WO2020046096A1 - Neutral grey glass having low light transmission - Google Patents

Abstract

The present invention describes an obscure grey glass with a silicon-sodium-calcium composition and a colouring agent, which comprises in percentages by weight: Fe2O3 1.20-3.0%, iron (II) oxide 15-40%(reduction percentage), FeO 0.25-1.0% (expressed as Fe2O3), Co3O4 0.020-0.040%, Se 0.0015-0.010%, CuO 0.00050-0.050% and TiO2 0.01-1%. In addition, the use of colouring compounds such as oxides of nickel, chromium, manganese or rare earth metals is prevented. This glass exhibits low transmission of illuminating light A (TLA) not greater than 20%, preferably not greater that 25%; a transmission of direct solar energy (TDS) not greater than 14%; a transmission of near infrared radiation (TIR) not greater than 14%; a transmission of ultraviolet radiation (TUV) not greater than 8%; a transmission of total solar energy (TTS) not greater than 38%; a purity not greater than 50%; and a dominant wavelength of 480-590 nm when there is a thickness of 2.85-3.85 mm.

Description

 NEUTRAL GRAY GLASS OF LOW TRANSMISSION OF LIGHT

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

 The present invention relates to a glass with low transmittance, neutral gray color and more specifically to a gray glass composition to produce the glass for use in the automotive industry, for the manufacture of panoramic roofs, medallions and rear doors, both laminated as temperate.

 BACKGROUND OF THE INVENTION

 Colored glass is a material which, during the melting process, metal oxides are incorporated. As a result of previous research, it is known that the addition of iron-cobalt oxides in combination with selenium, gives the glass shades from greenish gray - neutral gray to yellowish gray depending on their relationship. By increasing the concentrations of iron oxide, cobalt oxide and selenium and controlling the conditions of oxide-reduction in the melting atmosphere of the glass and / or in the mixture (concentration of carbon and sodium nitrate mainly), a glass with Low light transmission, good blocking of direct solar transmission and the gray color of privacy, which is widely used in roofs, medallions and rear doors of motor vehicles.

 Solar control is the ability to modify the amount of solar radiation transmitted or reflected, in the near ultraviolet spectral intervals (UV; 300-

380 nm), visible (VIS; 380 - 780 nm) and infrared (IR; 780 - 2500 nm). In its automotive use. this is achieved with the addition of several absorbent coloring agents in the initial mixture, so that the glass has properties to absorb both infrared (IR) and ultraviolet (UV) solar radiation, to reduce the passage of excessive heat into the vehicle caused by radiation from the sun, as well as to protect the interiors of the degradation of UV radiation from it.

 The glasses described in almost all patents that refer to a type of neutral gray glass are based on three main dyes: iron oxide, cobalt oxide

V selenium, whose main function is to grant solar control properties to glass.

 The following prior art patents use various metal oxides as main dyes to obtain a gray glass and provide the final characteristics of the product. These components, such as nickel oxide, manganese oxide, chromium oxide or rare earth oxides, are mixed in a base formulation of a silica-sodium-calcium glass.

 For example, the US Patent. No. 5,352,640 (US RE37,998 E) of Combes et al. mentions the obtaining of gray glass used mainly in the automotive industry, whose composition of coloring agents ranges from 1.4 to 4% of iron oxide

(FezOg) and 0 to 0.05% cobalt oxide, with a surplus of cobalt oxide around 0.02% when FeaOa is less than 2%, optionally you can have a combination of CoO + Se + CrzOg with a lower content at 0.24% by weight. The physical properties of the glass such as light transmission and energy transmission are equal to or less than 20% under illuminant A and equal to or less than 12% in a thickness of 3.85 mm, respectively.

In US Patent No. 5,545.5% of Alvarez Casariego, et al, the use of dyes in concentrations of 0.45 to 2.5% for FezOg (total iron) is mentioned, from 0.001 to 0.02% for CoO, from 0 to 0.0025% for Se and from 0 to 0.1% for Cr20g, for gray glass with light transmission with illuminant A of 20 to 60%, used in side and rear windows for vehicles.

