Method for assessing the susceptibility of glazing to the formation of quench marks

Abstract

The present invention relates to a method for assessing the susceptibility of a glazing to the formation of quench marks by the anisotropy of said glazing, said susceptibility being determined by the parameter σ V wherein the quench marks are due to different optical phase shifts in different regions of the glazing, in transmission or reflection, and for viewing from either side of the glazing, - a computer-implemented calculation step of calculating at least one parameter of transmission through surface 1 or surface 2, called T1 or T2, or at least one parameter of reflection from surface 1 or surface 2, called R1 and R2, said calculation being performed for areas of the glazing without an optical phase shift and for areas of the glazing inducing an optical phase shift δ, a computer-implemented calculation step of calculating, based on at least one of the parameters T1, T2, R1, R2, at least one parameter ΔE(δ) corresponding to the color difference between the areas of the glazing that do not induce an optical phase shift and the areas of the glazing that induce the optical phase shift δ, σ by applying a function G that depends on the one or more calculated ΔE(δ) and, if appropriate, on the one or more corresponding δ. V To calculate The present invention relates to a method, including:

Description

[Technical field]

[0001] The present invention relates to the field of thermally strengthened glasses, in particular to the field of glasses called heat strengthened glasses, also called "semi-tempered" glasses, or heat tempered glasses, and more particularly to the field of such glasses coated with at least one thin layer. [Background technology]

[0002] The glasses to which this patent application relates may be particularly intended for the glazing of architectural curtain walls, urban furniture, and transportation vehicles (cars, buses, trains, boats and ships, airplanes, etc.).

[0003] The processes used to thermally strengthen glass, especially in heat tempering or heat strengthening, include heating to more than 600 degrees, followed by quenching with air jets. For this purpose, the glass is heated in a furnace, especially in a radiant or convection furnace, and then cooled using a cooling device that generally comprises a quench chamber that subjects the glass to multiple air jets emitted through nozzles. In many installations for producing thermally strengthened glass, the glass is conveyed horizontally through a bed of rollers. The speed of the air jets is adjusted depending on the final glass thickness and the stress level desired in the final glass.

[0004] In the context of the present invention, the expression thermally strengthening is a general expression covering thermal strengthening and thermal tempering. Thermally strengthening glass generates a stress field in the thickness of the glass, providing a greater mechanical resistance to bending and, in particular in the case of tempered glass, causing it to break in a specific manner that can reduce the risk of personal injury in the event of breakage. This stress field is due to the difference in cooling rate between the surface of the main face of the glass and the core of the glass as it hardens. The thicker the glass, the less it needs to be blown hard to generate a residual stress field, due to the greater thermal inertia of the core with respect to cooling.

[0005] Generally, the air jets used for cooling are applied simultaneously to both main faces of the glass. They may be blown between the rollers used to transport the glass sheets. The use of air jets does not guarantee a uniform cooling of the entire glass. The use of glasses coated with layers, especially with low-E layers, may further complicate the furnace mechanics. Potentially large inhomogeneities in the temperature field of the glass are observed, and temperature gradients of tens of degrees Celsius are sometimes measured over distances of only a few centimeters when the glass leaves the furnace and is then cooled. Depending on the thermal history and due to the photoelastic properties of the glass, this may cause the appearance of iridescence under polarized light, known to those skilled in the art as "quench marks", "distortion patterns" (in French "marques de trempe", "fleur de trempe") or "leopard spots", and these expressions are also used for heat-strengthened glasses, also called "semi-tempered" glasses. This inhomogeneity of the glass is due to a non-uniform and anisotropic stress distribution inside the glass. This stress distribution depends primarily on the thermal history of the glass, i.e., the non-uniformity of the heating and cooling used to thermally strengthen the glass.

