a higher density. From this point of view, it contains B ₂ Oa in an amount of 0.5 (wt%) or more, or B ₂ O ₃ in an amount of 0 to less than 0.5 (wt%) and a density of 2.43 gZcc or less. It is preferable that the glass be 2.41 gZcc or less. In the latter containing the B ₂ 0 ₃ it is not essential.

In the present invention, “essentially” means that other components can be added as long as the effects of the present invention are exhibited. The other ingredients, additives or for homogenization of the glass, ultraviolet light, in which the visible light is added as a colorant, and a clarifying agent for the transmittance control of the infrared light, Fe ₂ 0 ₃ _{, Co0, NiO, Ce0 2,} T i 0 2, V 2 0 5, C r 2 0 3, Sn0 2, Se, S0 3, N0 3, As 2 0 3, S b 2 0 3, F, C 1 And the like.

Hereinafter, preferred embodiments of the tempered glass plate, the curved glass plate, and the glass plate with an electric heater will be described. [Tempered glass plate]

The tempered glass sheet referred to in the present invention is a tempered glass sheet using heat shrinkage of glass called heat strengthening or physical strengthening, and is used for windows of vehicles such as passenger cars, trucks, buses, railways, ships, and aircraft. Tempered glass plates used for headlights and taillights, tempered glass plates used for construction such as windows of buildings and houses, doors, show windows, etc.Furniture and office supplies such as partitions, desktops, bookshelves, showcases, etc. Tempered glass plate used for home appliances and tempered glass plate used for home appliances such as cooking utensils.

Particularly preferred as a strengthened glass plate using the glass of the present invention are as follows.

That has essentially the following composition, and a thermal expansion coefficient of 50 to 300 is 80 <10_ ⁷ or hand, the glass plate is less than density 2. 45 gcc at room temperature, heating, and quenching It is a strong glass plate strengthened by this.

S i 0 ₂ 74-83 (% by weight),

B ₂ 0 ₃ 0 to 5 (% by weight),

S i 0 ₂ B ₂ 0 74-83 (% by weight),

MgO 0-10 (wt%),

C aO 0-; I 0 (% by weight),

ZnO 0-; I 0 (% by weight),

N a ₂ O + KO + L i 20 12 to 23 (% by weight),

A 1 ₂ 0 ₃ 0~ 5 (wt%) o

In conventional soda lime glass, the brittleness index value is 6800 to 7400 m_l ^{/ 2} , and by strengthening this, the tempered glass with the brittleness index value of 5000 to 6000 m- ^{l / 2} can be obtained. can get. However, when the Vickers indenter is pressed into the tempered glass, it is difficult to measure accurately because the stress on the glass surface causes the damage to be not always steady. Therefore, in the following, the brittleness index value of the mother glass before tempering is mainly used.

To maintain the proper density and thermal expansion _{_{coefficient, S i 0 2, B 2}} Oa is in total, and 74 to 83 wt%. MgO, CaO, and ZnO are not essential, but can be contained in an amount of 10% by weight or less to improve chemical durability. Although A l ₂ 0 not ₃ also essential, to enhance the I匕学durability can contain 5 wt% or less.

In addition, in order to perform effective thermal strengthening, glass having a thermal expansion coefficient <2 at a temperature of 50 to 300 <8010_ or more is thermally strengthened. In viewpoint of a relatively large α thermal expansion coefficient, as the composition of the glass, the total amount of _{_{Na 2 0, K 2 0,}} L i 2 0 and 12 to 23 (wt%). Preferably, it is 14 to 23 (% by weight).

The tempered glass sheet of the present invention is effective not only for increasing the resistance to scratches and impacts, but also for reducing the weight of the glass because of its low density.

The B ₂ 0 ₃ 0~0. 5 when using the glass containing less than (% by weight) in the tempered glass of the present invention, in order to sufficiently low brittleness index value B, and in 50 to 300 ^e C the thermal expansion coefficient α to a 80 X 10_ ⁷ / 'C or higher, in the range, essentially, it is preferable that the glass having the following ingredients.

S i 0 ₂ 75.5 to 83 (% by weight),

RO 1 ~ 8 (wt%),

R _'2 0 14~23 (wt%),

R0 + R _'2 0 15~24 (wt%),

A 12 0 ₃ 0~ 5 (wt%),

RO / R _'2 0 (by weight) 0.5 or less.

Here, R is at least one selected from Mg, Ca, and Zn, and R 'is at least one selected from Li, Na, and K.

Here, contain RO 1 wt% or more is to secure the durability of the water resistance, R0 / R _'2 0 are we (weight ratio) 0.5 or less, brittleness This is to reduce the index value sufficiently.

In particular, in the above range, the following glasses are preferred.

S i 0 ₂ 75.5 to 83 (% by weight),

M O 0-8 (% by weight),

C a 0 0 to 8 (% by weight),

ZnO 0-8 (wt%), RO 1 ~ 8 (wt%),

N a _{200 to} 23 (% by weight),

K ₂ 0-10 (% by weight),

L i 200-: I 0 (% by weight),

R _'2 0 14~23 (wt%),

A 12 0 ₃ 0. 5~ 5 (wt%).