US Patent No. 7,393,802 B2 of Seto, et al, describes the use of Fe ₂ O ₃ , CoO, Se and NiO as colorants, but also adds the use of Ce02 and TIO2 in amounts not greater than 2.0% by weight to increase ultraviolet absorption

 For the glasses obtained in US Patent No. 7,622,410 assigned to

Longobardo et al, nickel oxide is used in concentrations of 500 to 1000 ppm, erbium oxide of 0.1 to 0.8% and chromium oxide in contents of 1 to 20 ppm, in addition to a total iron oxide content of 0.15 to 0.45%, selenium less than or equal to 3 ppm and cobalt oxide from 120 to 240 ppm. The mixture of these oxides is used for the general adjustment of the gray color of the glass. The glass light transmission of this patent is 8 a

25%, with a dominant wavelength of 435 to 570 nm, using a cobalt oxide / nickel oxide ratio of 0.22 to 0.30 and FeO / Fe20g redox values of 0.20 to 0.40.

 The main disadvantage of these glasses is the high cost of using rare earth oxides in their composition.

In US Patent No. 8,017,538 B2 of Teyssedre, et al, the glasses presented are known to use nickel oxide in concentrations of 400 to 700 ppm or 1500 to 1900 ppm, iron oxide 0.7 to 0.95% with a redox value of 0.40 or less, in addition to cobalt oxide of 200 to 300 ppm, to obtain an adjustment in the gray color and obtain the following physical properties: light transmission under Illuminant A (TLA) of 50% or less and an average in the power transmission (TE) less than 45%, for a glass of 3.85mm thickness. The use of nickel oxide, used as a colorant in some of the previous patents, has the disadvantage that inclusions of nickel sulphide (defect that is not readily detectable) can be formed that can cause glass sheets to break due to to the difference in the coefficient of thermal expansion of this material with the rest of the vitreous matrix.

 The glasses described in US Patent No. 8,551,899 of Kim, et al., Have a dark gray-green neutral color, given by the dyes used such as FeaOg in 1.4 to 2.5%, CoO of 0.02 to 0.04%, Se from 0.0001 to 0.004%, MnO from 0.005 to 0.5 and CeO from 0.05 to 1% with a light transmission A less than 15%. These glasses are used as privacy glasses or panoramic roofs in cars, as well as used in construction.

 US Patent No. 7,754,632 Delmotte, etal, employs concentrations of MnO up to 600 ppm and TiOz less than 0.1% in addition to other oxides such as

FeaOa 1.1 to 1.5% (total iron), Co 150 to 200 ppm, CraOa 25 to 100 ppm and Se 10 to 50 ppm, to achieve optical transmission characteristics of illuminating light A less than 20% for thicknesses of 4 mm.

 US Patent No. 8,785,338 of Tsuzuki, et al refers to a composition of a silica-sodium-calcium glass with contents of 0.70 to 1.70% by mass of

FezOa (total iron), 0.15 to 0.45% by mass of FeO (ferrous oxide), 0-0.8% by mass of TiOz, 100 to 350 ppm of CoO, 0 to 60 ppm of Se, 100 to 700 ppm of CrzOa and 3 at 150 ppm of MnO, which has a ratio (Fe ²⁺ / Fe ³⁺ ) of ferrous ion to ferric ion of 0.20 to 0.80. This patent claims that this glass has superior ultraviolet radiation absorption and infrared radiation absorption performance (thermal insulation performance). in addition to adequate transparency, achieved thanks to the use of ΊΊO2 preferably in ranges from 0 to 0.5%.

 US Patent No. 9,120,695 Lee, et al., Presents the composition of the following glass: 1.4 to 2% FeaOa with a FeO content of 10 to 30% (with respect to total iron), 0.02 to 0.035% CoO, 0.0015 to 0.004% of Se and 0.005 to 0.5% MnO. Optical characteristics of illuminating light transmission A of less than 15% and ultraviolet light transmission of 2% or less are reported.

