EP3068738A1

EP3068738A1 - Privacy glass for vehicles

Info

Publication number: EP3068738A1
Application number: EP14737342.7A
Authority: EP
Inventors: Fehiman Akmaz
Original assignee: Tuerkiye Sise Ve Cam Fabrikalari AS
Current assignee: TUERKIYE SISE VE CAM FABRIKALARI AS
Priority date: 2013-11-16
Filing date: 2014-03-12
Publication date: 2016-09-21
Also published as: RU2016123396A; RU2016123396A3; WO2015072939A1

Abstract

The present invention is a dark-colored special glass having thickness in the range of 2 mm - 6 mm and having low transmittance, preferably for use in vehicles, and comprising the main composition whose component proportions are given below and comprising selenium in the range of 11-25 ppm in the glass, which is the final product, in order to provide color in smoke tones to the glass by being used together with cobalt oxide: Component Weight % SiO₂ 60-75 Na₂O 10-25 CaO 5-20 MgO 3.5 - 5 Al₂O₃ 0-5 K₂O 0-5 and comprising the following colorants in weight: Component Amount % Fe₂O₃ (In weight) (in the glass) 1.35-1.45 CoO (ppm)(in the glass) 245-255 NaNO₃ (in the mixture) (kg/100kg glass) 0.3 - 0.5 characterized by comprising tin oxide in the range of 0.05-1.0 % in weight reducing Fe⁺³, obtained from ironoxide, to Fe⁺² and increasing permanence of selenium, when compared to glass without tin, in the dark colored glass which is the final product.

Description

SPECIFICATION

PRIVACY GLASS FOR VEHICLES TECHNICAL FIELD

The present invention relates to privacy glasses with low visible and solar transmission preferably in order to be used in sunroofs of vehicles. PRIOR ART

The roofs of vehicles with sunroof are made of glass, and these glasses are called "privacy glass" in the literature. These glasses, provided in said ceiling section, shall be light-proof and heat-proof for driver and passenger health particularly during long-term voyages. Therefore, in obtaining such glasses, color additives are used having absorption both in the visible region and in the infrared region. In order to colorize the glass, pluralities of oxides are added to the batch. One of the most frequently used oxides in coloring is the iron oxide. The iron oxide can be in the form of Fe⁺² and Fe⁺³ in the glass. Fe⁺² provides blue-green color to the glass, and Fe⁺³ provides yellow-green color to the glass.

Coloring by means of iron oxide is mostly used in production of green glasses used in automotive sector. In order to obtain Fe⁺² form in glass, green glasses shall be melted in reducing conditions. In general, the reducing agents comprising carbon enter into reaction with oxygen provided in the melted glass, and thereby they decrease partial pressure of oxygen. Therefore, carbon is frequently used as the reducing agents. However, the performance of carbon on glass changes depending on the size of the particle. This creates a problem in the provision of standardization in production. When excessive carbon is used in glasses with high level of iron, carbon provides sulphate to react at low temperatures, and leads to beforetime consumption of sulphate, and leads to silica problem.

In the invention with the publication number EP0722427, said glass comprises Si0₂ in proportion of 69-75 %, Al₂0₃ in proportion of 0-3 %; B₂0₃ in proportion of 0-5 %, CaO in proportion of 2-10 %, MgO in proportion of 0-2 %, Na₂0 in proportion of 9-17 %, K₂0 in proportion of 0-8 %, Fe₂0₃ in proportion of 0.2-4 % and Se, CoO, Cr₂0₃, NiO, CuO in proportion of 0-0.45 %. In said batch, in case the iron proportion is 1.5 % and lower, the amount of the coloring agents except iron is minimum 0.0002 %. Said composition may comprise florin, zinc, zircon, cerium and titanium oxides; and may comprise barium oxide less ^T-than 4 % and the total percent of soil alkali acids is maximum 10 %. The amount of Se used in said invention is maximum 0.008 %. However, since the amount of Se in the glass is low, this has a negative effect on the stability of the glass color desired to be obtained. In the invention with the publication number EP1218302, there is a green colored, infrared and ultraviolet absorbing glass article having a visible transmittance of up to 60 %. The composition of the glass article uses a standard soda-lime-silica glass base composition and additionally iron oxide in proportion of 0.13-0.9 % in weight, cobalt oxide in proportion of 0.004-0.05 % in weight, selenium in proportion of 0.0005-0.007 % in weight, and chromium oxide in proportion of 0.0015-0.08 % in weight, and preferably titanium oxide in proportion of 0-1 % in weight, as infrared and ultraviolet radiation absorbing materials and colorants. The visible transmittance of said glass in the thickness range 1 mm-10 mm and in the wavelength range 480-565 is maximum 60 % and total solar energy transmittance 50 % and lower. The highest transmittance values given in the invention with publication number EP1218302 are desired to be lower in privacy glasses.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to dark-colored glasses used in vehicle sunroofs, for eliminating the above mentioned disadvantages and for bringing new advantages to the related technical field.

