RU2771627C2 - Transparent textured substrate, in particular, for greenhouse - Google Patents

Abstract

FIELD: greenhouse construction.

SUBSTANCE: group of inventions relates to weakly scattering textured substrate with high transparency, in particular, for horticultural greenhouses. Transparent substrate (1, 2) contains relief texture on at least one of its two main sides. This texture is made such that, when substrate is textured on one side (10), an average slope P_m, in degrees, for this textured side is less than 2°, when substrate is textured on its two sides (20, 21), the sum of two average slopes (P_m1, P_m2) of corresponding sides is less than 3°, preferably less than 2.5°.

EFFECT: use of the group of inventions will provide a horticultural greenhouse with transparent substrates having relief structural elements, an average slope of which provides increased TLH and very low turbidity, which is close to properties of float glass; in addition, structural elements are discrete in size and distributed along the entire surface, giving the surface a homogenous appearance.

10 cl, 3 dwg, 3 tbl

Description

The invention relates to a low scattering textured substrate with high transparency, in particular for horticultural greenhouses.

The invention is described in more detail in relation to a transparent substrate for horticultural greenhouses, without being, however, limited to this and can be used for all applications that require high hemispherical light transmittance (TLH), high light transmittance (TL) and low haze (H).

As far as greenhouse applications for horticulture are concerned, glazings with a smooth surface are mainly used because of their very high hemispherical light transmittance. Generally, a smooth surface is one for which the surface irregularities are smaller than the wavelength of the radiation incident on the surface, so that the radiation is not deflected by these surface irregularities. Thus, the incident radiation is transmitted specularly (or regularly) by the surface so that radiation incident on the glazing at a given angle of incidence would be transmitted by the glazing at a transmission angle depending on the angle of incidence. In theory, specular transmission entails that the incident beam is transmitted in the form of a single beam. In practice, the transmitted beam always contains a scattering component, but it is negligible during transmission, called specular.

Methods are known for producing glazing with a smooth surface on its two sides and high light transmittance from flat float glass, the float process consisting of pouring a glass ribbon from a furnace onto a bath of metal such as tin.

Smooth-surface glazings, due to their specular transmission, have the disadvantage of focusing the transmitted light rays at localized hot spots. As a result of these hot spots and/or non-uniform lighting in the greenhouse, certain types of crops may be affected.

In this context, it is known to use textured glazings in which the surface irregularities vary over a larger range than the wavelength of the radiation incident on the surface. Thus, the incident radiation is transmitted by being scattered by these surfaces. Transmission by a glazing is generally said to be diffuse when radiation incident on the glazing at a given angle of incidence is transmitted by the glazing in multiple directions. This diffuse transmission has a positive effect on the horticultural cultivation of the aforementioned sensitive crops. In this way, the scattering effect avoids hot spots on the plants and contributes to a better light penetration into all areas of the greenhouse. In other words, it allows you to get more uniform lighting.

The texture of such glasses is obtained by a rolling process of at least one of the metal cylinders having a textured surface that corresponds to the negative of the texture obtained on at least one side of the glass. Structural texture elements (patterns raised from the flat glass surface obtained at the output of manufacture) are, for example, bumps or prisms, such as conical prisms, or pyramids, which can be embedded in the base of the substrate in the form of a circle. Structural elements of relief (texture) are formed from holes/cavities/pores, made, as a rule, in the form of circles, formed on the surface and along the thickness of the substrate, and obtained by rolling with the help of rollers having shapes corresponding to the relief.

Throughout the text, the average slope (P _m ) of texture units was measured using an instrument commercially available from STIL called the Micromesure 2™. The period (Rsm) and height (Rz) of the structural elements were measured according to ISO 4287:1997 using an instrument called the Mitutoyo SJ-400™, and this instrument was equipped with a 1400 mm pen and used Gaussian cut-off (or basic wavelength) from 25 µm to 8 mm (quenching of waves with periods less than 25 µm and more than 8 mm).

It should be recalled that the period Rsm of the profile (i.e., according to the straight segment) of the surface is given by:

,

,

where Si is the distance between two elevated zero passes (median line), n+1 is the number of zero passes in the profile under consideration. This parameter Rsm is responsible for the distance between the peaks, i.e., per texture step, parallel to the common plane of the substrate. Rsm measurements are taken at a distance of at least 40 mm. For any point on the textured surface, Rsm around said point corresponds to the arithmetic mean Rsm of 10 star profiles from the point in question. To calculate Rsm around a single point, remove values greater than or equal to 40 mm. This avoids taking into account profiles along certain directrix lines of specific textures, such as a texture of parallel prisms, or straight lines between aligned pyramids (an undefined or uncalculated Rsm value). The average Rsm of the textured surface is also set by calculating the arithmetic mean Rsm around one point, and these points are selected on a square grid with a step of 5 cm.