[0006] In order to reduce quench marks in thermally strengthened glass, various solutions have already been proposed, in particular as proposed in WO 2018 / 051029. Summary of the Invention [Problem to be solved by the invention]

[0007] Coatings applied to glass can moderate the appearance of the quench marks, either by accentuating them or by hiding them. Currently, there is no simple means to predict the effect that a coating will have on the quench marks of thermally strengthened glass before it is manufactured, and one subject of the present invention is to fill this deficiency. [Means for solving the problem]

[0008] According to the invention, the quench marks of the glazing are considered to be the result of color differences between various areas of the glazing. Since the cause of these quench marks is stress anisotropy, and since areas of different stress induce different optical phase shifts of the light rays, giving them different colors, the idea was given to establish a metric based on a calculable color difference between areas of the substrate without an optical phase shift and areas of the same substrate that induce a given optical phase shift. This metric allows glazings to be compared for a specific optical phase shift and a specific angle of incidence of the light rays. It is therefore possible to simulate, before their manufacture, glazings that are thermally strengthened under specific conditions, i.e. glazings with areas that induce the same optical phase shift and areas without an optical phase shift. Furthermore, this method makes it possible to evaluate the influence of a coating system on hiding or highlighting the quench marks by comparing a glazing with a coating system with the same glazing lacking the coating system. In the context of the present invention, a coating system is understood to be a coating applied to a single surface of the glazing or a combination of two coatings each applied to different main surfaces of the glazing, the coating being a thin layer or a stack of thin layers.

[0009] The invention is applicable to glazing comprising a glazing substrate, whether or not coated with a thin layer or a stack of thin layers on one or both of its main faces. The two main faces of the glazing are in contact with the external environment of the glazing, for example with the ambient air. The glazing substrate comprises at least one glass sheet. The glazing substrate may be laminated and thus comprise at least two glass sheets separated by an interlayer made of a polymer, for example PVB. The glazing substrate has substantially the same refractive index throughout its thickness. PVB has substantially the same refractive index as glass. In this patent application, the expression "glazing substrate" refers to one or more glass sheets and one or more optional polymer interlayers, but excludes any thin layers. The invention is not applicable to glazing of a glazing substrate containing a thin layer inserted between the two main faces of the glazing substrate (for example laminated glazing comprising a thin layer between one of its glass sheets and the polymer interlayer).

[0010] In the context of the present invention, the optical phase shift observed for an area of ​​glazing is believed to be induced by the glazing substrate it contains, and not by one or more thin layers that may be disposed on this glazing substrate: a thin layer or stack of thin layers only slightly moderates the appearance of the quench mark pattern.

[0011] The invention is applicable to transparent glazing, i.e. glazing that allows visible light to pass through. Any material contained in the glazing (glass, polymer interlayer, lamina) therefore allows visible light to pass through.

[0012] Generally, the thin layer or stack of thin layers has a thickness comprised in the range of 0.5 to 350 nm.

[0013] The thin layer has the following features: anti-reflection, Solar control, Low-E, Prevents condensation, Self-cleaning One or more of the following may be fulfilled:

[0014] The thin layer may be selected from the following list of materials: silver, zinc oxide, silicon nitride, silicon oxide, titanium dioxide, titanium oxide, ITO.

[0015] A quench mark can be likened to a change in color in different areas of the substrate receiving polarized light, as seen by an observer looking at the glazing. The light coming from the glazing and seen by the observer can be the light that has passed through the glazing (in this case referred to as "transmitted") or the light that has been reflected by the glazing (in this case referred to as "reflected"). The quench mark can affect the transmitted light and / or the reflected light. A parameter called color difference, ΔE, is defined, for example, by the International Commission on Illumination (CIE) and is considered to represent the color difference introduced by the quench mark. According to the 1976 CIE formula:

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[0016] In the context of the present invention, the parameter σ for characterizing the tendency of a glazing to exhibit quench marks V This parameter σ Vis based on the determination of the color difference between a point of glazing with no optical retardation and a point of glazing inducing an optical phase shift. V may be independent or only weakly dependent on the optical phase shift induced by the glazing substrate contained in the glazing.