 Dark green glasses of US Patent No. 9,617,182 to Cho, et al. (April 11, 2017), use 1.2 to 2% of total FezOa as a dye, 0.0220 to 0.04% of

CoO, 0.002 to 0.0035% of Se and 0.01 to 0.04% of CriOa, in which the weight ratio of

(CoO + Cr ₂ O ₃ ) a Se (= [CoO + Cr ₂ O ₃ j / Se) is 13 to 25 and the weight ratio of CoO to CrzOa (=

CoO / CraOa) is 0.9 to 1.8. The glass shows a visible light transmittance (TLA) of 15% or less, a direct solar energy transmittance (Cough) of 16% or less and an ultraviolet radiation (Tuv) transmittance of 3% or less, measured for a thickness 4 mm reference.

US Patent No. 7,902,097 B2 of Gd-Aguilar et al., Uses concentrations of: 0 to 30 ppm of C03O4, 1 to 20 ppm of Se, 20 to 200 ppm of CuO and 0.30 to 0.70% of FezOa to obtain a glass neutral gray, with optical characteristics of light transmission with illuminant A greater than 65%, total solar energy transmission equal to or less than 60%, ultraviolet radiation transmission less than 46% and a dominant wavelength of 490 to 600 nm . This patent adds components such as 0.01 to 0.07% carbon or 0.2 to 1.2% sodium nitrate for the modification of the oxide-reduction state of iron and copper oxide, since, in combination with the other dyes, it is used as an alternative to obtain the gray hue, partially replacing the addition of titanium oxide and cobalt oxide.

As can be read from the above, the iron is present in the glass (silica-sodium - calcium) into two compounds depend on the oxidation state of iron: if iron is present as Fe ^2+, the formed composite oxide is ferrous (Ugly). If the iron is as Fe ^3+, ferric oxide (FezOs) would be found. Each ion confers different properties; Ferrous ion has a broad and strong absorption band centered at 1050 nm, which results in a decrease in infrared radiation. In addition, this band extends towards the region of the visible, decreasing the transmission of light and imparting a bluish color in the glass. On the other hand, the ferric ion has a strong absorption band located in the ultraviolet region which obviously prevents its transmission through the glass and, in addition, it has two other weak bands in the visible region located between 420 and 440 nm, which cause a slight decrease in light transmission and a yellowing of the glass.

Generally, the iron in the glass and its amount of ferrous oxide are expressed in the form of Fe ₂ O ₃ . Being common in the industry to express the amount of ferrous or ferric oxide as the percentage of total iron. The balance between ferrous and ferric oxide has a direct effect on the characteristics of the color and transmittance of the glass, represented as:

This means that the greater the amount of ferric ion (Fe ³ *) present in the glass, the greater the absorption of ultraviolet radiation and the light transmission will increase; as well as the yellowish hue; but, if the content of the ferrous ion (Fe ² *) increases as a result of the chemical reduction of Fe2Ü3, the absorption of infrared radiation will increase, but the absorption of ultraviolet radiation will decrease and as will the transmission of light.

 The variation of the FeO concentration in relation to FeaOs, results in a color change in the glass. The displacement of the hue can be modified from yellow to green, blue to amber. The color changes as follows

(according to experimental results):

 Yellow— Low ferrous (12%) - High light transmission (High ferric ion)

 Yellow-Greenish (16%)

 Green-Yellowish (20%)

 Green (25% typical green glass value)

 Bluish Green (29%)

 Greenish Blue (35%)

 Blue (50%)

 Olive Green (60%)

 Champagne (65%)

 Amber— High ferrous (75%) - Low light transmission (low ferric ion)

To control the balance between ferrous oxide and ferric oxide necessary to achieve a solar control glass, it is necessary to establish the conditions in mixture and melting atmosphere; For the first case, the concentration of reducing agents such as carbon and oxidizing agents, such as sodium sulfate and sodium nitrate, is adjusted. For the Regarding melting conditions, it is necessary to adjust the atmosphere with more or less oxygen content depending on the thermal performance and hue of the desired glass.

