JPH09124340A - Glass plate having electric heating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a glass having an electric heating element capable of removing the clouding in a short time required therefor. SOLUTION: This glass plate having an electric heating element is obtained by providing the electric heating element on the surface of the glass plate having at least the surface of a composition consisting essentially of 75-86wt.% total amount of SiO2 and B2 O3 , 0-5wt.% B2 O3 , 2-10wt.% total amount of MgO, CaO and ZnO, 6-20wt.% total amount of Na2 O, K2 O and Li2 O and 0-5wt.% Al2 O3 and further >=0.002490cal/(cm∼sec∼ deg.C) thermal conductivity at ambient temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass with an electric heating element, which is suitable for a rear glass of a vehicle.

[0002]

2. Description of the Related Art Conventionally, as a rear glass of a passenger car or the like, a glass provided with an electric heating element for removing fogging has been widely used. However, in general, these glasses have a problem that it takes a few minutes to a few dozen minutes to remove the once clouded fogging of the entire glass surface and restore the backward visibility, and in cold regions. , 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 shorten the time required for removing fog and frost as much as possible.

[0003]

In order to improve the ability to remove fogging and frost, a method of increasing the amount of heat generated by the electric heating element can be considered, but in that case, power consumption increases,
The problem of burdening the battery, the temperature near the heating element becomes high, and the temperature difference between the heating element and other parts becomes large, which may cause large thermal stress inside the glass and lead to damage. There was a problem that there is.

Further, a method of narrowing the arrangement interval of the electric heating elements can be considered, but in this case, the total length of the electric heating elements becomes long, the power consumption increases, and the rear visual field itself is obstructed by the electric heating elements. There is.

An object of the present invention is to eliminate the above-mentioned drawbacks in the conventional glass with an electric heating element.

[0006]

DISCLOSURE OF THE INVENTION According to the present invention, at least the surface of a glass plate having essentially the following composition and a thermal conductivity at room temperature of 0.00246 cal / (cm · sec · ° C.) or more: Provided is a glass plate with an electric heating element, characterized in that an electric heating element is provided on the glass plate.

SiO ₂ + B ₂ O ₃ 75 to 86 (wt%), provided that B ₂ O _{30 to} 5 (wt%), MgO + CaO + ZnO 2 to 10 (wt%), Na ₂ O + K ₂ O + Li ₂ O 6 to 20 ( % By weight), Al ₂ O ₃ 0-5 (% by weight).

The phrase "at least on the surface" means that the glass composition of the laminated glass or the outermost layer of the double glazing satisfies the above conditions.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The composition of the glass constituting the glass plate with an electric heating element of the present invention will be described. SiO ₂ and B ₂ O ₃ are components that are glass network formers. If the total amount of these is less than 75% by weight, the thermal conductivity will not be sufficiently high. If it exceeds 86% by weight, melting becomes difficult. It is preferably 75.5 to 83% by weight.

In particular, B ₂ O ₃ is not essential, but the meltability can be improved by containing it. On the other hand, in the present invention, the content of B ₂ O ₃ is up to 5% by weight. If it exceeds 5% by weight, the life of the kiln may be shortened due to the scattering of boric acid during melting. Furthermore, since mechanical properties such as thermal expansion are different from so-called soda lime glass, it becomes difficult to simply apply the same device to the soda lime glass for manufacturing and processing.

For Na ₂ O, K ₂ O and Li ₂ O,
In order to facilitate melting, at least one of them is essential, and the total amount is 6% by weight or more. On the other hand, if it exceeds 20% by weight, the thermal conductivity will not be sufficiently high. It is preferably 6 to 18% by weight. For the same reason, Na ₂
It is preferable that O is 6 to 20% by weight, particularly 6 to 18% by weight, K ₂ O is 0 to 10% by weight, and Li ₂ O is 0 to 10% by weight.

With respect to MgO, CaO and ZnO, at least one of them is indispensable in order to enhance the chemical durability, and the total amount is 2% by weight or more. On the other hand, 10% by weight
If it exceeds, the thermal conductivity will not be sufficiently high. It is preferably 2 to 8% by weight. For the same reason, MgO is 1
-10 wt%, especially 2-10 wt%, CaO is 0-1
It is preferable that 0 wt% and ZnO be 0 to 10 wt%.

Further, although Al ₂ O ₃ is not essential, it is added in an amount of 5% by weight to improve chemical durability and thermal conductivity.
The following can be contained. In particular, from the viewpoint of increasing the thermal conductivity, it is preferably contained in an amount of 1% by weight or more.