An object of the present invention is to provide a glass whose visible transmittance, UV and solar transmittance are low, in order to decrease the air-conditioner load of the vehicle and in order to prevent deformation of the textile and plastic material in the inner space particularly for use in sun-roofs of vehicles.

Another object of the present invention is to provide a glass which is grey colored. In order to realize all of the above mentioned objects and the objects which are to be deducted from the detailed description below, the present invention is a dark-colored privacy glass having thickness in the range of 2 mm - 6 mm and having low transmission, preferably for use in vehicles, and comprising the main composition whose component proportions are given below and comprising selenium in the range of 11-25 ppm in the glass, which is the final product, in order to provide color in grey tones to the glass by being used together with cobalt oxide: Component Weight, %

Si0₂ 60-75

Na₂0 10-25

CaO 5-20

MgO 3.5 - 5

Al₂0₃ 0-5

K₂0 0-5 and comprising the following colorants in weight:

Accordingly, the present invention comprises tin oxide in the range of 0.05-1.0 % in weight reducing Fe⁺³, obtained from iron oxide, to Fe⁺² and increasing selenium retention, when compared to glass without tin, in the dark colored glass which is the final product. Thus, the glass color can be obtained in pinkish grey tones. In a preferred embodiment of the subject matter invention, there is tin oxide in range of 0.5-1 % in weight.

In another preferred embodiment of the subject matter invention, "L" value of said dark colored glass is minimum in the range of (48.1) - (52.2); value "a" is between (-7.90) - (- 5.98) and value "b" is between (-4.47) - (+3.97).

In another preferred embodiment of the subject matter invention, the visible transmission value (Tv) of said dark colored special glass is minimum 7.5 % and maximum 43 %. In another preferred embodiment of the subject matter invention, the solar transmittance value (Te) of said dark colored special glass is minimum 5 % and maximum 34 %. -In another preferred embodiment of the subject matter invention, the transmission value (Tuv) of said dark colored special glass measured in the ultraviolet region is lower than 11 %.

In another preferred embodiment of the subject matter invention, the transmission value (Tuv) of said dark colored special glass measured in the ultraviolet region is lower than 8 %.

In another preferred embodiment of the subject matter invention, there is 250 ppm CoO in weight. Thus, the color of glass is darkened and the transmittance thereof is decreased. In another preferred embodiment of the subject matter invention, there is 0.3 (kg/100 kg glass) NaN0₃ in weight. Thus, the glass color is more stable.

FIGURES In Figure 1 , the % transmision graphics for 4 mm glass thickness in the presence of 11 ppm and 25 ppm selenium for the crucible melting experiments of the privacy glass are given.

THE DETAILED DESCRIPTION OF THE INVENTION In this detailed description, the subject matter dark colored glass is explained with references to examples without forming any restrictive effect in order to make the subject more understandable.

The components and proportions present in the main composition of a flat glass used in automobile and architecture industries are given in Table 1.

Table 1 : Glass composition

Iron, cobalt, selenium, tin and sodium nitrate are added to the subject matter glass batch, whose main composition is given above, as colorant agents for providing the desired optic properties. The iron in the batch is provided in iron oxide form; and cobalt is provided in cobalt oxide form. Moreover, sulphate is used against the affination problem met in glass production. Zinc selenide is used as the selenium source. Cobalt provides blue color to glass and shows very strong absorption in the visible region wavelength range 530 nm- 590 nm and 650 nm. This decreases visible transmission and solar transmission value, since solar transmission can be calculated in the 350 nm-2100 nm wavelength range. Cobalt is in divalent ionic form normally in soda-lime-silica glass or in other glasses.