It should be recalled that the profile height Rz, ie according to the straight segment of the surface, is the average of the five largest profile heights. Height is understood as the distance between the highest peak and the lowest depression along the length of the profile sample. Thus, the Rz parameter is responsible for the average maximum profile height.

The high transmittance required for greenhouses is such that it is called hemispherical transmittance (TLH, sometimes referred to as T _H EM), i.e., the average transmittance over several angles of incidence. For each angle of incidence, the intensity of all light passing through the glazing is measured, regardless of the exit angle. With regard to high scattering and even distribution of light, which are sometimes also required, they correspond to the blurring of the glazing, which is determined by the haze value, called H. Haze is the ratio between the diffuse transmittance and the total transmittance of the glazing. Throughout the description, TLH and haze ratio are measured according to methods detailed in "Proc 7th IS on light in Horticultural Systems, Eds: S. Hemming and E. Heuvelink, Acta Hort,956, ISHS 2012". This document refers to turbidity measured at 1.5°. However, in the field of transparent materials, haze is often measured at 2.5°. This standard has not yet been fully approved in the field of horticultural greenhouses, although turbidity at 1.5° is now widely used, in particular at Wagenigen University (WUR), renowned in the field of horticultural research.

Patent application WO2016/170261, filed in the name of the applicant company, describes textured glasses designed to achieve very high haze values in excess of 60% with limited loss of TLH. These glasses are specifically designed to be different from Groupe Saint-Gobain's Albarino-T™ brand glasses, which are considered too haze. It should be noted that Albarino-T™ brand glass is textured on its two opposite sides by hot rolling between two textured rolls. As indicated in the examples, these sides include texture elements with a slope P _m of 2° and 1.5°, respectively, and thus the sum of the two average slopes is 3.5°, for haze at light transmittance 20% at 1.5°.

The disadvantage of textured glasses, such as those described in WO2016/170261, is that they have a lower hemispherical light transmittance than the same non-textured glass, which is contrary to the basic function required for glass with increased transmittance. light needed for the gardening area. It should be noted that a gain or loss of 1% TLH will already be very significant.

Thus, from the viewpoint of the horticultural field, there is a need to provide a textured substrate that has a hemispherical light transmittance TLH close to that of float glass with smooth surfaces.

The present invention meets this requirement and relates, in at least one particular embodiment, to a transparent substrate containing an embossed texture on at least one of its two main sides, such that:

- when the substrate is textured on one side, the average slope _Pm in degrees for that textured side is less than 2°, and

- when the substrate is textured on its two sides, each of which has a respective average slope (P _ml , P _m2 ), the sum of the two average slopes of the respective sides is less than 3°, preferably less than 2.5°.

Throughout the text, the slope at a point on the sheet's surface defines the angle formed between the plane tangent at that point and the common plane of the substrate. The measurement of the slope at a point is made from the measurement of the change in height near that point and with respect to the general plane of the substrate. The average slope P _m of the surface is determined from measuring the slopes at points distributed over the surface according to a square grid with a period of 20 μm.

The substrate according to the invention has a very high hemispherical transmittance TLH and thus approaches the hemispherical transmittance of float glass with smooth surfaces while maintaining a textured surface. This hemispherical transmittance TLH increases with decreasing haze and vice versa. These two values are related to the surface roughness, more specifically to the average slope _Pm of the latter, and the invention is based on a new inventive concept of fixing an upper limit on the average slope _Pm , allowing satisfactory turbidity to be obtained while being minimal. In this context, it has been determined that a slope of less than 2° results in a surface having a haze of less than 10% at 1.5°, which is considered satisfactory. Such a surface has a fine and discrete texture with closely spaced structural elements.

The same reasoning applies for glasses having texture on their two opposite sides, based on the sum of their average slopes.

