JP2017088106A - Window glass for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a window glass for an automobile, capable of suppressing decrease in strength of a glass plate by a shielding film, and applicable to a glass plate with small curvature.SOLUTION: A window glass for an automobile includes a curved rectangular glass plate, and a shielding film laminated on the glass plate. A maximum distance to a length of a straight line connecting centers of a pair of opposite sides of the glass plate, between the straight line and the glass plate is 4% or less, and a difference between a linear expansion coefficient of the shielding film and a linear expansion coefficient of the glass plate at 500°C is within ±5% of the linear expansion coefficient of the glass plate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an automotive window glass.

  In general, a dark-colored shielding film is provided on the periphery of the window glass attached to the automobile, thereby preventing the attachment member to the vehicle body or the terminal of the electrical component from being seen from outside the vehicle ( For example, Patent Document 1). Such a shielding film is formed, for example, by applying a pasted ceramic color composition on a glass plate with glass powder as a base, followed by heating, molding, and cooling steps together with the glass plate.

JP 2000-154038 A

  In the glass plate cooling step as described above, the glass plate is strengthened by rapidly cooling from a heating temperature of 650 to 700 ° C. However, since the above-described shielding film has a linear expansion coefficient different from that of the glass plate, tensile stress from the ceramic color composition is applied to the surface of the glass plate in the cooling step. Therefore, the surface compressive stress value of the glass plate is reduced by the tensile stress from the ceramic color composition, and there is a problem that the strength of the glass plate is lowered in the region where the shielding film is provided.

  In order to solve this, as described in Patent Document 1 (for example, paragraph 0005), generally, a technique for reducing the linear expansion coefficient of a ceramic color composition is known. In this method, it is preferable to make the linear expansion coefficient as close to 0 as possible so that tensile stress does not act on the surface of the glass plate. However, in order to reduce the linear expansion coefficient of the ceramic color composition, the content of glass powder or the like must be changed. Furthermore, when a ceramic color composition having a low linear expansion coefficient is used, the ceramic color composition Since the melting temperature of the ceramic color composition is increased by changing the amount and type of frit and colorant contained in the product, it is necessary to increase the heating temperature of the glass plate by about 10 to 20 ° C.

  By the way, some window glass attached to an automobile has a curve. However, the smaller the curve, the smaller the distortion, so that the heating temperature of the glass plate needs to be lowered by about 10 to 20 ° C. . However, when the heating temperature of the glass plate is lowered in this way, as described above, there has been a problem that the reduction in the strength of the glass plate due to the shielding film cannot be suppressed.

  The present invention has been made to solve the above problems, and provides an automotive window glass that can suppress a decrease in strength of a glass plate due to a shielding film and can be applied to a glass plate having a small curvature. Objective.

This invention provides the window glass of the aspect hung up below, and its manufacturing method.
Item 1. A curved rectangular glass plate;
A shielding film laminated on the glass plate;
With
The maximum distance between the straight line and the glass plate with respect to the length of a straight line connecting the centers of a pair of opposing sides of the glass plate is 4% or less,
The window glass for motor vehicles in which the difference of the linear expansion coefficient of the said shielding film and the linear expansion coefficient of the said glass plate in 500 degreeC is less than +/- 5% of the linear expansion coefficient of the said glass plate.

Item 2. Item 2. The automobile window glass according to Item 1, wherein the glass plate is disposed on a roof of the automobile.

Item 3. Item 3. The window glass for an automobile according to Item 1 or 2, wherein the surface stress of the region where the shielding film is laminated is a compressive stress.

Item 4. Item 4. The window glass for an automobile according to Item 3, wherein the surface compressive stress is 50 MPa or more.

Item 5. Item 5. The window glass for an automobile according to any one of Items 1 to 4, wherein the shielding film is laminated in a region within 30 mm from an edge of the glass plate.