 Additionally, it is well known that titanium oxide also acts as a dye and when used in combination with FeaOs, it is possible to obtain a further reduction in the transmission of ultraviolet radiation to a point where the desired visibility transmission is achieved.

 K. M. Fyles in the article Modern Automotive Glasses, Glass Technology, vol 37,

February, 1996, pp. 2-6, considers that iron is the most important dye in automotive glasses since it is a low-priced component that absorbs undesirable ultraviolet radiation (ferric ion) and, in addition, in large quantities infrared radiation (ferrous ion) .

 Gordon F. Bresterm et al, in the article "The color of iron-containing glasses of varylng composition", Journal of the Society of Glass Technology, New York, USA, April, 1950, pp. 332-406, mentions the color changes caused by systematically varying the composition of the iron-containing silicate and the silica-free glasses evaluated in terms of visual color, spectral transmission and chromaticity.

 Other articles also describe the importance of the balance between ferrous and ferric oxides in glasses such as that written by N. E. Densem; The equllibrium between ferrous and ferric oxides in glasses; Journal of the Society of Glass Technology, Glasgow,

England, May 1937, pp. 374-389; J. C. Hostetter and H. S. Roberts, "Note on the dissociation of Ferric Oxide dissolved in glass and its relation to the color of iron-bearing glasses";

Journal of the American Ceramic Society, USA, September, 1921, pp. 927-938. Many books and scientific articles have been published on the composition of colored glass with characteristics of absorption of infrared and ultraviolet radiation.

 C.R. Bamford, in the book Color Generation and Control in Glass, Glass Science and

Technology (Elsevier Science Publishing Co., Amsterdam, 1977) describes the principle of methods and applications about glass coloring. In this book the author considers that three elements govern the color of the light transmitted by a glass, being the color of the incident light, the interaction of the glass with that light and the interaction of the light transmitted with the eye of the observer. The procedures require the spectral transmission data of the glass with the corresponding glass thickness and viewing angle.

With respect to titanium oxide (TiOz) in silica-sodium-calcium glasses, the most stable form of titanium in glasses is tetravalent (Ti ⁴ *). The trivalent form could confer coloration, however, this effect is not observed in the silica-sodium-caddy glass. In the document "Effects of titanium dioxide on glass" written by Beals MD, The Glass Industry, September, 1963, pp 495-531, describes the interest that titanium dioxide has been shown as a glass component. The effects produced by the use of titanium dioxide include comments that TiOz greatly increases the refractive index, increases the absorption of light in the ultraviolet region, and that viscosity and surface tension are reduced. From the data on the use of titanium dioxide in enamels, it was observed that TiOz increases chemical durability and acts as a flux. In general, clear glasses containing titanium dioxide can be found in all common glass forming systems (borates, silicates and phosphates). The different regions of glass formation for systems containing titanium dioxide are not grouped in one place, since the organization of the discussion It is based more on the properties of a use of glasses containing titanium dioxide rather than its own constitution.

 On the other hand, the addition of selenium to the silica-sodium-calcium glass can produce a pink color due to the presence of atomic selenium. Selenium is one of the most widely used physical bleach for glass with traces of iron coming as an undesirable impurity in raw materials, because its coloration neutralizes the ferrous and ferric ions present in the glass.

 The combination of iron oxide and selenium in the silica-sodium-calcium glass confers a reddish-brown color and a decrease in light transmission, due to an absorption band located in the visible region between 490 and SOOnm (selenium-like band atomic). This band extends to the ultraviolet region, also causing a decrease in this type of transmission in the glass.

 The intensity of the coloration and the final properties of the glass are a function of the concentration of iron oxide and selenium in the glass.

 It is well known that copper has played an important aspect in the production of glass, ceramics and colored pigments. It has been recognized, for example, the coloring of Persian ceramics for its hue conferred by copper. Of special interest to ceramic artists, they are turquoise blue and especially dark Egyptian blue and

Persian (Waldemar A. Weil; Colored Glasses, Society of Glass Technology, Great Bretain, P.154-167, 1976).