Selenium decreases transmittance of glass. The melting point of selenium providing pink color to soda-lime-silica glasses by means of the absorption band centered at 490 nm wavelength in neutral or light oxidant conditions is 217 °C and the boiling point thereof is 685 °C, and therefore, 70-90 % of selenium given to the furnace together with the batch vaporizes during melting.

If the furnace atmosphere is excessively reduced, this will lead to iron selenide complex formation giving undesired brownish pink tone to the glass, and this has to be taken into consideration. On the other hand, in the excessive oxidant conditions, it is in uncolored form. Moreover, since sulphate, added to the batch as the affination substance, is used as oxidant material at the same time, the increases in sulphate amount decrease the selenium retention. If the selenium amount in the batch decreases, this has a negative effect particularly on the transmittance and color of glass which are among the desired optic properties. Iron is provided in Fe⁺² (ferrous) and Fe⁺³ (ferric) forms in soda-lime glasses. Fe⁺² provides blue-green color to the glass and Fe⁺³ provides yellow-green color to the glass. The color provided by Fe⁺² to the glass is 10 times stronger than the color provided by Fe⁺³ provided that they are in the same concentration. Fe⁺² has a strong absorption centered at 1050 nm wavelength in the infrared region. This absorption band continues up to 500 nm wavelength in the visible region and provides solar control function. Fe⁺³ has absorption band centered at 440-430 and 380 nm wavelengths in the visible region and absorption band continuing in the ultraviolet region.

The concentration of reducing agents added to the glass batch decreases since some of the agents vaporize and some of the agents react due to the increase of the melting duration, and there remains no reducing agent in the glass melting after certain duration. Meanwhile, the partial pressure of the oxygen in the glass melting becomes lower than the partial •' pressure of the furnace atmosphere. When all of the agents are consumed, the partial pressure of the oxygen in the glass melting begins increasing and it is balanced with the partial pressure of the oxygen in the furnace atmosphere. The Fe⁺² concentration forming as a result of this is the present concentration. In order to keep the present iron in Fe⁺² form, redox pair is required whose oxygen affinity is higher than Fe⁺² and having low valence.

Tin is a suitable redox pair (Sn⁺²- Sn⁺⁴) for keeping iron in Fe⁺²form. The standard reducing potential of tin redox pair (Sn⁺²- Sn⁺⁴) is 0.15 eV in aqueous solutions and this value is 0.77 eV in iron (Fe⁺² - Fe⁺³). From here, it is seen that Sn⁺² ions have more oxygen affinity than the Fe⁺² ions.

The redox reactions in the glass take place depending on diffusion and this diffusion occurs in a very slow manner since the glasses are viscous. During cooling of the glass, the Sn⁺² - Sn⁺⁴ balance tends to Sn⁺⁴form as a result of the thermal process realized at low temperature. Thanks to the low reduction potential, Sn⁺² ion gives two electrons to the Fe⁺³ ion existing in the ambiance, and is transformed into Sn⁺⁴form, and reduces the Fe⁺³ ion to Fe⁺²form. The reaction related to the subject is given below.

Sn⁺² + 2 Fe⁺³→ Sn⁺⁴ + 2 Fe⁺²

Therefore, tin oxide is added into the glass in order to reduce iron oxide and in order to decrease transmittance in the infrared region. In relation to this, experiments, with and without Sn0₂ in different proportions, are realized in two different iron oxide levels. The results are given in Table 2. As can be seen in Table 2, the increase in tin oxide reduces iron.

Table 2: Effect of different tin oxide increase in fixed iron oxide amount

Selenium is added to the batch together with cobalt oxide in order for the glass to be in grey tones. Because of the volatility of selenium, the addition amount of selenium to the batch and the remaining amount thereof in the final product are important. The decrease of volatility of selenium is an important factor in obtaining a more stable color in glass. In the present invention, it is observed that the tin addition used for reducing iron decreases the volatility of selenium provided in glass batch and observed that tin addition increases selenium retention in the glass surprisingly. Thus, tin addition affects in a positive manner in obtaining pinkish grey tones which is the desired glass color.