Item 6. Preparing a rectangular glass plate;
Applying a shielding film paste to a portion of the glass plate;
Heating the glass plate together with the shielding film paste;
Molding the glass plate into a predetermined curved shape together with the shielding film paste;
Cooling the glass plate together with the shielding film paste to obtain a window glass having the glass plate and the shielding film;
With
In the forming step, the glass is such that the maximum distance between the straight line and the glass plate is 4% or less with respect to the length of a straight line connecting the centers of a pair of opposing sides of the glass plate. Curving the board,
The manufacturing method of the window glass for motor vehicles whose difference of the linear expansion coefficient of the said shielding film and the linear expansion coefficient of the said glass plate in 500 degreeC is less than +/- 5% of the linear expansion coefficient of the said glass plate.

  According to the present invention, it is possible to suppress a decrease in strength of the glass plate due to the shielding film, and to apply to a glass plate having a small curvature.

It is a top view of one embodiment of the window glass concerning the present invention. It is a figure which shows the measuring method of the amount of doubles concerning the curvature along a X-axis direction. It is a figure which shows the measuring method of the amount of doubles concerning the curvature along a Y-axis direction. It is a schematic plan view which shows the measurement position of the thickness of a glass plate. It is a table | surface which shows the composition of the ceramic color composition which concerns on Examples 1-6 and Comparative Examples 1-6. It is a table | surface which shows the result of the evaluation test of the window glass which concerns on Examples 1-6 and Comparative Examples 1-6.

  Hereinafter, an embodiment of an automotive window glass according to the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a window glass according to the present embodiment. As shown in FIG. 1, the window glass according to the present embodiment is attached to an automobile, and is laminated on the glass plate 1 and the shielding film 2 that is laminated on the glass plate 1 and shields the field of view from the outside of the vehicle. And. Here, the window glass attached to the roof of a motor vehicle is demonstrated as an example. However, the window glass according to the present invention can be disposed on any of the front, rear, and side portions of the vehicle body other than the roof. Hereinafter, each member will be described in detail.

<1. Glass plate>
The glass plate 1 can be a known glass plate, and can be formed of heat ray absorbing glass, general clear glass, green glass, UV green glass, or the like. However, these glass plates 1 need to realize visible light transmittance in accordance with the safety standards of the country where the automobile is used. For example, the solar radiation absorptivity can be secured and the visible light transmittance can be adjusted to satisfy the safety standard. Below, an example of a composition of clear glass, heat ray absorption glass, and soda-lime-type glass is shown.

(Clear glass)
SiO ₂ : 70 to 73% by mass
Al ₂ O ₃ : 0.6 to 2.4% by mass
CaO: 7 to 12% by mass
MgO: 1.0 to 4.5 mass%
R ₂ O: 13 to 15% by mass (R is an alkali metal)
Fe total iron oxide in terms of _{2 O 3 (T-Fe 2} O 3): 0.08~0.14 wt%

(Heat ray absorbing glass)
The composition of the heat-absorbing glass, for example, based on the composition of the clear glass, the proportion of the total iron oxide in terms of _{Fe 2 O 3 (T-Fe} 2 O 3) and 0.4 to 1.3 wt%, CeO ₂ ratio as 0-2 mass%, the proportion of TiO ₂ and 0 to 0.5 wt%, framework component of the glass (mainly, SiO ₂ and Al ₂ O ₃₎ to T-Fe ₂ O _3, CeO _The composition can be reduced by an increase of ₂ and TiO ₂ .

(Soda-lime glass)
SiO ₂ : 65-80% by mass
Al ₂ O ₃ : 0 to 5% by mass
CaO: 5 to 15% by mass
MgO: 2% by mass or more NaO: 10-18% by mass
K ₂ O: 0 to 5% by mass
MgO + CaO: 5 to 15% by mass
Na ₂ O + K ₂ O: 10 to 20% by mass
SO ₃ : 0.05 to 0.3% by mass
B ₂ O ₃ : 0 to 5% by mass
Fe total iron oxide in terms of _{2 O 3 (T-Fe 2} O 3): 0.02~0.03 wt%

The linear expansion coefficient of the glass plate 1 (thermal expansion rate) varies with temperature, it is ^{1 × 10 -6 ~10 × 10 -6} / ℃.