[0017] The present invention relates to a method for evaluating the susceptibility of a glazing to the formation of quench marks by the anisotropy of the glazing, the susceptibility being determined by the parameter σ V wherein the glazing comprises a face 1 and a face 2, both in contact with the external environment, the quench marks resulting in different optical phase shifts in different areas of the glazing, for transmission or reflection and for viewing from either side of the glazing, the method comprising: a calculation step carried out on a computer of calculating at least one parameter of the transmission through surface 1 or surface 2, called T1 or T2, or at least one parameter of the reflection from surface 1 or surface 2, called R1 and R2, said calculation being carried out on the one hand for areas of the glazing which do not induce an optical phase shift, and on the other hand for areas of the glazing which have a birefringence axis oriented at a given angle relative to the plane of incidence and which induce an optical phase shift δ in the light ray within the range of a given optical phase shift, for a given polarization of the light ray and for a given angle of incidence of the light ray, a computer-implemented calculation step of calculating at least one parameter ΔE(δ) corresponding to a color difference between an area of ​​the glazing that does not induce an optical phase shift and an area of ​​the glazing that induces an optical phase shift δ, based on at least one of the parameters T1, T2, R1, R2, then σ by applying a function G that depends on one or more calculated ΔE(δ) and, where appropriate, on one or more corresponding δ V The process of calculating Includes.

[0018] According to the model of the present invention, the optical phase shift δ is independent of wavelength in the visible spectrum.

[0019] Preferably, the angle of the birefringence axis relative to the plane of incidence is 45 degrees and the polarization is s- or p-polarized, as this corresponds to the viewing conditions that result in the most visible quench marks.

[0020] The function G is derived from at least one ΔE(δ) and, where appropriate, the corresponding δ to σ V Calculate σ that is meaningful for the metric. V Therefore, the value of σ V = G(ΔE(δ), δ). This means that, in particular, σ V = ΔE(δ). A given δ corresponds to ΔE(δ). If multiple ΔE(δ) are calculated, each ΔE(δ) is calculated for a different δ.

[0021] The function G is also a function of a σ determined for a given δ. δ or multiple σ determined for different δ δ is equal to any function F2 that depends only on δ is equal to the quotient of ΔE(δ) divided by a function F1(δ) that depends only on the corresponding δ (σ δ =ΔE(δ) / F1(δ)). G=F2(σ δ In particular, the function F2 can be written as δ It may be a polynomial function of

[0022] One or more σ δ It is advantageous for σ to be independent or only weakly dependent on the optical phase shift induced by grazing. V Also, and σ V Therefore, it is more representative of the effect of the coating on the quench mark for a wider range of optical phase shifts. δIn the search for a function F1 that is independent or weakly dependent on the optical phase shift, it is empirically and intuitively found that F1(δ) is advantageously sin 2 The assumption is that F1(δ) may be close to or equal to δ. F1(δ)=sin 2 δ, the smaller the optical phase shift δ, the greater the δ It has been observed that σ does not depend on the optical phase shift δ. For this reason, the range of suitable optical phase shifts in the context of the present invention is preferably close to 0 and starts from 0. In particular, σ as δ approaches 0 δ The limit of is σ to characterize the glazing. V In fact, the quotient ΔE(δ) / sin 2 It has been observed that (δ) is substantially independent of δ, especially for small values ​​of δ (especially for δ<π / 2, especially for δ<π / 15, and especially for δ<π / 30), which corresponds to the most usual case. Of course, functions other than the sine function that return values ​​close to those given by the sine function may be potentially suitable for use as the function F1. For example, the limit expansion of the sine function is generally suitable. To give another example, consider F1=δ for particularly low values ​​of δ, e.g., δ<π / 30. 2 is also sometimes appropriate. For this reason, 2 δ)-1~(sin 2 δ)+1, preferably (sin 2 δ)-0.5~(sin 2 It was deemed sufficient to select F1(δ) that returns values ​​contained in F1(δ)+0.5.

[0023] σ characterizing the glazing V The value of is a single σ for a given value of the optical phase shift. δ or using the respective σ δ are determined for different values ​​of the optical phase shift δ. δ The value σ V is one or more σ δ The function F2(σ δ ) can be used to determine this function F2(σδ ) is optional and allows the glazing to be characterized for any metric. For this metric, σ of the glazing V1 comprising the glazing substrate and the coating system V1 of glazing V2 with the same glazing substrate but lacking a coating system V2 and the coating system enhances the quench marks relative to the plain glazing substrate (σ V1 >σ V2 ) or hide the quench mark (σ V1 <σ V2 ) can be evaluated. Of course, this comparison is carried out with two glazings V1 and V2, using the same metric, and therefore the same value of δ and the same functions G, F1 and F2. It should be noted that the glazing V2 may very well already be provided with a thin layer or a stack of thin layers on one or both of its two main faces, and the coating system of V1 may add a thin layer or a stack of thin layers to the thin layer or stack of thin layers already present on V2. It is therefore possible, prior to the production of the coating system, to simulate the effect that the coating system will have on the quench marks of the glazing, in order to select the most suitable coating system.