Here, contains A 1 ₂ 0 ₃ 0 5 wt% or more is a order to further improve the durability of the water resistance

Further, B ₂ 0 ₃ and 0.5 5 (wt%) a glass containing in using the tempered glass of the present invention, in order to sufficiently lower the brittleness index value, and at 50 to 300 ^e C to the α coefficient of thermal expansion 8 O x 1 0_ ⁷ Roh above, in the above range, essentially, it is preferable that the glass having the following ingredients.

S i 0 ₈ 74-83 (% by weight),

B ₂ 0 ₃ 0.5 to 5 (% by weight),

S i 0 ₂ + B 0 75.5 to 83 (% by weight),

RO 1-9 (wt%),

R _'2 0 14~23 (wt%),

RO + R'zO 1 5 to 24 (% by weight),

A 12 Oa 0-5 (% by weight),

R0ZR _'2 0 (weight ratio) 0.6 or less ₀

Here, what contains R0 1 wt% or more, to ensure the durability of the water resistance, R0 / R _'2 0 are we (weight ratio) 0.6 or less, brittleness This is to reduce the index value sufficiently.

In particular, in the above range, the following glasses are preferred.

S i 0 ₂ 74-83 (% by weight),

B ₂ 0 ₃ 0.5 to 5 (% by weight),

S i 0 ₂ + B ₂ 0 ₃ 75.5 to 83 (% by weight), MgO 9 (% by weight),

C aO 0 9 (% by weight),

ZnO 9 (% by weight),

RO 9 (% by weight),

Na ₂ 0 0 1 22 (% by weight),

K ₂ 0-10 (% by weight),

L i 200 to 10 (% by weight),

R _'2 0 14~23 (wt%),

RO + R 0 15-24 (% by weight),

A120.0 0.5-5 (% by weight).

Here, contains A 1 ₂ 0 ₃ 0. 5 wt% or more, in order to improve the durability such as water resistance.

In order to examine the performance of the tempered glass plate of the present invention, a small sample piece was prepared and evaluated. That is, after 200 g of the raw material powder of each composition was put into a crucible made of platinum, it was heated and melted with stirring for 4 hours in the atmosphere of 1450-1650. The uniformly melted glass of each composition was poured into a carbon mold, formed into a plate of about 10 cm square and 5 mm thick, and cooled. The resulting glass was annealed at 490-570 to remove distortion, then cut and polished to obtain a 4 mm thick sample.

The mirror-polished sample is heated to a temperature slightly higher than the glass distortion temperature in 1 OO ^ Z hours, then held for 3 hours, and gradually reduced to 60 / hour to remove the surface stress due to polishing. It was cooled and used as a sample for evaluation as a glass plate before tempering. For the evaluation of the tempered glass plate, a sample that was blown with air and quenched at about 500 * C / minute was used.

The brittleness index B was evaluated for the specimen from which the surface stress was removed by polishing. The abrasion resistance of the test piece from which surface stress was removed by polishing and the test piece after strengthening were evaluated by the amount of wear by sandblasting. That is, by converting the amount of abrasion of the sandblasting at a pressure 1 kf / cm ² in a circular area with a diameter of 2 cm of material 2 minutes from the weight reduction of the line Le ,, material. D1 is the abrasion of the glass before tempering and D2 is the abrasion of the glass after tempering. D2 was measured for only some of the samples. The density P at room temperature was calculated from the dry weight of the sample and the weight in water by the Archimedes method.

Tables 1 and 2 show the composition (% by weight) of the glass used, the density at room temperature P (g / cc), the brittleness index B (m- ^{1 / 2} ) and the amount of wear D 1 (μηι), D 2 (urn), and coefficient of thermal expansion α (X 10 "V ^e C) at 50 to 300 * C in the sand blast test. an example of the tempered glass of the invention, examples 19 to 37 is, except for that. example 37 Comparative example could formed shapes by melt. also, if the 51 +8 510 ₂ and beta ₂ 0 ₃ Blank indicates that no measurement was taken.

As shown in the results of the sand blast test in the table, in the glasses obtained in Examples 1 to 18, the wear amount D 1 of the glass before tempering was 24 or less, and the scratch resistance was excellent. The amount of wear D2 when a part of the glass is quenched and strengthened by blowing air is, for example, 17 / xm or less, and it is recognized that the scratch resistance is further improved. It is presumed that the tempered glass of the present invention satisfies the specifications of JIS R3206, JIS R3211, and JIS R3212.

In Examples 19 to 26, the thermal expansion coefficient α was 80 ^× 10 ^{Τ Τ}以下, and it was difficult to strengthen the heat when it was below. Even if quenching was performed by blowing air, no improvement in scratch resistance was observed. In Examples 27 to 36, the abrasion loss D2 was 20 m or more even after strengthening, and the scratch resistance was lower than that of the glass of the present invention.