According to a particular embodiment, the substrate is characterized in that:

- when the substrate is textured on one side, the average slope _Pm in degrees for that textured side is less than 1.8°, preferably less than 1.7°, even more preferably less than 1.6°, even more preferably less than 1, 5°, even more preferably less than 1.4°, even more preferably less than 1.3°;

- when the substrate is textured on its two sides, each of which has a respective average slope (P _ml , P _m2 ), the sum of the two average slopes of the respective sides is less than 2.3°, preferably less than 2.1°, even more preferably less than 1.9°, even more preferably less than 1.7°, even more preferably less than 1.5°, even more preferably less than 1.3°.

Following the same logic of minimizing turbidity and maximizing hemispherical transmittance TLH, it is preferred that the maximum haze limit achievable be fixed at 5% at 1.5°, and preferably at lower haze values. The limit values of the mean slope P _m or the sum of the mean slopes (P _ml , P _m2 ) above allow these turbidity values to be obtained.

According to a specific embodiment, the refractive index of the material containing the texture is 1.4-1.65 at a wavelength of 587 nm.

According to a specific embodiment, the texture-containing material is made of mineral glass, and it is preferred that it includes an iron oxide with a total weight content (expressed in Fe ₂ 0 ₃ ) of at least 0.030%, in particular, at most at least 0.020%, and even 0.015%, and it is preferred that it be a soda-lime-silicate type glass with the following mass composition:

SiO2 _50-75 %

CaO 5-15%

MgO 0-10%

Na ₂ O 10-20%

K ₂ O 0-5%.

Specifications shown are for ultraclear glass type glass, specifically Diamant™ and Albarino™ glass matrices available from Saint-Gobain. The advantage of these glass substrates is that they have a light transmission coefficient of more than 90.5%, even more preferably more than 90.8%, even more preferably more than 91.0%, even more preferably more than 91.2%, even more preferably more than 91.4%. Thus, they differ from glasses called "clear", which are typically less than 90% light transmittance. Throughout text, light transmittance is measured in % according to NF EN410-2011 (illuminator D65; observer angle 2°) using a Lambda950™ spectrometer manufactured by Perkin Elmer.

According to a specific embodiment, the texture of said at least one substrate contains structural elements, the period of which is such that the average value of Rsm is less than 5 mm, preferably less than 2 mm, even more preferably less than 900 μm, even more preferably less than 850 µm, even more preferably less than 800 µm, even more preferably less than 750 µm, even more preferably less than 700 µm, even more preferably less than 650 µm, even more preferably less than 600 µm, even more preferably less than 550 µm.

The surface of the substrate, whether smooth or textured, may include deformations in the form of waviness having a very high period, on the order of tens of millimeters. When measuring roughness, this waviness is suppressed by applying Gaussian filters with a cutoff greater than the specified period value (in the case of an 8 mm sample). This waviness is usually hidden from the eye of the observer by the texture of the surface in question.

Surprisingly, it has been found that in the specific case of a haze of less than 10%, at 1.5°, optical defects associated with the presence of surface waviness can become visible to the eye of the observer, in particular when Rsm is more than 900 μm. This is because below a certain level of texturization, the haze for the transmitted beam no longer allows optical masking of the presence of this waviness.

Assuming Rsm values of less than 900 μm successfully suppresses these optical defects as these Rsm values are lowered. The threshold value of 900 µm was obtained empirically by measuring with a profilometer the values obtained on glass having this effect and rolled with two smooth rollers.

Nothing suggested the existence of this technological problem, as well as the technological solution proposed to eliminate it. In contrast, prior art studies, including patent application WO2016/170261, may prompt one skilled in the art to increase the value of the average Rsm to allow the actual printed texture to successfully approximate the texture of the roll, and therefore limit the adjustments needed for the structural elements of the roll. . Thus, the state of the art has introduced technological prerequisites that must be overcome in order to achieve the purpose of this particular embodiment of the invention, which constitutes an additional indicator of inventive step.

According to a particular embodiment, the substrate is characterized in that:

- when the substrate is textured on one side, the average slope _Pm in degrees for that textured side is greater than 0.3°, preferably greater than 0.4°, preferably greater than 0.5°, even more preferably greater than 0.7° , even more preferably more than 0.9°, even more preferably more than 1.0°, even more preferably more than 1.1°;

- when the substrate is textured on its two sides, each of which has a corresponding average slope (P _ml , P _m2 ), the sum of the two average slopes of the respective sides is more than 0.6°, preferably more than 0.8°, even more preferably more 1.0°, even more preferably more than 1.1°.