[0024] Single σ δ When is determined, the function F2(σ δ ) can be expressed simply as σ δ (σ V = σ δ ). Function F2(σ δ ) is σ δ In particular, the function F2(σ δ ) may be the coefficient of proportionality k (σ V =k σ δ ). Function F2(σ δ ) may be the addition or subtraction of a constant value x.

[0025] Multiple σ δ From σ Vis determined, within a given range of the optical phase shift δ, this function F2(σ δ ) can be expressed as, for example, multiple σ δ , for example, a polynomial function of σ in this range of optical phase shifts δ. δ It may be the arithmetic mean of

[0026] Any function F2(σ δ ) is chosen, the limit of ΔE / F1(δ) as δ approaches 0 (zero optical phase shift) is σ δ is a preferred value of σ because it has been observed that ΔE / F1(δ) becomes less dependent on δ as δ approaches 0. Therefore, it is advantageous to set σ V =F2(lim δ→0 ΔE / F1(δ)). In particular, as δ approaches 0, σ V is simply σ δ In particular, σ V =lim δ→0 ΔE / sin 2 (δ) is particularly suitable.

[0027] The range of the optical phase shift δ is comprised between 0 and π. In general, it is sufficient for δ to be comprised between 0 and π / 2, or even between 0 and π / 15, or even between 0 and π / 30. In practice, for the least sensitivity to changes in δ, the values ​​of δ closest to 0 are the most suitable σ. δ results.

[0028] Preferably, the function F2(σ δ ) is monotonic (monotonically decreasing or increasing) as a function of δ. δ ) is arbitrary and can be freely chosen to generate a metric. δ ) can also be applied by computer.

[0029] σ V To determine σ, we use the σ as a function of δ within the range of δ in the problem starting from 0. δ After confirming that the value of hardly changes, (function F2(σ δ) for small δ, in particular for a single σ corresponding to δ smaller than π / 2 δ Only values ​​of 0 and 1 can be used.

[0030] σ V To determine, we use multiple σ as a function of δ within the range of δ in the problem starting from 0. δ After making sure that the value of seldom changes, we apply (by applying function F2) to several small δs, in particular to several σs corresponding to all δs smaller than π / 2. δ The value of can be used.

[0031] Single σ δ is used or multiple σ δ Regardless of which is used, preferably the range of δ is σ as δ varies from 0 to the maximum value of this range. δ is chosen so that it varies by less than 0.5, preferably less than 0.2. For δ equal to 0, σ δ If it is not possible to determine F1(δ), then F1(δ) is 2 δ), σ at δ=0 δ As the value of δ approaches 0, the limit of ΔE / F1(δ) (lim δ→0 Advantageously, the maximum value of the range for δ is less than π / 15, preferably less than π / 30.

[0032] The iridescence effect of the quench mark depends strongly on the polarization state of the incident light and on the angle of incidence of the light ray on the glazing substrate. Moreover, generally, ΔE is a maximum value for an angle of incidence on the glazing substrate comprised between 50 and 80°, therefore preferably the angle of incidence is selected to be comprised in this range and is in particular set equal to 60°.

[0033] Generally, glazing comprises two faces in contact with the external environment, called face 1 and face 2. Each of these faces has intensity-related transmission and reflection properties that are characteristic of the exterior / interior interface. These properties are expressed by the following parameters: x τ i (θ): Transmission coefficient of surface i (1 or 2) for polarization x (s or p) ext x ρ i (θ): reflection coefficient of external surface i (1 or 2) for polarization x (s or p) int x ρ i (θ): Reflection coefficient of internal surface i (1 or 2) for polarized light x (s or p) Thus, there are a total of 12 parameters to characterize the interface of the glazing with the external environment. All these parameters are wavelength dependent and can therefore be represented by a wavelength-dependent spectrum.