  Although the thickness of the glass plate 1 which concerns on this embodiment is not specifically limited, It is preferable to set it as 1.0-5.0 mm, It is more preferable to set it as 3.0-5.0 mm, 4.0-5. Particularly preferred is 0 mm.

  Moreover, the glass plate 1 which concerns on this embodiment has comprised the curved shape. Although the shape of the curve is not particularly limited, it may be curved along at least one of the X-axis direction and the Y-axis direction in FIG.

  Here, a method for measuring a double amount indicating the degree of curvature of the glass plate 1 will be described. For example, in order to measure the amount of double bending along the X-axis direction of the glass plate 1, a straight line connecting the center of the front side 11 and the center of the rear side 12 of the glass plate 1 as shown in FIG. L1 is set, and as shown in FIG. 2B, the largest distance among the distances between the straight line L1 and the glass plate 1 is defined as a double amount D1. Similarly, in order to measure the amount of double bending along the Y-axis direction of the glass plate 1, a straight line L2 connecting the center of the left side 13 and the center of the right side 14 of the glass plate 1 as shown in FIG. As shown in FIG. 3B, the largest distance among the distances between the straight line L2 and the glass plate 1 is defined as a double amount D2. And in this embodiment, the ratio of the amount D1 of curvature of the curve in the X-axis direction to the length in the X-axis direction of the glass plate 1 (the length of the straight line L1), and the length of the glass plate 1 in the Y-axis direction ( Of the ratio of the double amount D2 of the curve in the Y-axis direction to the length of the straight line L2, the smaller ratio is 4% or less, and can be 3% or less, and further 2% or less. In particular, a window glass for a roof of an automobile often has a small ratio of the amount of double as described above.

  Here, an example of a method for measuring the thickness when the glass plate 1 is curved will be described. First, about a measurement position, as shown in FIG. 4, it is two places of the both ends of the straight line L2 mentioned above in the glass plate 1. As shown in FIG. The measuring instrument is not particularly limited, and for example, a thickness gauge such as SM-112 manufactured by Teclock Co., Ltd. can be used. At the time of measurement, the glass plate 1 is placed on a flat surface so that the curved surface is placed, and the end of the glass plate 1 is clamped by the thickness gauge.

  This glass plate 1 is tempered by heating and cooling processes of a manufacturing method described later, and is formed so as to exhibit a compressive stress value on both surfaces (surfaces) in the thickness direction and a tensile stress value near the center in the thickness direction. The The surface compressive stress value on both surfaces in the thickness direction is preferably 75 MPa or more, and more preferably 100 MPa or more. However, in order to ensure the strength of the glass plate 1, it is preferable that the surface compressive stress value on both surfaces in the thickness direction including the region where the shielding film 2 is formed is 50 MPa or more, as will be described later. Moreover, the strength of the glass plate can also be evaluated by performing a falling ball test. In this case, it is preferable that the glass plate does not break when a 227 g steel ball is dropped from a height of 2 m, and more preferably that the glass plate does not break when the steel ball is dropped from a height of 2.5 m. It is particularly preferable that the glass plate does not break when the steel ball is dropped from a height of 3.0 m.

<2. Shielding film>
Next, the shielding film 2 will be described. A shielding film 2 as shown in FIG. 1 is formed on the glass plate 1 according to the present embodiment. The shielding film 2 is a dark color layer laminated on the inner surface of the glass plate, and is laminated mainly along the periphery of the glass plate. With this shielding film 2, various members such as an adhesive when the glass plate 1 is attached to the vehicle body, or electrical components such as terminals can be prevented from being seen from the outside. However, the position on the glass plate 1 where the shielding film 2 is formed is not particularly limited, and can be formed at other positions. In addition, when providing the shielding film 2 in the periphery of the glass plate 1, forming in the area | region within 30 mm from the edge of the glass plate 1 is preferable.

  The form of the shielding film 2 is not particularly limited. In addition to being uniformly formed on the periphery of the glass plate 1, it is formed by arranging a large number of minute dots, or the shape and size of the dots are changed. It can also be formed in a gradation.