FIG. 2 shows the relationship between the cooling rate and the brittleness index value of the conventional soda-lime silica glass (Example 27) and the glass of Example 1 of the present invention. In the figure, black circles indicate conventional soda lime glass, and white circles indicate glass of the present invention. From the figure, it can be seen that the faster the cooling rate, the stronger the condition. Normal tempered glass is cooled at a very fast cooling rate of about 40 ocrcz by blowing air. Here, cooling was performed at l ~ 50 ^e CZ, which can be controlled by an electric furnace. The tempered glass according to the present invention exhibits scratch resistance equal to or higher than that of conventional tempered glass even in a state where it is hardened almost completely, and the scratch resistance is further improved by strengthening. Example Si02 B203 MRO CaO ZnO Na20 20 Li 20 A 1203 RO R '20 RO + R' 20 RO / R '20 Si + BB

1 77.6 0.0 2.7 0.9 0.0 13.6 1.7 0.0 3.4 3.6 15.3 18.9 0.24 77.6 2.395 51

2 77.3 0.0 1.7 2.3 0.0 15.2 0.0 0.0 3.4 4.0 15.2 19.2 0.26 77.3 2.407 57

3 77.6 0.0 2.7 0.9 0.0 15.3 0.0 0.0 3.4 3.6 15.3 18.9 0.24 77.6 2.395 50

4 77.8 0.0 3.3 0.0 0.0 15.3 0.0 0.0 3.4 3.3 15.3 18.6 0.22 77.8 2.386 48

5 77.1 0.0 4.0 0.0 0.0 14.3 2.6 0.0 2.0 4.0 16.9 20.9 0.24 77.1 2.400 52

6 76.9 0.5 1.7 2.3 0.0 15.2 0.0 0.0 3.4 4.0 15.2 19.2 0.26 77.4 2.413 59

7 76.8 1.0 2.3 0.0 1.0 15.3 0.0 0.0 3.4 3.3 15.3 18.6 0.22 77.8 2.398 51

8 75.8 1.5 2.7 0.9 0.0 15.2 0.0 0.0 3.9 3.6 15.2 18.8 0.24 77.3 2.420 58

9 76.1 1.5 2.7 0.9 0.0 13.6 1.7 0.0 3.4 3.6 15.3 18.9 0.24 77.6 2.409 48

10 77.0 1.5 1.0 3.0 0.0 12.5 4.0 0.0 1.0 4.0 16.5 20.5 0.24 78.5 2.424 52

11 77.0 1.5 1.0 4.0 0.0 11.5 4.0 0.0 1.0 5.0 15.5 20.5 0.32 78.5 2.428 50

12 77.0 1.5 4.0 0.0 0.0 12.5 4.0 0.0 1.0 4.0 16.5 20.5 0.24 78.5 2.417 52

13 77.0 1.5 5.0 0.0 0.0 11.5 4.0 0.0 1.0 5.0 15.5 20.5 0.32 78.5 2.419 57

14 75.6 2.5 4.0 0.0 0.0 14.3 1.0 0.0 2.6 4.0 15.3 19.3 0.26 78.1 2.420 58

15 79.9 0.0 0.0 4.7 0.0 15.2 0.0 0.0 0.0 4.7 15.2 19.9 0.31 79.9 2.410 58

16 76.8 0.0 0.0 4.6 0.0 13.1 2.0 0.0 3.4 4.6 15.1 19.7 0.30 76.8 2.421 63

17 77.0 0.0 8.5 0.0 0.0 0.0 6.0 8.5 0.0 8.5 14.5 23.0 0.59 77.0 2.405 57

18 77.5 0.0 8.5 0.0 0.0 0.0 7.0 7.0 0.0 8.5 14.0 22.5 0.61 77.5 2.400 58

Example Si 02 B203 MgO CaO ZnO Na20 K20 Li20 A 1203 RO R'20 RO + R '20 RO / R' 20 Si + B 0 B