Always in the specific context of haze less than 10% at 1.5°, and in order to limit the optical defects associated with the presence of surface waviness, it has been confirmed that the assumption of values of the average slope P _m of more than 0.2° successfully allows to limit these optical defects, according to as these values of the average slope P _m increase.

According to a particular embodiment, the substrate comprises an anti-reflection coating on one or two of its major sides, preferably applied on said at least one textured side.

This anti-reflection effect can be obtained by depositing a single layer or multiple layers forming a stack, for example by liquid sol-gel deposition or using any other known adapted technology. The antireflection effect is chosen to be effective at wavelengths of 400-700 nm. The anti-reflection coating (anti-reflection layer or anti-reflection layer stack) typically has a thickness of about 10-500 nm. The anti-reflection layer is such that it matches the texture of the glass without changing it.

According to a particular embodiment, the texture is obtained by rolling the substrate structural material between two rollers, the first roller having a smooth surface and the second roller having a textured surface, or the two rollers having a textured surface.

For mineral glass, rolling is carried out in a hot state, in particular in the temperature range of 800 at 1300°C.

By means of the rolling process, which is a simple process requiring facilities that are easier to manufacture and less expensive than float processing, the textured glass according to the invention has characteristics very close to those of float glass, which is commonly used for horticultural greenhouses, thanks to the very high TLH.

In addition, the rolling method allows the use of special glass compositions that improve the optical properties of light transmission (at a higher TL value), even if these compositions with increased light transmission cannot be used in the float process, because they are incompatible with the tin bath used in the float process. .

Finally, although it is known that the rolling process for textureless flat glass (produced with smooth surface rollers) is not particularly appreciated because it tends to create localized defects on the surface, this drawback of the manufacturing method is not burdensome for the substrate of the invention. In fact, it turns out that the low texture printed on the substrate avoids possible localized surface defects.

According to a specific embodiment, the substrate is made of a completely monolithic material.

According to a specific embodiment, the texture may be made of a first material deposited on a substrate of a second material.

According to this particular embodiment, the texture is made of a first, relatively thin texture-containing material bonded to a second material that stiffens the entire substrate. It is advantageous if this first material has a minimum thickness allowing the creation of structural elements in the relief. It is preferred that the difference in refractive index of the two materials does not exceed 0.2, and preferably does not exceed 0.1. In this case, a plurality of materials are combined when the texture is obtained by embossing a sol-gel layer deposited on a transparent substrate, in particular, made of glass.

According to a specific embodiment, the substrate may also contain more than two materials.

According to a specific embodiment, the distribution of texture is made on all surfaces of the substrate.

The invention also relates to a horticultural greenhouse provided with such a substrate.

The invention also relates to a method for manufacturing such a substrate by rolling between two rollers, i.e., between a smooth surface roller and a textured structural element roller, or between two textured structural element rollers, in particular, one or more textured rollers have printing Structural elements having an average slope exceeding, preferably exceeding by 1°, the average slope of their associated structural elements obtained on the substrate.

The texture of the rolled substrate depends on the shape of the printing structural elements of the surface of the roller and their roughness, as well as on the parameters associated with the method, such as the height of the roller, the pressure exerted by the roller, the feed rate of the rolled material.

In order to obtain said average inclinations of the substrate according to the invention, and depending on the adjustment parameters of the method, one or more textured rollers have, in particular, printing structural elements having an average inclination greater, preferably by 1°, than the average inclination of the structural elements associated with them. obtained on the substrate.

Thus, the invention proposes the manufacture of textured horticultural glass by rolling, with special texturing, instead of the float glass commonly used in this horticultural glass market. The rolling method is economical, and the glass with the texturing characteristics of the invention advantageously has properties equivalent to those of float glass.

According to a specific embodiment, one or more textured structured rolls are produced using electrical discharge machining.

Electrical discharge machining, also called EDM (electrical discharge machining), is a machining method that consists in removing material from a part using electrical discharges. This method is particularly adapted to the machining of the special shapes that make up the texture of the rolls, in particular due to its very high precision (tolerance +/- 5 µm) and the quality of the surface condition of the roll to be machined.

In particular, this machining method is more suitable for roller texturing than other known laser or pressure roller machining techniques that one skilled in the art would suggest.

The present invention will now be described by way of examples, which are illustrative only and do not limit the scope of the invention in any way, and based on the accompanying illustrations, in which:

- Figure 1 is a schematic section according to the first example of a textured substrate according to the invention, containing one textured side obtained by rolling;

- Figure 2 is a top view photograph of an example of Figure 1;

- Figure 3 is a schematic sectional view of a second example of a textured substrate according to the invention, containing two opposite textured sides.