[0034] These parameters τ and ρ, particularly in the case of a lamina or stack of lamina, are both known or can be measured in a manner known to the person skilled in the art, and they can be determined (by measurement or calculation) for any lamina or stack of lamina.

[0035] Based on these interface parameters, the transmission (T1 and T2) and reflection (R1 and R2) parameters of the glazing can be calculated for its two faces 1 and 2. T1 (T2, respectively) is the transmission coefficient of a ray passing through the glazing after hitting its face 1 (face 2, respectively). R1 ​​(R2, respectively) is the reflection coefficient of the glazing for a ray hitting its face 1 (face 2, respectively).

[0036] In general, after each pass through the glazing, and in particular after each reflection from an internal interface, the polarization state changes. In the specific case where the incident beam is polarized with polarization x (s or p polarization), the birefringence axis of the substrate is oriented at 45° to the plane of incidence, and the phase shift can be expressed as a fraction of π: δ=π / n (π / 2, π / 3, π / 4, ...), the beam is again polarized with polarization x after 2n reflections. Coefficients of internal reflection and transmission k τ i and int k ρ i For k (k=0, 1, 2, 3, etc., up to 2n) polarization states, the following equation:

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[0037] Therefore, the parameter k τ i represents the transmission coefficient of surface i (1 or 2) for a ray of light initially of polarization x after k passes through the transparent substrate. The parameter int k ρ i represents the internal reflection coefficient of surface i (1 or 2) for a ray of light initially with polarization x after k passes through a transparent substrate. When the beam is repolarized with polarization x after 2n reflections,

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[0038] The parameters T1, T2, R1 and R2 are determined by the following formula:

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number

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[0039] Due to the small thickness of the lamina or stack of lamina, a glazing comprising the lamina or stack of lamina can be considered to have the same thickness as the same glazing lacking the thin film.

[0040] Based on at least one of these parameters T1, T2, R1, R2, which are known in the entire visible range, a person skilled in the art can determine for a viewing in transmission of face 1, for a viewing in transmission of face 2, for a viewing in reflection of face 1 or for a viewing in reflection of face 2, the color difference ΔE between the isotropic areas of the glazing substrate which do not induce an optical phase shift and the areas which induce an optical phase shift δ=π / n. s (θ,δ=π / n) can be calculated. ΔE s where the subscript S stands for T1, T2, R1 or R2 to indicate that a ΔE exists for each of these situations: transmission incident on surface 1, transmission incident on surface 2, reflection from surface 1, and reflection from surface 2. The above formulas giving T1, T2, R1 and R2 take into account multiple reflections within the glazing and multiple transmissions of partially reflected rays. The desired ΔE s(S=T1, T2, R1 or R2) is selected depending on the expected prevailing conditions of glazing observation.

[0041] In the context of the present invention, at least one of these parameters T1, T2, R1 or R2, which applies to the glazing proposed for investigation, is first calculated by a computer. Then,

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[0042] For n=2, the glazing has locally the effect of a quarter-wave plate. In the case of p-polarized light incidence, the light changes polarization for each pass through the glazing in the following path: p-polarized → circular → s-polarized → circular → p-polarized → circular etc.

[0043] For n=2, the glazing has locally the effect of a quarter-wave plate. In the case of p-polarized light incidence, the light changes polarization for each pass through the glazing in the following path: p-polarized → circular → s-polarized → circular → p-polarized → circular etc.

[0044] For n=2, the glazing has locally the effect of a quarter-wave plate. In the case of p-polarized light incidence, the light changes polarization for each pass through the glazing in the following path: p-polarized → circular → s-polarized → circular → p-polarized → circular etc.