Copper has been used in glass compositions, not only in those of the silica-sodium-calcium type, but in some others, such as those containing for example borosilicate Therefore, the color developed depends on the base of the glass, its concentration and its oxidation state.

 In the case of a sodium-silica-calcium base glass, copper in the form of oxide imparts a blue coloration of a greenish hue, specifically turquoise, however, in the glass, copper can be in its monovalent state, which does not imparts color Thus, the greenish blue coloration depends not only on the amount of copper present, but on the ionic balance between the cuprous and cupric states. The maximum absorption of copper oxide is in a band centered at 780 nm and a secondary weak maximum peak is present at 450 nm, which disappears at high soda contents (about 40% by weight) (CR Bamford Color Generation and Control in Glass, Glass Science and

Technlogy, Elsevier Scientific Publishing Company, P. 48-50, Amsterdam, 1977).

 The incorporation of copper oxide (CuO), in combination with iron oxide, cobalt oxide, selenium and titanium oxide is as an alternative to obtain a gray shade of low light transmission for use in the automotive industry or of the construction, where a low light transmission glass A (TLA) of not more than 15% is required, a direct solar energy transmission (Cough) not greater than 14%, a near infrared radiation transmission (Tm) does not greater than 14%, a transmission of ultraviolet radiation (Tuv) not greater than 8%, a transmission of total solar energy (TTS) not greater than 38%, a purity not greater than 50% and a dominant wavelength of 480- 590 nm when it has a nominal thickness of 3.85 mm.

It has been proven that in industrial production it is feasible to add CuO at concentrations less than 120 ppm for a thickness of 4 mm and less than 100 ppm for thicknesses of 6 mm. Glass can also be manufactured in smaller thicknesses such as glass used in the manufacture of laminated systems. If higher concentrations of CuO are present, during the formation process within the float chamber, a reduction process attributable to the process atmosphere could occur, presenting a reddish coloration on the glass surface, which is observed by reflection. This effect is related to the residence time and the forward speed of the glass strip, which means that, at lower speeds, it will be necessary to reduce the content of CuO in glass or adjust the reducing conditions in the float chamber.

OBJECTIVES OF THE INVENTION

 A main objective of the present invention is a gray glass of low light transmission A (Tu) not greater than 15%, a direct solar energy transmission (Cough) not greater than 14%, a near infrared radiation transmission (Tm ) not exceeding 14%, a transmission of ultraviolet radiation (Tuv) not exceeding 8%, a transmission of total solar energy (TTS) not exceeding 38%, a purity not exceeding 50% and a dominant wavelength of 480-590 nm when it has a nominal thickness of 3.85 mm, manufactured by the float process.

Another objective of the present invention is the use of copper oxide as a partial replacement of cobalt oxide (C03O4). The feasibility of its addition in flat glass manufactured by the float process to levels close to 120 ppm without reduction effect due to the conditions of the tin chamber is demonstrated. Likewise, T1O2 is incorporated as an additional element to iron oxide to provide a supplementary reduction in the transmission of ultraviolet radiation. A further objective of the present invention is also to obtain a gray glass composition of low light transmission, including additional elements such as carbon or sodium nitrate to modify the oxide-reduction state of iron oxide.

The glass of this invention avoids the use of coloring compounds such as nickel, chromium, manganese or rare earth oxides, mainly erbium oxide (Er ₂ Ü3).

DETAILED DESCRIPTION OF THE INVENTION

 The present invention relates to a gray glass composition that, even when its use in the automotive industry is mentioned as its main application, is not limited to its use in other fields such as the Construction Industry or other applications such as, for example, It can be used as a substrate to be coated by one or thin muticapas applied via vacuum cathodic erosion process (MSVD), chemical vapor reservoir (CVD) or other techniques.