  The shielding film 2 is formed, for example, by applying a paste-like ceramic color composition, which will be described later, to the glass plate 1 and heating and cooling the glass plate 1 together. Hereinafter, the ceramic color composition will be described.

  The ceramic color is usually an inorganic pigment powder, an inorganic filler, and a low-melting glass powder dispersed in a form suitable for coating or printing on the glass plate 1, more specifically in a resin solvent solution (oil). Paste form or paint form. Since this ceramic color is exposed to a high temperature (500 ° C. or higher) during baking, the organic matter decomposes and dissipates after baking and does not remain in the baked coating film.

  In the present specification, the term “ceramic color composition” is used for an inorganic powder mixture excluding the oil. The blending amount is also displayed with reference to inorganic powder alone.

  The ceramic color composition includes glass powder, inorganic pigment powder, and inorganic filler powder. For example, it can be set as the ceramic color composition containing 50 to 90 weight% of glass powder, 10 to 40 weight% of inorganic pigment powder, and 0 to 10 weight% of inorganic filler powder.

As glass powder, it can be set as the following compositions, for example.
SiO ₂ 25-50% by weight
B ₂ O ₃ 1-9% by weight
Bi ₂ O ₃ 1-60% by weight
ZnO 20-40% by weight
TiO ₂ 1-10% by weight
Li ₂ O 1-10% by weight
Na ₂ O 1-10% by weight
K ₂ O 0~10 weight%
ZrO ₂ 0-5% by weight
V ₂ O ₅ 0 to 5 wt%
F 0-5% by weight

  The glass powder is prepared in the following manner, for example, according to a conventional method. That is, at the time of melting, the batch raw material is mixed in an amount that should be the above-mentioned formulation to obtain a batch composition. The batch mixture is melted at 1100-1300 ° C. and quenched in water. The obtained popcorn shape or glass flaked with a roll is wet-ground using an alumina ball or the like in a ball mill. The particle size of the glass is optimally in the range of 0.1 to 20 μm, preferably 0.5 to 10 μm. Coarse particles exceeding 20 μm may cause clogging in screen printing, so it is preferable to remove them by classification or scraping with a screen.

As the inorganic pigment powder, those similar to those conventionally used can be used. This includes for example CuO · Cr ₂ O _{3 (black), CoO · Cr 2 O 3} ( black), Fe ₂ O ₃ (Brown), TiO _{2 (white), CoO · Al 2 O 3} ( blue), NiO · Cr ₂ O ₃ (green) and the like are included. The inorganic pigment powder is suitably blended in the composition in an amount of 10 to 40%.

  The inorganic filler powder is selected from those that do not melt at high temperatures. For example, when a silver paste is overprinted as a heat ray on a ceramic color, the silver migrates during the heating and colors the base glass in an amber color. To prevent this, for example, Al, Zn, Fe, A metal powder such as Ni, Sn, or Cu is preferably added as an inorganic filler. Also, metals such as alumina, silica, zircon, zirconate silicate, and zinc white are used to control fluidity when the ceramic collar is heated at a high temperature and prevent adhesion to the mold (improving releasability). Oxides can also be added as the inorganic filler. Furthermore, in order to adjust the linear expansion coefficient of the ceramic color, it is also possible to add a low expansion powder such as β-eucryptite, β-spodumene, cordierite, fused silica or the like as the inorganic filler.

  The particle size of each of the inorganic filler powders described above is generally better because the original function and effect often depends on the surface area of the particles. However, if it is too fine, there is a disadvantage in that the fusion temperature of the ceramic color is rapidly increased. Is preferably selected from the range of about 0.05 to 5.0 μm, preferably about 0.1 to 1.0 μm.