[0045] The transmission and reflection coefficients for the intermediate (circular) polarization state are

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[0046] The transmission and reflection parameters of the substrate are then:

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number

number

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[0047] Function sin 2 is used as the function F1, where the optical phase shift is fixed at δ=π / 2 and sin 2 Since (π / 2)=1,

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[0048] Furthermore, the present invention relates to a process for producing a glazing, comprising, prior to the production of the glazing, carrying out a method according to the invention applied to said glazing. The method according to the invention is applied to two different glazing substrates V1 and V2, which are compared on the same metric, respectively, to obtain a σ V1 and σ V2 The two parameters σ V Derive σ V1 and σ V2A comparison of V1 and V2 makes it possible to determine which glazing should have a less obvious quench mark than the other. In particular, V1 may be the same as V2, except that it further comprises a coating system comprising a thin layer or a stack of thin layers on one or both of the two main faces of V1. It is thus possible to determine whether a coating system tends to hide or accentuate the quench mark before it is produced. Furthermore, the invention relates to a process for producing a glazing V1, comprising carrying out a method according to the invention applied to glazings V1 and V2, and then producing a coating system. In particular, the invention also relates to a process for producing a glazing, comprising an application step of applying a coating system to a glazing substrate, the application step comprising using a method according to the invention with the aim of selecting a coating system, and then a step of producing a coating system on the glazing substrate.

[0049] Furthermore, the invention relates to a computer program comprising program code instructions or instruction segments for performing at least one computer-implemented computational step of the method according to the invention. Furthermore, the invention relates to a computer-readable storage medium on which this computer program is stored. [Brief description of the drawings]

[0050] (No original text) EXAMPLES

[0051] Example 1 In particular, it is proposed to determine the effect of a thin layer stack including an 8 nm silver layer on the quench marks of a 10 nm thick Planiclear® (sold by Saint-Gobain Glass France) glass plate.

[0052] To do this, we investigate the phase shifts σ for various values ​​of the optical phase shift δ=π / n (n between 2 and 50), for an angle of incidence of 65°, for four spectra in the situations T1, T2, R1 and R2, and for coated (see Fig. 1) and uncoated glass plates (see Fig. 2). δ Determine the value of

[0053] In Figs. 1 and 2, the smaller the optical phase shift δ, the δ It can be seen that σ is more independent of the optical phase shift δ. For this reason, the relevant optical phase shift region in the context of the present invention is preferably close to 0 and starts at 0. In particular, σ as δ approaches 0 δ The limit of is a good value for characterizing the glazing.

[0054] In the case of an uncoated glass sheet (Figure 2), when the glazing is symmetric, surface 1 is the same as surface 2, and σ δ The values ​​of are the same, and σ δ The values ​​of are also the same, where these values ​​are the Fresnel coefficients.

[0055] Comparing Figures 1 and 2 shows that σ δ It shows that the value of σ is almost unaffected by the coating. In contrast, for the same optical phase shift, σ δ The value of is much smaller in the presence of the coating. The coating therefore has the effect of hiding the quench marks in situations R1 and R2 for a plain glazing substrate for an angle of incidence of 65°.

[0056] For angles of incidence varying from 45 to 85°, σ as δ approaches 0 δ We further calculated the limiting values ​​of . Figure 3 shows the results for the coated Planiclear and Figure 4 shows the results for the bare Planiclear.

[0057] The maximum sensitivity in external reflection (R2) for the coated glass is between 17.5 and 51°, whereas for the plain glass the maximum sensitivity in external reflection (R2) is between 41 and 62°. Overall the coating therefore has the effect of hiding the quench marks relative to the plain glazing substrate.