19 77.0 1.5 1.0 6.0 0.0 10.0 3.5 0.0 1.0 7.0 13.5 20.5 0.52 78.5 2.430 490

20 83.0 0.0 3.3 0.0 0.0 10.1 0.0 0.0 3.4 3.3 10.1 13.4 0.33 83.0 2.347 400

21 81.5 1.5 3.3 0.0 0.0 10.1 0.0 0.0 3.6 3.3 10.1 13.4 0.33 83.0 2.366 570

22 85.0 0.0 3.3 0.0 0.0 8.1 0.0 0.0 3.4 3.3 8.1 11.4 0.41 85.0 2.329 350

23 78.0 0.0 9.5 0.0 0.0 0.0 7.5 5.0 0.0 9.5 12.5 22.0 0.76 78.0 2.397 500

24 80.3 0.0 0.0 9.4 0.0 10.2 0.0 0.0 0.0 9.4 10.2 19.6 0.92 80.3 2.431 610

25 75.5 6.0 0.0 8.2 0.0 10.3 0.0 0.0 0.0 8.2 10.3 18.5 0.80 81.5 2.520 690

26 69.6 6.5 0.0 4.8 0.0 9.2 0.0 0.0 9.9 4.8 9.2 14.0 0.52 76.1 2.480 620

27 73.0 0.0 3.7 7.8 0.0 13.0 0.7 0.0 1.7 11.5 13.7 25.2 0.84 73.0 2.486 710

28 75.5 0.0 0.0 14.1 0.0 10.1 0.0 0.0 0.0 14.1 10.1 24.2 1.40 75.5 2.509 6700

29 70.0 0.0 0.0 9.3 0.0 20.4 0.0 0.0 0.0 9.3 20.4 29.7 0.46 70.0 2.520 7000

30 74.8 0.0 0.0 4.7 0.0 20.3 0.0 0.0 0.0 4.7 20.3 25.0 0.23 74.8 2.460 6100

31 69.6 0.0 0.0 4.8 0.0 15.7 0.0 0.0 9.9 4.8 15.7 20.5 0.31 69.6 2.461 6300

32 58.9 0.0 0.0 4.8 0.0 16.0 0.0 0.0 20.2 4.8 16.0 20.8 0.30 58.9 2.488 6200

33 47.4 0.0 0.0 4.9 0.0 16.0 0.0 0.0 31.3 4.9 16.0 20.9 0.31 47.4 2.532 6600

34 75.1 0.0 0.0 9.4 0.0 15.2 0.0 0.0 0.0 9.4 15.2 24.6 0.62 75.1 2.480 6500

35 70.7 6.1 0.0 9.7 0.0 13.5 0.0 0.0 .0.0 9.7 13.5 23.2 0.72 76.8 2.550 7200

36 74.8 5.5 0.0 4.9 0.0 14.8 0.0 0.0 0.0 4.9 14.8 19.7 0.33 80.3 2.500 6800

37 88.0 0.0 0.0 2.0 0.0 7.0 0.0 0.0 3.0 2.0 7.0 9.0 0.29 88.0

[Curved glass plate]

The curved glass sheet referred to in the present invention is a curved glass sheet manufactured by increasing the temperature of a sheet glass to a temperature equal to or higher than a strain point and near a softening point temperature, mechanically applying stress, or utilizing deflection caused by gravity. Curved glass used for windows, headlights, and taillights of vehicles such as cars, trucks, buses, railways, ships, and aircraft, and curved glass used for buildings, houses, windows, doors, and show windows A curved glass plate used for furniture such as plates, partitions, bookshelves, and showcases, and office supplies.

Preferred as a curved glass plate using the glass of the present invention are as follows.

In other words, it is a curved glass sheet that is formed by heating and softening a glass sheet having the following composition and a density at room temperature of 2.45 gZcc or less.

S i 0 ₂ 74-80 (% by weight),

B ₂ 0 ₃ 0 to 5 (% by weight),

Mg 0-10 (% by weight),

CaO 0-10 (% by weight),

ZnO 0-; I 0 (% by weight),

N a ₂₀ + K ₂₀ + L 0 10 to 23 (% by weight),

A 12 0 ₃ 0~ 5 (wt%).

The brittleness index of conventional soda-lime glass is 6800 to 7400 m- ^{1 / z} , and this value is the same for both flat glass and curved glass if the surface distortion is removed. The values are almost the same. However, in measurements where the Vickers indenter is pushed into a curved glass plate with a large curvature, scratches on the glass surface do not grow constantly, making accurate measurement difficult. Therefore, in the following, the brittleness index value of the sheet glass before bending is basically used.

To maintain moldability and bending appropriate density, and the composition component of the curved glass plate of the present invention, S i 0 ₂ is set to 74-80% by weight.

MgO, CaO, and ZnO are not essential, but enhance chemical durability. Therefore, it can be contained up to 10% by weight. Although A l ₂ 0 not ₃ also essential, to enhance the I numerology durability, can contain 5 wt% or less.

To a bending easier, curved glass plate of the present invention as a composition _{_{component, Na 2 0, K 2 0}} , L i 2 0 which contained 10 to 23 wt% in total.

In particular, the bending in order to perform the machining easily, viscosity 10 ^{^8.5} temperature at 70 0 below the Boise, preferred that the viscosity temperature at which 10 ^1, ⁵ Boyes is 520 or less arbitrarily.

The curved glass plate of the present invention is effective not only for increasing the resistance to scratches and impacts, but also for reducing the weight of the glass because of its low density.

Beta ₂ 0 ₃ and 0 to 0.5 when using a glass containing less than (% by weight) in the curved glass plate of the present invention, in order to sufficiently lower the brittleness index value, in the range, essentially Preferably, the glass has the following components.

S i 0 ₂ 75.5 to 80 (% by weight),

RO 1 ~ 8 (wt%),

R _'2 0 1 0~23 (wt%),

RO + R'iO 1 1 ~ 24 (wt%),

A 1 ₂ 0 ₃ 0~ 5 (wt%),

R0 / R _'2 0 (by weight) 0.5 or less.

Here, what contains R0 1 wt% or more, to ensure the durability of the water resistance, R0ZR _'2 0 are we (weight ratio) 0.5 or less, brittleness index value Is set to be sufficiently low.

In particular, in the above range, the following glasses are preferred.

S i 0 ₂ 75.5 to 80 (% by weight),

MgO 0-8 (wt%),

C aO 0-8 (% by weight),

ZnO 0-8 (wt%),

R 0 1 ~ 8 (% by weight), O 97/08110

16

N a _{200 to} 23 (% by weight),

K ₂ 0-10 (% by weight),

L i a 0 to 10 (% by weight),

R _'z 0 10~23 (wt%),

R0 + R 0 1 1 to 24 (% by weight),

A 1 ₂ 0 0.5 to 5 (% by weight),

R0 / R _'2 0 (by weight) 0.5 or less.

Here, contains A l ₂ 0 ₃ 0. 5 wt% or more, in order to improve the durability such as water resistance.

Further, when using a glass containing B ₂ 0 ₃ and 0.5 to 5 (wt%) to the curved glass plate of the present invention, in order to sufficiently lower the brittleness index value, in the range, essentially Preferably, the glass has the following components.