In the present invention, "essentially" means that the effect of the present invention is achieved, that is, high thermal conductivity is compatible with easy strengthening and scratch resistance, which are essential physical properties for vehicle glass. As long as it means, it means that other components can be added. Other components include additives for homogenizing glass, coloring agents for controlling transmittance of ultraviolet light, visible light, infrared light, and fining agents, and Fe ₂ O
₃ , CoO, NiO, CeO ₂ , TiO ₂ , V ₂ O ₅ ,
Cr ₂ O ₃ , SnO ₂ , Se, SO ₃ , NO ₃ , As ₂
O ₃ , Sb ₂ O ₃ , F, Cl and the like are exemplified.

The glass constituting at least the surface of the glass plate of the present invention has a thermal conductivity of 0.00240.
cal / (cm · sec · ° C) or more, preferably 0.0
It is not less than 0244cal / (cm · sec · ° C). Since this glass has a higher thermal conductivity than ordinary soda lime type glass, heat generated from the electric heating element is quickly transmitted to the entire surface of the glass, and the time required for disappearance of fog and frost is shortened. Further, as described above, the thermal stress due to the temperature distribution generated in the glass surface is also reduced.

The glass having a composition within the above composition range is processed into a predetermined size and shape and then provided with an electric heating element to form the glass plate with an electric heating element of the present invention. For example, a silver paste (paste printing ink formed by mixing fine silver particles and a low melting point glass powder organic solvent) is used, and an electric heating element having a width of about 0.6 mm is applied at regular intervals by a screen method. After drying at about 100 ° C. and heating at about 700 ° C. and baking, the electric heating element can be provided on the surface of the glass plate. The glass plate can be heat-strengthened at the same time by quenching during this heating.

In the composition range of the present invention, the use of glass having a density of 2.47 g / cc or less also has the effect of enhancing the scratch resistance of the glass plate.

In this case, as the index of scratch resistance of glass, the brittleness index value B proposed by Lawn et al. Is used (BR Lawn and DB Marshall, J. Am. Ceram. Soc., 62 [7-
8] 347-350 (1979)). Here, the brittleness index value B is defined by the equation (1) from the Vickers hardness H _v of the material and the fracture toughness value K _c .

[0019]

(Equation 1)

A major problem in applying this brittleness index to glass is that the fracture toughness value K _c is difficult to evaluate accurately. Therefore, the present inventor studied several methods, and quantified brittleness from the relationship between the size of the indenter traces remaining on the glass surface when the Vickers indenter was pushed in and the lengths of cracks generated from the four corners of the traces. I found that I can evaluate it. The relationship is defined by equation (2).

[0021]

(Equation 2)

Here, P is the pushing load (unit: N) of the Vickers indenter, and a and c are the diagonal length of the Vickers indentation and the length of the cracks generated from the four corners (symmetrical including the indenter trace). The total length of the two cracks).

The brittleness index value B (unit: m ^-1/2 ) of the glass can be easily evaluated by using the dimensions of the Vickers indentation formed on the surface of each type of glass and the equation (2).

In the glass with an electric heating element of the present invention, the brittleness index value B is preferably 6000 m ^-1/2 or less, more preferably 5500 m ^-1/2 or less. The brittleness index value has a close relationship with the density of the glass, and as the glass density increases, the brittleness index value B increases, and the glass tends to become brittle. From this viewpoint, the density of the glass is preferably 2.47 g / cc or less, and particularly preferably 2.45 g / cc or less.

When the glass contains B ₂ O ₃ , a low brittleness index value is maintained up to a higher density. Therefore, for those containing 0.5% by weight or more of B ₂ O ₃ , the density of the glass is preferably 2.47 g / cc or less, particularly 2.45 g / cc or less. Also, B
For the ₂ O ₃ which contains less than 0 to 0.5 (wt%), the density of the glass 2.45 g / cc or less, especially 2.
It is preferably 43 g / cc or less.

[0026]

EXAMPLE Glasses having compositions shown in Examples 1 to 27 in Table 1 were melted and formed into a plate shape, and then an electric heating element was installed to prepare a glass with an electric heating element. That is, the raw material powder 2 of each composition
After charging 00g into a platinum crucible, 1450 to 1650
The mixture was heated and melted while stirring in the air at 4 ° C for 4 hours. The uniformly melted glass of each composition was poured into a carbon mold to form a plate of about 10 cm square and a thickness of 5 mm, which was cooled.

The obtained glass was annealed at a temperature slightly higher than the temperature at which the viscosity was 10 ^14.5 poise to remove strain, and then cut and polished to obtain a sample having a thickness of 4 mm. In order to further remove the surface stress due to polishing, the sample polished to give a mirror surface was heated again at a temperature of 100 ° C./hour to a temperature slightly higher than the temperature at which the viscosity was 10 ^14.5 poise, and then held for 3 hours, The sample was gradually cooled at a temperature of ° C / hour and used as an evaluation sample.

The composition (unit: wt%) and thermal conductivity λ (unit: × 10 ^-5 cal / (cm · sec ·) of this sample
)), Density ρ (unit: g / cc), and brittleness index value B (unit: m ^{-1 / 2} ) are shown in Tables 1 and 2. In the table, RO is MgO + CaO + ZnO, R ′ ₂ O is Na ₂ O + K ₂ O +
Li ₂ O and Si + B represent SiO ₂ + B ₂ O ₃ .