[0058] Example 2 The process was the same as for FIG. 1, except that the coating comprised a thin layer stack comprising two silver layers, 12 and 22 nm thick, respectively, deposited on face 1 of a 10 nm thick Planiclear glass plate. FIG. 5 shows the results. Here again, the smaller the optical phase shift δ, the greater the σ δ is less dependent on the optical phase shift δ. Moreover, it can be said that the coating has a hiding effect at 65° on the quench marks in situations R1 and R2 compared to the plain glazing substrate (compare with Fig. 2). For angles of incidence varying from 45 to 85°, σ as δ approaches 0 δ was further calculated, and the results are shown in Figure 6. Again, the maximum sensitivity is lower for the coated glass than for the bare glass (compare Figure 4), and it can be said that the coating attenuates the visibility of the quench marks. The present invention can be embodied in the following manner. (Appendix 1) A method for evaluating the susceptibility of a glazing to the formation of quench marks by the anisotropy of said glazing, said susceptibility being determined by a parameter σ V wherein the glazing comprises a face 1 and a face 2, both in contact with the external environment, and the quench marks are due to different optical phase shifts in different areas of the glazing, in transmission or reflection, and for viewing from either side of the glazing, a calculation step performed on a computer of at least one parameter of the transmission through surface 1 or surface 2, called T1 or T2, or at least one parameter of the reflection from surface 1 or surface 2, called R1 and R2, said calculation being performed on the one hand for areas of the glazing which do not induce an optical phase shift, and on the other hand for areas of the glazing which have a birefringence axis oriented at a given angle relative to the plane of incidence and which induce an optical phase shift δ in a light ray within a given optical phase shift, for a given polarization of the light ray and for a given angle of incidence of the light ray, a computer-implemented calculation step of calculating at least one parameter ΔE(δ) corresponding to a color difference between the areas of the glazing that do not induce an optical phase shift and the areas of the glazing that induce the optical phase shift δ, based on at least one of the parameters T1, T2, R1, R2, then σ by applying a function G that depends on the one or more calculated ΔE(δ) and, where appropriate, on the one or more corresponding δ. V Calculating A method comprising: (Appendix 2) The function G is a function of a σ determined for a given δ. δ or multiple σ determined for different δ δ is equal to any function F2 that depends only on δ 2. The method of claim 1, wherein F(δ) is equal to ΔE(δ) divided by a function F(δ) that depends only on the corresponding δ. (Appendix 3) The function F2 is δ 3. The method according to claim 2, wherein the polynomial function (Appendix 4) The function F1(δ) is, for each δ in question, (sin 2 δ)-1~(sin 2 4. The method of claim 2 or 3, wherein the method delivers a value contained in δ)+1. (Appendix 5) The function F1(δ) is, for each δ in question, (sin 2 δ)-0.5~(sin 2 5. The method of claim 4, wherein the method delivers a value included in δ)+0.5. (Appendix 6) The function F1(δ) is sin 2 6. The method of claim 5, wherein the δ is equal to δ. (Appendix 7) 7. The method according to any one of claims 1 to 6, wherein the one or more optical phase shifts δ are within a range of an optical phase shift from 0 to π / 2. (Appendix 8) 8. The method according to claim 7, wherein the one or more optical phase shifts δ are within a range of an optical phase shift from 0 to π / 15. (Appendix 9) 9. The method according to claim 8, wherein the one or more optical phase shifts δ are within a range of an optical phase shift from 0 to π / 30. (Appendix 10) σ V The one or more σ δ is a certain range of the optical phase shift δ, and when δ changes from the limit of ΔE / F1(δ) when δ approaches 0 infinitesimally to the maximum value of this range, σ δ The method according to any one of appendices 2 to 9, characterized in that is selected between a range in which varies by less than 0.5, preferably less than 0.2. (Appendix 11) σ V =F2(lim δ→0 11. The method according to any one of claims 2 to 10, wherein the ΔE / F1(δ) is satisfied. (Appendix 12) σ V =lim δ→0 The method described in Appendix 11, characterized in that ΔE / F1(δ) is used. (Appendix 13) σ V =lim δ→0 ΔE / sin 2 13. The method according to claim 12, wherein (δ) is (Appendix 14) The same metric is applied to two different glazing substrates V1 and V2 that are compared, respectively σ V1 and σ V2 The two parameters σ V The method according to any one of claims 1 to 13, further comprising deriving: (Appendix 15) 15. The method according to claim 14, wherein V1 is the same as V2, except that V1 further comprises a coating system comprising a thin layer or a stack of thin layers on one or both of the two main surfaces of V1. (Appendix 16) 14. A process for producing a glazing, comprising carrying out, prior to the production of said glazing, a method according to any one of claims 1 to 13 applied to said glazing. (Appendix 17) A process for producing said glazing V1, comprising carrying out the method according to claim 15 and then producing said coating system. (Appendix 18) A computer program comprising program code instructions or instruction segments for carrying out at least one computer-implemented computational step of the method according to any one of method appendices 1 to 15. (Appendix 19) 19. A computer-readable storage medium having stored thereon the computer program of claim 18.