In order to obtain the desired optic properties, experiments with anthracite or with tin comprising different amounts of selenium are realized, and Se % retention analyses in glass are realized depending on wet chemistry (Analytical Chemistry) analysis.

Table 3: Batches for different experiments

Raw

Exp.1 Exp.2 Exp.3 Exp.4 Exp.5 Exp.6 materials

Sand 68.7 68.2 68.7 68.2 68.45 68.45

Feldspar 3.78 3.78 3.78 3.78 3.78 3.78

Limestone 2.32 2.32 2.32 2.32 2.32 2.32

Dolomite 21.5 21.5 21.5 21.5 21.5 21.5

Soda 22.56 22.56 22.56 22.56 22.56 22.56

S.

1.10 1.10 1.10 1.10 1.10 1.10

Sulphate

Hematite 1.335 1.335 1.31 1.31 1.31 1.31

Sodium

0.5 0.5 0.5 0.5 0.5 0.5 Nitrate

Cobalt

Oxide - - 0.0250 0.0250 0.0250 0.0250 (CoO )

Zinc

Selenide 0.0162 0.0162 0.0443 0.0443 0.0122 0.0366 (ZnSe03)

Anthracite 0.040 - 0.040 - - -

The amounts of selenium entering into the batch among the given zinc selenide amount are given in Table 4. At the same time, the selenium analyses of glasses obtained in said experiments are realized by wet chemistry, and the duration of remaining of selenium in the glass is detected. The results are again given in Table 4.

Table 4: Se % Retention in the glass according to the wet chemistry analysis

Selenium analysis is realized by means of the wet chemistry method in order to be able to determine the selenium amount in the glass in a more correct manner. The selenium retention is given in Table 4. The first point attracting attention in this table is that selenium retention is low in experiments with anthracite. Experiment 1 and experiment 3 are experiments with anthracite and without tin, and the selenium retention in these experiments is respectively 6.1 % and 4.2 %. In the 2., 4., 5. and 6. experiments without anthracite and with 1 % tin, selenium retention changes between 16.7 - 28 %. The effect of tin addition on the selenium retention in glass is seen in Table 4 particularly between Experiment 1 and Experiment 2 and between Experiment 3 and Experiment 4 in a clear manner. Although equal amount of Se enters into the batch in Experiment 1 - Experiment 2 and in Experiment 3 - Experiment 4, Se retention in batch with tin is higher. Besides, as can be seen in Experiment 4, 5, 6, as the amount of Se entering into the batch changes, the Se retention in the glass, which is the final product, is changing.

Table 5: Transmittance values (Glass thickness 4 mm)

When Table 5 is examined, it is seen that the transmittance values of experiment 1 and 2 are higher when compared with the other glasses. This results from the fact that both glasses do not comprise CoO having high absorption in the visible region. In the first two experiments, in order for the selenium retention to be seen in a clear manner, the experiments are realized without adding cobalt oxide. Moreover, since experiments 1 has anthracite, the selenium retention in the batch decreases, less selenium is found in the chemical analysis of said glass when compared with experiments 2 with tin and without anthracite. As a result of this, experiments 1 passes more light since the selenium absorption is low. Experiment 3 and 4 are repeated by adding CoO to experiment 1 and 2 and by increasing selenium amount. The same result is taken in the experiments with cobalt. In the experiments with tin and without anthracite, the selenium retention is higher when compared with the experiment with anthracite and without tin. Experiment 5 and 6 are repeated by means of different selenium amounts without anthracite and with tin. The selenium retention confirms Experiment 2 and 4, and is observed to have similar values.

As a result, in the experiment with anthracite, zinc selenide is more volatile when compared with the experiments with tin, and the selenium retention in experiments with tin is higher. In the experiments with tin, since selenium is more in batch and since iron is reduced, the transmittance of the glass is lower. Thus, glass passes the heat and light, coming from the outer ambient, less to the inner ambient, and glass provides the ambient temperature to be low and thereby decreases the amount of energy used for cooling the ambient. This ^■* decreases the air-conditioner usage which is preferred for cooling the inner space of vehicle in summer.