S i 0 ₂ 74-80 (% by weight),

B ₂ 0 ₃ 0.5 to 5 (% by weight),

S i Oz B ₂ 0 75.5 to 85 (% by weight),

RO 1-9 (wt%),

R _'2 0 10~23 (wt%),

R 0 + R ' ₂ 0 1 1 to 24 (% by weight),

A 1 ₂ 0 ₃ 0~ 5 (wt%),

R0 / R _'2 0 (weight ratio) 0.6 or less.

Here, what contains R0 1 wt% or more, to ensure the durability of the water resistance, R0ZR _'2 0 are we (weight ratio) 0.6 or less, brittleness index value Is set to be sufficiently low.

In particular, in the above range, the following glasses are preferred.

S i z 74-80 (% by weight),

B ₂ Oa 0.5 to 5 (% by weight),

S i 0 ₂ + B ₂ 0 ₃ 75.5 to 85 (% by weight), MgO 0-9 (wt%),

C a 0 0 to 9 (% by weight),

ZnO 0-9 (wt%),

RO 1-9 (wt%),

N a ₂₀ o to 23 m%),

_Kz 0-10 (% by weight),

L i _{200 to} 10 (% by weight),

R _'2 0 10~23 (wt%),

RO + R: 0 1 1 to 24 (% by weight),

_{_{A 1 2 0 3 0 5~ 5}} ( wt%),

R0 / R _'2 0 (weight ratio) 0.6 or less.

In order to investigate the performance of the curved glass plate of the present invention, a small sample piece was prepared and evaluated. That is, 200 g of the raw material powder of each composition was put into a crucible made of platinum, and then heated and dissolved in an atmosphere of 1450-1650'C while stirring for 4 hours. The uniformly melted glass of each composition was poured into a carbon mold, formed into a plate of about 10 cm square and 5 mm thick, and cooled. The obtained glass was annealed at a temperature slightly higher than the temperature at which the viscosity became 10 " ^s and the strain was removed, then cut and polished to obtain a 4 mm thick sample.

The sample that has been polished to give a mirror surface is heated again at a rate of 100 / hour to a temperature slightly higher than the viscosity at which the viscosity becomes 10 "· ⁵ Vois, and then held for 3 hours in order to further remove the surface stress due to polishing. , 6 (Slowly cooled at TC time to obtain a sample for evaluation.

The evaluation of the curved glass plate, the glass plate was placed on the radius of curvature 30 on the stainless steel of the type curved concave in cm, viscosity and heated to a temperature of 10 ^{^8.5} Boyes, same curvature from the top side A curved glass was created by pressing a stainless steel mold that was curved into a convex shape. The obtained glass was annealed at a temperature slightly higher than the temperature at which the viscosity became 10 ″ · ⁵ boise to remove the distortion.

In this way, a flat specimen with the surface stress removed by polishing and a test after bending The brittleness index B was evaluated for the specimen. B1 is a brittleness index value before bending, and B2 is a brittleness index value after bending. B2 was measured for only some of the sample pieces.

In addition, the abrasion resistance of the flat specimen was evaluated by the amount of abrasion caused by sandblasting. That is, sand blasting was performed for 2 minutes at a pressure of 1 kgfZcm ² on a circular region having a diameter of 2 cm of the material, and the wear amount D was calculated from the weight loss of the material.

The density P at room temperature was calculated by the Archimedes method from the dry weight of the sample and the weight in water.

As Examples and Comparative Examples of the present invention, Tables 3 and 4 show the composition (weight%) of the glass used, the density P (g / cc) at room temperature, and the brittleness index value B 1 (m- ¹ ^{^{2), B 2 (m- 1}} /2) and wear amount in the sandblasting test D (μπι), the temperature showing a 10 ^{^8.5} Boyes _{_{Τ β. 5 (), 10}} ' the temperature T "indicating a ^{4 5} Boyes. ₅ (.C) Examples 38 to 56 are working examples of the curved glass plate of the present invention, and Examples 57 to 74 are comparative examples. , 51 + 8 shows the total amount of 510 ₂ and the B ₂ 0 _3. the blank was not measured.

As shown in the brittleness index values in the table and the results of the sandplast test, in the glasses obtained in Examples 38 to 56, the brittleness index value B of the glass plate was 6000 m—i ^{/ 2} or less, and And D were 24 m or less, and the scratch resistance was good. The value of B hardly changed before and after bending.

In Example 57-60, B is at 6000Paiganma ¹ Bruno ² below, D is a less 24 mu m, although the abrasion resistance is excellent, the temperature at which the viscosity becomes 1 0 ^{^8.5} Boyes over 700, or, Since the temperature at which the viscosity becomes 10 "· ⁵ voids is 520 * 0 or more, higher temperatures are required for bending, making it difficult to use for curved glass sheets.

In Examples 61 to 73, D was 25 wm or more, or B was 6100 m — ^1/2 or more, and the scratch resistance was lower than that of the glass of the present invention.

Glass having the composition of Example 38 in Table 3 was melted and formed into a plate having a width of about 35 cm, a length of about 100 cm, and a thickness of 3 mm. The obtained glass plate was placed on a stainless steel frame mold with a radius of curvature of 100 cm (Fig. 3), and the temperature was raised to 600 ° C in 10 minutes, and then to 420 at 100 ^eC / min. Cool. During this time, the glass plate was bent by its own weight and deformed into a shape following the stainless steel frame. The glass plate remains in 6 CTC hours It was gradually cooled to room temperature to obtain a curved glass plate. When a curved glass plate was examined using a polarizing plate, compressive stress was found near the edge and tensile stress was found inside, but no particularly strained portion was found near the center. .