 The typical composition of a silica-sodium-calcium glass formed by the float glass process for the automotive industry, is characterized by the following formulation based on the percentage by weight with respect to the total weight of the glass:

S0₃ 0.05 a 0.3

S0 ₃ 0.05 to 0.3

 The glass composition of this invention is based on a silica-sodium-calcic glass to which the following dyes were added, to obtain a gray color:

 Components% Weight:

The main objective of adding sodium nitrate (NaNOa) and carbon to the composition is to modify the oxidation state of iron to reach the optimum level of direct heat transmission (Cough).

This gray glass has a light illumination transmission A (TIA) not greater than 15%, a direct solar energy transmission (Cough) not greater than 14%, a near infrared radiation transmission (½) not greater than 14%, a ultraviolet radiation (Tuv) transmission not exceeding 8%, a total solar energy transmission (TTS) not exceeding 38%, a purity not exceeding 50% and a dominant wavelength of 480-590 nm when it has a thickness by example between 1.4 to 6mm, 1.6 to 5mm, and more preferably 3.85mm. The glass of this invention avoids the use of coloring compounds such as nickel, chromium, manganese or rare earth oxides, mainly erbium oxide (EraOa).

 The following examples show the physical properties, of illuminating light transmission A (TLA), direct solar energy transmission (Cough), near infrared radiation transmission (½), ultraviolet radiation transmission (Tuv), total solar energy transmission ( TTS) The color transmission (L *, a * and b *), color purity and a dominant wavelength (l), for a glass of 3.85 and 2.85 mm thick.

 Table 1 and 2

 Tables 1 and 2 (examples 1 to 14) show the experimental results of the composition of the present invention with the combination of iron oxide (FeaOa), cobalt oxide (C03O4), selenium (Se), copper oxide and titanium oxide (T1O2). In addition, they contain 0.66% sodium nitrate ^ NaNOa) as an oxidizing agent in the mixture, without the addition of carbon.

TABLE 1

Tabla 3

Table 3

 Table 3 (examples 15 to 18) shows the experimental results of the composition of the present invention with the combination of iron oxide (FeaOs), cobalt oxide (C03O4), setenium (Se), copper oxide and oxide of titanium (T1O2). In addition, it is incorporated

0.16% sodium nitrate (NaNOa) and 0.04% carbon (coke type) in the mixture.

Table 4 and 5

 Tables 4 and 5 (Examples 19 to 31) show the experimental results of the composition of the present invention with the combination of iron oxide (Fe203), cobalt oxide (C03O4), setenium (Se), copper oxide and titanium oxide (TiOz). They also contain

0.16% sodium nitrate (NaNOa) and 0.02% carbon in the mixture. 5

Table 6

Table 6 (Examples 32 to 34) shows the experimental results of the composition of the present invention with the combination of iron oxide (FezOg), cobalt oxide (C03O4), selenium (Se), copper oxide and oxide Titanium (UNCLE2). In addition, they contain 0.16% sodium nitrate (NaNOg) and 0.030% carbon.

 The main objective of adding sodium nitrate (NaNOa) and carbon to the composition is to modify the oxidation state of iron to reach the optimum level of direct heat transmission (Cough). Color and privacy are adjusted by optimizing the percentages of dyes written in this invention.

The physical properties of the glasses obtained were evaluated in accordance with internationally accepted standards. The specifications for the determination of ales color, such as the dominant wavelength and the excitation purity, have been derived from the Tristimulus altitudes (X, Y, Z) that have been adopted by the International Commission of Illumination CIE), as a result Direct experiments involving many observers. These specifications can be determined by calculating the trichromatic coefficients, and, z of the Tristimulus values corresponding to the colors red, green and blue spectively. The trichromatic values are plotted in the aromaticity diagram and Accompanied with the coordinates of the illuminant D65, considered as a lighting standard. The comparison provides the information to determine the purity of color excitation and its dominant wavelength. The dominant wavelength defines the color wavelength and its value is in the visible range, from 380 to 780 nm, while for excitation purity, the lower its value, the closer it tends to be a neutral color

The calculation of the transmission of ultraviolet radiation (Tuv) is adjusted to the radiation range

Solar UV, so it was evaluated in the range of 300 to 400 nm in 10 nm intervals, as indicated in ISO / DIS 13837.