As a result of the experiments realized above, the addition amounts of the colorant agents in batch, used for obtaining 11-25 ppm Selenium in the final product glass, are given in Table 7.

Table 7: Colorant additives

In the preferred application, CoO amount is 250 ppm, Fe₂0₃ amount is 1.40 % in weight, and the tin amount is between 0.5-1 %. Moreover, sodium nitrate added to the batch in the proportion range 0.3-0.5 (kg/100 kg glass) supports the glass color to be more stable. In the preferred application, sodium nitrate in proportion of 0.3 is used.

Besides, the amount of selenium entering into the batch as can be seen in Table 4 is 50-150 (ppm/100 kg glass) from ZnSe0₃ added to the batch as the selenium source in proportions given in Table 6, and the remaining amount in the glass after heat process is 11-25 (ppm/100 kg glass). The transmission values of glass in the thickness range of 2 mm - 6 mm comprising the additives in the proportions given in Table 7 are given in Table 8 and Table 9. Table 8: (Se: 25 ppm) Transmittance of glass with tin between 2 mm - 6 mm thickness

Table 9: (Se: 11 ppm) Transmittance of glass with tin between 2 mm - 6 mm thickness

The color analysis results of a glass comprising selenium and tin oxide in 4 mm thickness are given in Table 10.

Table 10: L-a-b values of glass with 4 mm thickness

Tin oxide is not volatile since it has a stable structure and thus supports the stability of production. At the same time, from the studies realized, it is clearly seen that tin addition increases selenium retention in glass more than anthracite, and thus, glass color can be obtained in pinkish grey tones as given in the color analysis results in Table 10. Moreover, the standardization problem faced in productions with anthracite which may exist in various particle sizes in every usage is not faced in production with tin which may be used in close particle size range in every usage. Additionally, since tin oxide does not volatilize from the body even if the particle size is various, it has a positive effect on selenium retention.

The protection scope of the present invention is set forth in the annexed Claims and cannot be restricted to the illustrative disclosures given above, under the detailed description. It is because a person skilled in the relevant art can obviously produce similar embodiments under the light of the foregoing disclosures, without departing from the main principles of the present invention.

Claims

1. A privacy glass having thickness in the range of 2 mm - 6 mm and having low transmitssion, preferably for use in vehicles, and comprising the main composition whose component proportions are given below and comprising selenium in the range of 11-25 ppm in the glass, which is the final product, in order to provide color in grey tones to the glass by being used together with cobalt oxide:

and comprising the following colorants in weight:

characterized by comprising tin oxide in the range of 0.05-1.0 % in weight reducing Fe⁺³, obtained from iron oxide, to Fe⁺² and increasing selenium retention, when compared to glass without tin, in the privacy glass which is the final product.

A privacy glass according to Claim 1 , characterized by comprising tin oxide in range of 0.5-1 % in weight.

A privacy glass according to Claim 1 , characterized in that "L" value of said privacy glass is minimum in the range of (48.1) - (52.2); value "a" is between (-7.90) - (-5.98) and value "b" is between (-4.47) - (+3.97).

4. A privacy glass according to Claim 1 , characterized in that the visible transmission value (Tv) of said privacy glass is minimum 7.5 % and maximum 43 %.

5. A privacy glass according to Claim 1 , characterized in that the solar transmission value (Te) of said privacy glass is minimum 5 % and maximum 34 %.

6. A privacy glass according to Claim 1, characterized in that the transmission value (Tuv) of said privacy glass measured in the ultraviolet region is lower than 11 %.

7. A privacy glass according to Claim 1 , characterized in that the transmission value (Tuv) of said privacy glass measured in the ultraviolet region is lower than 8 %.

8. A privacy glass according to Claim 1 , characterized by comprising 250 ppm CoO in weight.

9. A privacy glass according to Claim 1 , characterized by comprising 0.3 (kg/100 kg glass) NaN0₃ in weight.