Si02 B203 gO CaO ZnO Na20 20 Li 20 A 1203 RO R '20 RO + R' 20 RO / R '20 Si + B 0 B

38 77.6 0.0 2.7 0.9 0.0 13.6 1.7 0.0 3.4 3.6 15.3 18.9 0.24 77.6 2.395 51

39 77.3 0.0 1.7 2.3 0.0 15.2 0.0 0.0 3.4 4.0 15.2 19.2 0.26 77.3 2.407 57

40 77.6 0.0 2.7 0.9 0.0 15.3 0.0 0.0 3.4 3.6 15.3 18.9 0.24 77.6 2.395 50

41 77.8 0.0 3.3 0.0 0.0 15.3 0.0 0.0 3.4 3.3 15.3 18.6 0.22 77.8 2.386 48

42 77.1 0.0 4.0 0.0 0.0 14.3 2.6 0.0 2.0 4.0 16.9 20.9 0.24 77.1 2.400 52

43 76.9 0.5 1.7 2.3 0.0 15.2 0.0 0.0 3.4 4.0 15.2 19.2 0.26 77.4 2.413 59

44 76.8 1.0 2.3 0.0 1.0 15.3 0.0 0.0 3.4 3.3 15.3 18.6 0.22 77.8 2.398 51

45 75.8 1.5 2.7 0.9 0.0 15.2 0.0 0.0 3.9 3.6 15.2 18.8 0.24 77.3 2.420 58

46 76.1 1.5 2.7 0.9 0.0 13.6 1.7 0.0 3.4 3.6 15.3 18.9 0.24 77.6 2.409 48

47 77.0 1.5 1.0 3.0 0.0 12.5 4.0 0.0 1.0 4.0 16.5 20.5 0.24 78.5 2.424 52

48 77.0 1.5 1.0 4.0 0.0 11.5 4.0 0.0 1.0 5.0 15.5 20.5 0.32 78.5 2.428 50

49 77.0 1.5 4.0 0.0 0.0 12.5 4.0 0.0 1.0 4.0 16.5 20.5 0.24 78.5 Z.417 52

50 77.0 1.5 5.0 0.0 0.0 11.5 4.0 0.0 1.0 5.0 15.5 20.5 0.32 78.5 2.419 57

51 75.6 2.5 4.0 0.0 0.0 14.3 1.0 0.0 2.6 4.0 15.3 19.3 0.26 78.1 2.420 58

52 79.9 0.0 0.0 4.7 0.0 15.2 0.0 0.0 0.0 4.7 15.2 19.9 0.31 79.9 2.410 580

53 76.8 0.0 0.0 4.6 0.0 13.1 2.0 0.0 3.4 4.6 15.1 19.7 0.30 76.8 2.421 600

54 77.0 0.0 8.5 0.0 0.0 0.0 6.0 8.5 0.0 8.5 14.5 23.0 0.59 77.0 2.405 570

55 77.5 0.0 8.5 0.0 0.0 0.0 7.0 7.0 0.0 8.5 14.0 22.5 0.61 77.5 2.400 580

56 78.0 0.0 9.5 0.0 0.0 0.0 7.5 5.0 0.0 9.5 12.5 22.0 0.76 78.0 2.397 500

IS

Z6 £ Z0 / 96dT / XDd 0II80 / .6 O [Glass plate with electric heating element]

Preferred examples of the electrically heated glass plate using the glass of the present invention are as follows.

That is, at least the surface is essentially composed of the following composition, and the electrical conductivity is provided on the surface of a glass plate having a thermal conductivity of at least room temperature (0. It is a glass plate with an electric heating element.

S i 0 ₂ + B ₂ 0 ₃ 75-86 (% by weight),

However, B ₂ 0 ₃ 0 to 5 (% by weight),

MgO + CaO + ZnO 2 ~ 10 (wt%),

_{_{Na 2 0 + K 2 O +}} L i 2 0 6~20 ( wt%),

A 12 0 ₃ 0~ 5 (wt%).

S i O 2 and B ₂ 0 ₃ is Ru component der serving as a network former of glass. If the total amount is less than 75% by weight, the thermal conductivity will not be sufficiently high. If it exceeds 86% by weight, melting becomes difficult. Preferably, it is 75.5 to 83% by weight.

The _{_{Na 2 0, K 2 0,}} L i 2 0, for ease of melting, the one of at least the mandatory, and 6% by weight or more in total. On the other hand, if it exceeds 20% by weight, the thermal conductivity will not be sufficiently high. Preferably it is 6 to 18% by weight. For the same reason, Na ₂ 0 6-20 wt%, especially 6 to 18 wt%, K 2 0 0 to 10 wt%, it is preferable L i 2 0 is 0 to 10 wt% .

For MgO, CaO, and ZnO, at least one of them is indispensable to increase the chemical durability, and the total amount is 2% by weight or more. On the other hand, if it exceeds 10% by weight, the thermal conductivity will not be sufficiently high. Preferably it is 2 to 8% by weight.

For the same reason, 1 ^ 0 is preferably 1 to 10% by weight, particularly 2 to 10% by weight, Ca 0 is preferably 0 to 10% by weight, and ZnO is preferably 0 to 10% by weight.