For the evaluation of the light transmission, the illuminant "A" (T _LA ) was used, in the wavelength range of 400 to 800 nanometers, integrating values in 10 nm intervals. The color transmission (L *, a * and b *) was calculated according to ASTM E308 (CI D65 observer at 10 ”).

 The values of the direct solar energy transmission (Cough) were evaluated in the range of

300 to 2500 nm with intervals of 5, 10 and 50 nm, in accordance with ISO / DIS 13837.

In the infrared (T _IR ) transmission, the range of solar spectrum radiation is contemplated, having a range of 800 to 2500 nm, with 50 nm intervals, using the values of ISO / DIS 13837.

The total solar energy transmission (TTS) was evaluated in the range of 300 to 2500 nm considering wind speed of 4 m / s (parked), in accordance with ISO / DIS 13837.

The neutral gray glass of this invention can be manufactured by the float glass process from a thickness of 1.4 mm to 6 mm, however, it is not limited only to this range of Thicknesses and can be processed as tempered, in double-sided windows, laminated friction systems or as a substrate covered by one or more layers.

 This glass has the following properties: light transmission with ATLA illuminant) not greater than 15%, direct solar energy transmission (Cough) not greater than 14%, near infrared adiation transmission (TIR) not greater than 14%, transmission of ultraviolet radiation (Tuv) not greater than 8%, total solar energy transmission (Trs) not greater than 38% and purity not greater than 50%.

 From the foregoing, a composition of neutral gray glass of low transmission and light has been described and it will be apparent to those skilled in the field that other possible improvements can be made, which may be considered within the field determined by the following claims.

Claims

EIVINDICATIONS 1. A glass with low transmittance, of a neutral gray color, comprising a composition of sodium-silica-calcium glass and a dye, wherein the dye comprises: ezOa from 1.20 to 3.0%, a% ferrous (% reduction) of 15 at 40%, 0.25 to 1.0% FeO (Express as Fe ₂ O ₃ ), CO ₃ O ₄ from 0.020 to 0.040%, Selenium from 0.0015 to 0.010%, CuO from 0.00050 to 0.050% and TiO ₂ from 0.01 to 1%, wherein the glass has a light illumination transmission A (TLA) not greater than 0%, a direct solar energy transmission (Cough) not greater than 14%, a near infrared death (TIR) transmission not greater than 14%, a ultraviolet radiation transmission, (Tuv) or greater than 8%, and a total solar energy transmission (T _TS ) not greater than 38% with a thickness of .85 to 3.85 mm.  2. The glass composition according to claim 1, wherein said glass is preferably produced in a thickness of 3.85 mm.  3. The glass composition according to claim 1, wherein said glass l glass has an illuminating light transmission A (TLA) preferably not greater than 15%, 4. The glass composition with low transmittance, of neutral gray color according to claim 1, comprising 0.01 to 1.0% NaNO ₃ in mixture  5. The glass composition with low transmittance, of neutral gray color according to claim 1, comprising 0 to 0.07% Carbon in mixture. 6. The glass composition with low transmittance, of neutral gray color according to claim 1, having a dominant wavelength of 480-590 nm, in terms of a nominal thickness of 3.85 mm, obtained by a measurement with an illuminator D65 observer at 10 ” 7. The glass composition with low transmittance, of neutral gray color according to claim 1, wherein the base glass composition comprises: 68 to 75% SIO¾ 0 to% AI2O3, 5 to 15% CaO, 0 to 10% of MgO, 10 to 18% of Na ₂ 0, 0 to 5% of K ₂ 0 and 0.05 to 0.3% and SO3.  8. A glass sheet according to claim 1, which is formed by the float process.  9. The glass sheet of claim 6, which has the following color coordinates measured under the illuminant D65, a * from -10 to 5, b * from -5 to 15. and purification dexcitation not greater than 50% for a thickness of 3.85 mm.  10. The glass composition according to claim 1, wherein said glass is produced with a thickness preferably between 1.2 and 6.0 mm.