  If the added amount of the inorganic filler powder exceeds 10%, the fusing temperature of the ceramic color rises, resulting in problems such as poor adhesion to the base glass and primer penetration in the bonding process. However, the addition of the inorganic filler powder does not need to be particularly essential if the purpose can be overcome by other methods or can be solved by the characteristics of the low melting point glass itself. For example, silver migration can be solved by increasing the film thickness of the ceramic collar, and even if it is releasable, if it uses a material that crystallizes into low-melting glass, it has sufficient releasability in the out-of-furnace crimping process. In such a case, the addition of the inorganic filler powder is not particularly necessary.

  The ceramic color composition is a resin having a good thermal decomposability in which the glass powder, the inorganic pigment powder, and the inorganic filler powder are converted into a relatively high boiling point solvent such as pine oil, α-terpineol, and butyl carbitol acetate. It can be prepared by mixing and dispersing in an oil in which cellulose resin, acrylic resin, methacrylic resin and the like are dissolved. Moreover, this ceramic color composition can also be prepared according to the coating method on the glass plate 1, for example, an ink form, a paint form, etc. suitable for those methods.

  The paste is preliminarily dried by heating, but instead of this oil, an ultraviolet curable acrylate or methacrylate oligomer containing a photopolymerization initiator may be used as an oil component to make an ultraviolet drying type. The viscosity of the paste is optimally 100-600 poise (25 ° C.) for screen printing.

  The blending ratio of the inorganic mixed powder and the resin solvent solution (vehicle) in the various forms of the composition thus obtained is appropriately determined according to the coating method to which the resulting composition is applied, and is not particularly limited. However, in the case of an ink form suitable for screen printing or the like, it is preferable to select from the range of 60 to 90% by weight of the inorganic mixed powder and 10 to 40% by weight of the vehicle. It is suitable to be selected from a mixing ratio of 30 to 70% by weight of the mixed powder and 30 to 70% by weight of the vehicle. The ink form and the paint form can be prepared according to a general method, for example, by dispersing the inorganic mixed powder in a resin solvent solution using a roll mill, a sand mill, a ball mill or the like.

  The ceramic color composition can be formed by a screen printing method, but it can also be produced by transferring a baking transfer film to a glass plate and baking it. As conditions for screen printing, for example, polyester screen: 355 mesh, coat thickness: 20 μm, tension: 20 Nm, squeegee hardness: 80 degrees, mounting angle: 75 °, printing speed: 300 mm / s, The shielding film 2 can be formed by drying at 150 ° C. for 10 minutes.

  The ceramic color composition according to the present invention is not limited to the above, but at least the linear expansion coefficient of the shielding film 2 formed by the ceramic color composition according to the present invention approximates the linear expansion coefficient of the glass plate 1. In particular, the difference between the linear expansion coefficient of the shielding film 2 and the linear expansion coefficient of the glass plate 1 at 500 ° C. is set to be within ± 5% of the linear expansion coefficient of the glass plate 1 (hereinafter referred to as “below”). , This ratio is sometimes called the difference rate). The linear expansion coefficient has an influence from all the compositions and cannot be generally stated. For example, by adjusting the amounts of Bi and Zn, a glass having a difference rate of 4% or less can be obtained. .

<3. Window glass manufacturing method>
Next, an example of the manufacturing method of the window glass which concerns on this embodiment is demonstrated. A heating furnace, a molding device, and a cooling device are arranged in this order from upstream to downstream in the production line for producing the window glass according to the present embodiment. A roller conveyor is arranged from the heating furnace to the molding device and the cooling device downstream thereof, and the glass plate 1 to be processed is conveyed by the roller conveyor. The glass plate 1 is formed in a flat plate shape before being carried into the heating furnace, and after the shielding film 2 described above is laminated on the glass plate 1, the glass plate 1 is carried into the heating furnace. Although the heating temperature in a heating furnace is based also on a composition of a glass plate, it can be set as 640-670 degreeC, for example.

  The glass plate 1 that has passed through the heating furnace is formed in a forming apparatus. For example, when the glass plate 1 is carried onto the roller conveyor of the molding apparatus, the roller conveyor is lowered and the glass plate 100 is supported by the lower mold. That is, the glass plate 1 is transferred from the roller conveyor to the lower mold. Subsequently, the upper die is lowered, and the glass plate 1 is pressed by the upper die and the lower die. Thereby, the glass plate 1 is shape | molded in the curved shape.