Further, Al ₂ 0 ₃ is not essential, since the high Mel enhanced and thermal conductivity of the chemical durability may contain 5 wt% or less. In particular, from the viewpoint of increasing the thermal conductivity, the content is preferably 1% by weight or more.

Further, the glass constituting at least the surface of the glass plate in the present invention has a heat conduction property. The rate is not less than 0.0000240 calZ (cm'sec. * C), preferably not more than 0.000244 ca1 / (cm · sec ·). This glass has a higher heat than ordinary soda-lime glass. Due to the high conductivity, the heat generated by the electric heater is transmitted to the entire surface of the glass, and the time required for the frost to disappear is reduced, as described above. Thermal stress is also reduced.

After the glass having the composition in the above composition range is processed into a predetermined size and shape, an electric heater is provided to form the glass plate with an electric heater of the present invention. For example, silver paste

(A paste printing ink made by mixing fine silver particles and a low-melting glass powder in an organic solvent) and applying an electric heater with a width of about 0.6 mm at regular intervals by the screen method. 'after drying at about C, by baking by heating to about 7 O0 ^e C, the electric heater may be provided on the surface of the glass plate. The glass sheet can be simultaneously subjected to heat strengthening treatment by rapid cooling during this heating.

In the electric heater with glass of the present invention, fragility index value B is preferably 6000m Ha or less, more preferably 5500 m ¹ "below. Fragility index value has a close relationship with the density of the glass, As the density of the glass increases, the brittleness index value B increases and the glass tends to become brittle.In this view, the density of the glass is less than 2.45 gZcc, especially less than 2.43 g / cc. It is preferable to melt the glass having the composition shown in Examples 75 to 101 in Tables 5 and 6, form a plate, and then install an electric heater to prepare a glass plate with an electric heater. 200 g of the raw material powder of the composition was placed in a platinum crucible and then heated and melted with stirring for 4 hours in the atmosphere of 1450 to 1650. The uniformly melted glass of each composition was poured into a glass mold. Was formed into a plate of about 10 cm square with a thickness of 5 ram and cooled.

The obtained glass was annealed at a temperature slightly higher than the temperature at which the viscosity became 10 ″ · ⁵ boise, and after removing the distortion, the glass was cut and polished to obtain a sample having a thickness of 4 mm. the sample in order to remove the surface stress further by polishing, again, temperature was raised at 1 0 O'CZ time to some temperature below the temperature at which the viscosity becomes 10 ^{^14.5} Boyes, held for 3 hours, 60'CZ time To obtain a sample for evaluation.

This sample composition (unit: wt%), the thermal conductivity 31 ^{(Unit: X 10- 5 ca 1 / (} cm * sec · β Ο), the density p (unit: g / cc), fragility index value B (Unit: πΓ ¹ ^{/ 2} ) are shown in Tables 1 and 2. In the table, RCUiMgO + CaO + ZnO, R '2 0 is _{_{Na 2 0 + K 2 O +}} L i 2 0, S i + B denotes the _{_{S i 0 2 + B 2 0}} 3.

Examples 75 to 98 are examples of the glass plate with an electric heating element of the present invention, and Examples 99 to I01 are comparative examples. Example 99-101, less than the thermal conductivity of 0. 00240c a 1 / (cm · s ec · β Ο, lower thermal conductivity than the glass of the present invention.

9 ^

9Z

Z6ZZ0 / 96d £ / lDd 01180 / m 6 OM

9 peaks

92

Z6 £ Z0 / 96df / XDd The glass having the composition of Example 75 in Table 5 and the glass having the composition of Example 99 in Table 6 are melted, and a glass plate formed into a plate shape is cut into a predetermined shape, and an electric heater is provided on the surface of the glass plate. A glass plate with an electric heater was prepared. In other words, a silver paste (paste-like printing ink made by mixing fine silver particles and a low-melting glass powder in an organic solvent) is applied to a glass plate about 35 cm wide and about 100 cm long by the screen method. Twenty-eight strips of 0.6 mm width were applied at intervals of about 3 cm. The applied strip was dried at about 100 ^e C for 5 minutes, and then baked by heating at 700 ^e C for 4 minutes.

Using these glasses, a test for removing fog was performed. That is, the sealing state by attaching these glass plate to the opening of the box of 150X 150X 8 OCM, to control the temperature in the box 24 ^e C, the temperature outside the box to 1 0 ° C. Next, water vapor is sprayed on the inner surface of the glass plate to generate a rip on the entire surface of the glass plate. After about 5 minutes, the current was passed through the heater to heat it from the electric heating element, and the disappearance of fogging on the glass surface was observed.

As a result, the glass obtained in Example 75 was extinguished within 5 minutes, while the glass obtained in Example 99 was still cloudy even after 6 minutes or more. .

Using the glasses obtained in Example 75 and Example 99, a test for removing frost was performed. In other words, these glass plates are attached to the opening of a 150 x 150 x 80 cm box to make it hermetically sealed. Frost is generated on the entire surface of the glass plate. After about 5 minutes, the current was heated from the electric heater through the electric current, and the disappearance of frost on the glass surface was observed.

As a result, the glass obtained in Example 75 had frost removed within 20 minutes, whereas the glass obtained in Example 99 still had frost on the surface even after 25 minutes.