Claims

1. A method for evaluating the susceptibility of a glazing to the formation of quench marks by the anisotropy of said glazing, said susceptibility being determined by a parameter σ V wherein the glazing comprises a surface 1 and a surface 2, both in contact with the external environment, and the quench marks are due to different optical phase shifts in different areas of the glazing, in transmission or reflection, and for viewing from either side of the glazing, a calculation step performed on a computer of at least one parameter of the transmission through surface 1 or surface 2, called T1 or T2, or at least one parameter of the reflection from surface 1 or surface 2, called R1 and R2, said calculation being performed on the one hand for areas of the glazing which do not induce an optical phase shift, and on the other hand for areas of the glazing which have a birefringence axis oriented at a given angle relative to the plane of incidence and which induce an optical phase shift δ in a light ray within a given optical phase shift, for a given polarization of the light ray and for a given angle of incidence of the light ray, T1 and T2 being the transmission coefficients of the light rays passing through the glazing after hitting surface 1 and surface 2 respectively and R1 and R2 being the reflection coefficients of the glazing for the light rays hitting surface 1 and surface 2 respectively, a computer-implemented calculation step of calculating at least one parameter ΔE(δ) corresponding to a color difference between the areas of the glazing that do not induce an optical phase shift and the areas of the glazing that induce the optical phase shift δ, based on at least one of the parameters T1, T2, R1, R2, then σ by applying a function G that depends on the one or more calculated ΔE(δ) and the one or more corresponding δ V To calculate Including, The function G is a function of a σ determined for a given δ. δ or multiple σ determined for different δ δ is an arbitrary function F2 that depends only on each σ δ is ΔE(δ) divided by a function F(δ) that depends only on the corresponding δ.

2. The function F2 is the one or more σ δ 2. The method of claim 1, wherein the eigenvalue is a polynomial function of

3. The function F1(δ) is, for each δ in question, (sin 2 δ) -1 ~ (sin 2 3. The method of claim 1, wherein the method returns a value contained in δ)+1.

4. The function F1(δ) is, for each δ in question, (sin 2 δ) -0.5~(sin 2 4. The method of claim 3, wherein the method returns a value included in the arithmetic mean of the arithmetic mean (δ) + 0.

5.

5. The function F1(δ) is sin 2 5. The method of claim 4, wherein the .lambda.

6. The method according to any one of claims 1 to 5, characterized in that all of said one or more optical phase shifts δ are comprised within the range of an optical phase shift between 0 and π / 2.

7. 7. The method of claim 6, wherein all of the one or more optical phase shifts δ are within the range of an optical phase shift from 0 to π / 15.

8. 8. The method of claim 7, wherein the one or more optical phase shifts δ are all within the range of an optical phase shift from 0 to π / 30.

9. σ V The one or more σ δ is a certain range of the optical phase shift δ, and when δ changes from the limit of ΔE / F1(δ) when δ approaches 0 infinitesimally to the maximum value of this range, σ δ 9. The method according to claim 1, wherein is selected between a range varying by less than 0.5, preferably by less than 0.

2.

10. σ V = F2 (lim δ→0 10. The method according to claim 1, wherein the ΔE / F1(δ) is the ΔE / F1(δ).

11. σ V =lim δ→0 The method according to any one of claims 1 to 9, characterized in that ΔE / F1(δ) is

12. σ V =lim δ→0 ΔE / sin 2 12. The method according to claim 11, characterized in that (δ).

13. The same metric is applied to two different glazing substrates V1 and V2 that are compared, respectively σ V1 and σ V2 The two parameters σ V The method according to any one of claims 1 to 12, characterized in that:

14. 14. The method according to claim 13, characterized in that V1 is the same as V2, except that V1 further comprises a coating system comprising a thin layer or a stack of thin layers on one or both of the two main faces of V1.

15. A process for producing a glazing, comprising carrying out a method according to any one of claims 1 to 12 applied to said glazing prior to the production of said glazing.

16. A process for producing said glazing V1, comprising carrying out the method according to claim 14 and then producing said coating system.

17. A computer program comprising program code instructions or instruction segments for carrying out at least one computer-implemented computational step of the method according to any one of claims 1 to 14.

18. A computer readable storage medium having stored thereon the computer program of claim 17.

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