  When the formation of the glass plate is completed in this way, the roller conveyor is raised and the glass plate 1 is supported. Thereafter, the glass plate 1 is unloaded from the molding device by a roller conveyor and conveyed to the cooling device. In the cooling device, the blower is driven, and air is blown from above and below the glass plate 1 to be cooled together with the shielding film 2. Thus, the manufacture of the window glass is completed. Note that this manufacturing method is merely an example, and various other methods can be employed. For example, as described in JP-A-8-231236, cooling can be performed by blowing air in the mold, or cooling can be performed a plurality of times.

<4. Features>
The window glass according to the present embodiment has the following characteristics.
(1) The linear expansion coefficient close to that of the glass plate 1 is such that the difference between the linear expansion coefficient of the shielding film 2 and the linear expansion coefficient of the glass plate 1 at 500 ° C. is ± 5% of the linear expansion coefficient of the glass plate 1. Since the shielding film 2 is used, the tensile stress acting on the glass plate 1 from the shielding film 2 can be suppressed without increasing the heating temperature. As a result, in the glass plate 1, it is possible to prevent a decrease in surface compressive stress at the location where the shielding film 2 is laminated.

(2) The heating temperature needs to be lower than usual in order to reduce the double amount of the glass plate 1 and to reduce the strain. However, in the conventional shielding film, the strength decreases when the heating temperature is lowered. There was a problem to do. On the other hand, in this embodiment, since the shielding film having the linear expansion coefficient as described above is used, even when the heating temperature is low, the glass plate 1 can be curved with a small amount of double, And it can prevent that a distortion | strain is formed in a glass plate.

(3) As described above, according to the window glass according to the present embodiment, by using the shielding film having the linear expansion coefficient as described above, distortion due to a small amount of double can be suppressed, and strength can be increased. It is possible to satisfy both of the conventional conflicting matters that the reduction can be suppressed.

  Examples of the present invention will be described below. However, the present invention is not limited to the following examples.

<1. Ceramic color composition for shielding film>
An amount of batch raw material mixture having a glass composition as shown in the table of FIG. 5 was melted at 1200 to 1250 ° C. The molten glass was quenched in water to obtain popcorn glass. This glass was pulverized in a ball mill using water-wet and alumina balls, and the resulting slurry was dried and sieved to prepare a powder glass.

As the inorganic pigment, a black pigment (CuO · CrO ₃ , # 3700 manufactured by Asahi Kasei Kogyo Co., Ltd.) was used.

  Each inorganic filler shown in FIG. 5 was adjusted to a particle size of 0.1 to 1.0 μm and used.

  Next, with respect to 100 parts by weight of the ceramic color composition powder shown in FIG. 5, 93% by weight of pine oil, 4% by weight of ethyl cellulose (manufactured by Dow Chemical Co., STD-20) and isobutyl methacrylate resin (trade name; Elbasite) (# 2045, manufactured by DuPont) 30 parts by weight of oil consisting of 3% by weight was added and dispersed with three rolls to obtain a ceramic color paste. The viscosity was in the range of 270-320 poise (25 ° C.).

  Moreover, the linear expansion coefficient and difference rate in 500 degreeC are as showing in FIG.

<2. Glass plate>
Float glass (model number FL4) manufactured by Nippon Sheet Glass Co., Ltd. was used. The shape was 800 × 500 mm and the thickness was 4 mm. The linear expansion coefficient at 500 ° C. was 9.29 × 10 ⁻⁶ / ° C.

<3. Window glass manufacturing method>
The ceramic color compositions according to Examples 1 to 6 and Comparative Examples 1 to 6 were applied by screen printing to a peripheral edge 30 mm from the edge of the glass plate with a thickness of 13 μm. Subsequently, after heating at a temperature (unit: ° C.) shown in FIG. 6, molding was performed such that the amount of doubled bending in the Y-axis direction with respect to the length in the Y-axis direction was 2%. Then, it cooled with the cooling device and completed the window glass which concerns on Examples 1-6 and Comparative Examples 1-6.