Examples 1 to 24 are examples of the present invention.
5 to 27 are comparative examples. In Examples 25 to 27, the thermal conductivity was less than 0.00240 cal / (cm · sec · ° C), and the thermal conductivity was lower than that of the glass of the present invention.

[0030]

[Table 1]

[0031]

[Table 2]

Glass of the composition of Example 1 in Table 1 and Table 2
The glass having the composition of Example 25 therein was melted, a glass plate formed into a plate shape was cut into a predetermined shape, and an electric heating body was provided on the surface of the glass plate to prepare a glass with an electric heating body. That is, a glass paste having a width of about 35 cm and a length of about 100 cm was used with a silver paste (paste printing ink prepared by mixing fine silver particles and a low melting point glass powder with an organic solvent) and a width of 0 by a screen method. 28 with a 6 mm strip at about 3 cm intervals
The book was applied. The coated strip was dried at about 100 ° C. for 5 minutes and then heated at 700 ° C. for 4 minutes to be baked.

Using these glasses, a test for removing haze was conducted. That is, these glass plates are made 150 × 1
It is attached to the opening of a 50 × 80 cm box to be in a sealed state, and the temperature inside the box is controlled at 24 ° C. and the temperature outside the box is controlled at 10 ° C. Next, steam is blown onto the glass plate surface to cause fogging on the entire surface of the glass plate. After a lapse of about 5 minutes, heating was performed by an electric heating body through an electric current, and the disappearance of cloudiness on the glass surface was observed.

As a result, the glass obtained in Example 1 had its haze removed within 5 minutes, while the glass obtained in Example 25 still had a haze on the surface after 6 minutes or more. Was given.

Further, using the glass obtained in Examples 1 and 25, a frost removing property test was conducted. That is, these glass plates were attached to the opening of a box of 150 × 150 × 80 cm to be in a hermetically sealed state. First, the inside and outside of the box were set to −5 ° C., and steam was sprayed on the glass plate surface to frost the entire surface of the glass plate. Generate. After a lapse of about 5 minutes, heating was performed by an electric heating body through an electric current, and the disappearance of frost on the glass surface was observed.

As a result, the glass obtained in Example 1 had frost removed within 20 minutes, whereas the glass obtained in Example 25 still had frost on the surface after 25 minutes or more. Was given.

Further, using the glasses obtained in Examples 1, 15 and 25, the glass temperature in the immediate vicinity of the electric heating element and 2
The glass temperature at the midpoint of the electric heating element of the book was measured. Table 3 shows the results.

[0038]

[Table 3]

[0039]

EFFECT OF THE INVENTION The glass with an electric heating element of the present invention has an effect that the thermal conductivity is high and the time required for removing fog and frost is short. In addition, since the thermal stress due to the heating of the electric heating body is unlikely to occur, there is an excellent effect that the possibility of breakage due to the thermal stress is reduced. Further, the glass of the present invention has an effect that it is less likely to be scratched as compared with ordinary soda lime glass by setting the density to 2.47 / cc or less.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C03C 27/12 C03C 27/12 R (72) Inventor Akira Takada 1150 Hazawa-machi, Kanagawa-ku, Yokohama-shi, Kanagawa Address Asahi Glass Co., Ltd. Central Research Laboratory (72) Inventor Koichi Nagata 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Asahi Glass Co., Ltd.

Claims (3)

[Claims] 1. At least the surface has essentially the following composition and a thermal conductivity at room temperature of 0.00240 cal /
A glass plate with an electric heating element, characterized in that an electric heating element is provided on the surface of the glass plate having a temperature of (cm · sec · ° C) or higher. SiO ₂ + B ₂ O ₃ 75 to 86 (wt%), but B ₂ O _{30 to} 5 (wt%), MgO + CaO + ZnO 2 to 10 (wt%), Na ₂ O + K ₂ O + Li ₂ O 6 to 20 (wt%) , Al ₂ O ₃ 0-5 (% by weight). 2. At least the surface has essentially the following composition and a thermal conductivity at room temperature of 0.00244 cal /
The glass plate with an electric heating element according to claim 1, which has a temperature of (cm · sec · ° C) or more. SiO ₂ + B ₂ O ₃ 75.5 to 86 (wt%), B ₂ O ₃ 0 to 5 (wt%), MgO + CaO + ZnO 2 to 10 (wt%), Na ₂ O + K ₂ O + Li ₂ O 6 to 20 (wt) %), Al ₂ O ₃ 1 to 5 (% by weight). 3. The glass plate has a surface density of at least 2.
The glass plate with an electric heating element according to claim 1 or 2, which has a weight of 47 g / cc or less.