Furthermore, using the glasses obtained in Examples 75, 89 and 99, the glass temperature in the immediate vicinity of the electric heater and the glass temperature at the midpoint between the two electric heaters were measured. Table 7 shows the results. Table 7 Energized heating element Midpoint temperature

Elapsed time Ambient temperature Example 7 5 Example 8 9 Example 9 9

0 min 20 ^eC20 . 20 V at C 20

2 minutes 4 5 2 7. C 2 7 Ό 24 ° C

5 minutes 6 0 Ό 4 2 ° C 4 1 3 8 ^e C

8 minutes 6 5 C4 5. C 44 ° C 40. C

INDUSTRIAL APPLICABILITY According to the present invention, glass having low density and high scratch resistance and suitable for vehicles can be obtained.

According to the tempered glass sheet of the present invention, the scratch resistance of the tempered glass sheet can be extremely enhanced, and breakage of the glass sheet due to the scratch can be suppressed. Also, the weight of the glass plate can be reduced at the same time.

According to the curved glass plate of the present invention, the abrasion resistance of the curved glass plate can be extremely increased, and breakage of the glass plate due to the scratch can be suppressed. Also, the weight of the glass plate can be reduced at the same time.

ADVANTAGE OF THE INVENTION The glass plate with an electric heating element of this invention has the effect that heat conductivity is high and the time required for removal of fogging and frost is short. In addition, since it is difficult to generate thermal stress due to heating of the electric heating element, there is an excellent effect that the possibility of damage due to thermal stress is reduced.

Claims

Scope of word blue

1. A glass suitable for vehicles with essentially the following composition and a density at room temperature of 2.45 gZcc or less.

S i 0 ₂ 74-83 (% by weight),

B _z 0 a 0-5 (% by weight),

Mg 0 0-10 (% by weight),

C a 0 0 ~ 10 (wt%),

Z ηθ 0 ~ 10 (wt%),

_{_{N a 2 0 + K 2 0}} + L i 2 0 6~23 ( wt%),

A 1 ₂ 0 ₃ 0-5

2. A glass according to claim 1, essentially comprising the following composition, and a thermal expansion coefficient of 50 to 300 'C is 80X 10- ⁷ Z ° C or more, the density at room temperature is 2. A tempered glass sheet characterized by being strengthened by heating and rapidly cooling a glass sheet of 45 g / cc or less.

S i 0 ₂ 74-83 (% by weight),

B ₂ 0 ₃ 0 to 5 (% by weight),

S i 0 ₂ + B ₂ 0 ₃ 74-83 (% by weight),

MgO 0-: I 0 (% by weight),

C aO 0-: I 0 (% by weight),

ZnO 0-: I 0 (% by weight),

Na ₂ 0 + ₂₀ + L i ₂₀ 12 to 23 (% by weight),

A 12 0 ₃ 0~ 5 (wt%).

3. Glass contains B ₂ 0 ₃ 0. 5 (wt%) or more, tempered glass of claim 2 wherein.

4. with the glass comprises less than B ₂ 0 ₃ and from 0 to 0.5 (wt%), at room temperature 3. The tempered glass sheet according to claim 2, wherein the density of the tempered glass sheet is 2.43 z / c or less.

5. The glass according to claim 1, wherein the glass sheet having a following composition and having a density at room temperature of 2.45 gZc c or less is bent by heating and softening the glass sheet. Curved glass plate.

S i 0 ₂ 74—80

B ₂ 0 ₃ 0 to 5 (% by weight)

MgO 0-10 (% by weight)

C aO 0 to 10 (% by weight)

ZnO 0-10

_{_{N a 2 0 + K 2 0}} + L 0 10~23 ( wt%)

A 12 0 ₃ 0-5 (% by weight)

6. Glass is viscosity at 1 0 ^es Boyes become temperature of 700 or less, viscosity 1 ^{0, 4} - ⁵ Boyes become temperature 520 * C or less is claim 5 curved glass plate according.

7. Glass B ₂ 0 ₃ and 0.5 (wt%) containing at least claim 5 or 6 curved glass plate according.

8. Glass B ₂ 0 ₃ and from 0 to 0.5 with contains less than (% by weight), density 2. or less 43 GZC c Claim 5 or 6 curved glass plate according.

9. The glass according to claim 1, wherein at least the surface has essentially the following composition, and the thermal conductivity at room temperature is 0.0000240 calZ (cm'sec '° C) or more. A glass plate with an electric heating element, wherein an electric heating element is provided on the surface.

S i 0 ₂ + B ₂ 0 ₃ 75-86 (% by weight),

However, B ₂ 0 ₃ 0 to 5 (% by weight),

MgO + CaO + ZnO 2 to: 10 (% by weight), _{_{N a 2 0 + K 2 0}} + L i 2 0 6~20 ( wt%),

A 12 0 ₃ 0~ 5 (wt%).

0. At least the surface has essentially the following composition and the thermal conductivity at room temperature is

0.20024cal / (cmsec) The glass plate with an electric heating element according to claim 9 or above.

S i 0 ₂ + B ₂ 0 ₃ 7 5.5 to 86 (% by weight),

However, B ₂ 0 ₃ 0 to 5 (% by weight),

MgO + CaO + ZnO 2 ~ 10 (wt%),

_{_{N a 2 0 + K 2 0}} + L i 2 0 6~20 ( wt%),

A 1 ₂ 0 ₃ 1~ 5 (wt%).