<4. Evaluation method>
The following three types of tests were performed on the window glass manufactured as described above.

<4-1. Distortion>
A black base is placed in front of a vertically standing lattice plate (a black line with a width of 5 mm and a pitch of 50 mm on a white background), and the window glass according to Examples 1 to 6 and Comparative Examples 1 to 6 is horizontally placed thereon. Arranged. And the image which a grating | lattice reflects on the surface of a window glass was observed. By changing the width of the reflected line and the change in the pitch of the line, the surface distortion was subjected to sensory evaluation in the following four stages.
・ Local change is not seen Class 1 ・ Local change is seen, but it can be generally used for automobiles Class 2 ・ Overall changes can be seen, but it can be used for cars in general Class 3 ・Cannot be used locally or generally for automobiles

<4-2. Falling ball test>
In order to prevent the glass from scattering, a tape was applied to the area where the shielding film was formed on the window glass. Next, 227 g of steel balls were dropped onto the taped area. The height of the steel ball was raised from 1 m to 0.2 m, and the height at which the window glass broke was recorded.

<4-3. Stress value>
Using a glass surface stress meter GSM-01 manufactured by Orihara Seisakusho Co., Ltd., the surface compressive stress in the region where the shielding film was formed was measured according to JIR R3222 double strength glass (surface compressive stress measuring method).

<4-4. Result>
The results of the three types of tests are as shown in FIG. As shown in FIG. 5, at 500 ° C., the difference in linear expansion coefficient between the shielding films of Examples 1 to 6 and the glass plate was within 5% of the linear expansion coefficient of the glass plate. On the other hand, in Comparative Examples 1-6, all were larger than 20%. Further, as shown in FIG. 6, the molding temperatures of Examples 1 to 6 are 10 to 30 ° C. lower than those of Comparative Examples 1 to 6 in order to mold a glass plate having a small amount of double. Thereby, even if it was a glass plate with a small amount of doubles, in Examples 1-6, distortion became small. Moreover, since the shielding film having a linear expansion coefficient close to the linear expansion coefficient of the glass plate as described above was used, even if the molding temperature was not high, the surface compressive stress was 50 MPa or more. The falling ball test showed high strength.

  On the other hand, Comparative Examples 1 to 6 increased the molding temperature due to the composition of the shielding film, but this molding temperature was incompatible with a glass plate having a small amount of double. That is, all the distortions were grade 3 or grade 4, and overall distortion was seen, or it became unusable for automobiles. In the falling ball test, cracks were observed even when the steel ball dropped from a low position. That is, it was found that the strength was low. Furthermore, the surface compressive stress which shows that was 30 MPa or less, and it was found that the surface compressive stress was considerably low as compared with Examples 1-6. From the above, it was found that the window glasses according to Examples 1 to 6 can suppress the decrease in stress of the glass plate due to the shielding film, reduce the amount of double, and further reduce the distortion.

1 Glass plate 2 Shielding film

Claims (5)

A curved rectangular glass plate;
A shielding film laminated on the glass plate;
With
The maximum distance between the straight line and the glass plate with respect to the length of a straight line connecting the centers of a pair of opposing sides of the glass plate is 4% or less,
The window glass for motor vehicles in which the difference of the linear expansion coefficient of the said shielding film and the linear expansion coefficient of the said glass plate in 500 degreeC is less than +/- 5% of the linear expansion coefficient of the said glass plate.   The window glass for an automobile according to claim 1, wherein the glass plate is disposed on a roof of the automobile.   The window glass for automobiles according to claim 1 or 2, wherein the surface stress of the region where the shielding film is laminated in the glass plate is a compressive stress.   The automotive window glass according to claim 3, wherein the surface compressive stress is 50 MPa or more.   The window glass for automobiles according to any one of claims 1 to 4, wherein the shielding film is laminated in a region within 30 mm from an edge of the glass plate.