Textures and thicknesses in Figures 1 and 3 are not to scale.

Textured substrates 1 and 3, illustrated in the respective Figures 1 and 3 in section along their cut, are two corresponding embodiments according to the invention, where the first example of the substrate has only one main textured side, while the second example shows two main opposite textured sides .

The textured substrates of the invention are such that:

- when the substrate is textured on one side, the average slope _Pm in degrees for that textured side is less than 2°, and

- when the substrate is textured on its two sides, each of which has a respective average slope P _ml , P _m2 , the sum of the two average slopes of the respective sides is less than 3°, preferably less than 2.5°.

According to the embodiments illustrated in these Figures, textured side structural elements are distributed over the entire surface of the substrate.

Textured substrate 1 (Example 1) was made of 3-5 mm thick mineral soda-lime-silicate glass obtained by hot rolling between two rollers, of which the larger roller had a smooth surface while the smaller roller had a textured printing surface. The substrate 1 has a first flat side 10 and an opposite second textured side 11. The features in the pattern of the textured side 11 correspond to the features in the negative of the textured surface (print features) of the roller.

The structural elements of the textured side in example 1, schematically shown in Figure 1 and illustrated in Figure 2, are formed from a plurality of alternations of bumps and troughs, obtained with a roller containing raised structural elements/shapes, in this case on a circular base.

The textured print surface roughness of Example 1 has the following characteristics at a given length profile, where measured according to ISO 4287:1997:

- arithmetic mean profile roughness: Ra=2.55 µm;

- maximum profile height: Rz=19.85 µm;

- width or average period of structural elements on the profile relief (already specified above):

- average Rsm=191 microns;

- density of peaks per centimeter of profile length: RPc=52.35/cm.

The substrate 1 obtained according to this example 1 has such an embossed texture that the average slope P _m is 1°. The texture is such that the period according to the average Rsm is 0.53 mm and the height Rz is 5.6 µm.

Substrate 2 according to the invention (Example 2) is made of mineral soda-lime-silicate glass obtained by hot rolling between two rollers with a textured printing surface, the substrate having two opposite textured sides 20 and 21.

The rollers used for example 2 each have their own textured printing surface, and its roughness is the roughness specified for the roller of example 1.

The obtained substrate 2 has such a relief texture that the average slope P _ml of the first surface (the surface obtained by the smaller roller) is 1°, and the average slope P _m2 of the second surface (the surface obtained by the large roller) is 1°, and the sum of the average slopes is 2 (P _ml +P _m2 ).

In Table 1 below, for two examples 1 and 2 of the invention and comparative examples 3-5 (which do not correspond to the invention), the values of the height Rz, the period according to the average Rsm of the structural element of the textured substrate, the average slope P _m (substrate textured on one side) were presented or the sum of the average slopes (substrate textured on two sides), TLH of the substrate, TLH loss (ATLH) and haze at 1.5°.

The TLH loss is equal to the TLH difference between the TLH of the measured substrate and the reference TLH of the flat float glass. The flat float glass taken as the reference is a glass called DIAMANT™ manufactured by Saint Gobain which has an elevated TLH of 84% and a haze of 0.

Example 3, which is a comparative example, is Albarino-T™ industrial glass. This glass of Example 3 has two opposite sides textured by a roller with a roughness and with rolling process parameters resulting in a substrate exhibiting respectively a first average slope P _ml of 2° and a second average slope P _m2 of 1.5 °, which gives the sum of these average slopes equal to 3.5°.

Example 4, which is a comparative example, is a substrate having one textured side, the texture of which is such that it matches the texture obtained for one side of the Albarino-T™ glass in comparative example 3. This substrate exhibits an average slope of 2° .

Example 5, which is a comparative example, is a substrate, one of the textured sides of which was obtained by the textured surface print roller of Examples 1 and 2, and of which the opposite side of the textured side was obtained by a roller identical to the roller providing one of the textured of the Albarino-T™ glass surfaces of Example 3. The substrate of Example 5 exhibits a first average slope P _ml of 1° and a second average slope P _m2 of 2°, resulting in a sum of average slopes of 3°.

Table 1

Example No. Height Rz (µm) Average Rsm (mm) P _m (*) or sum of P _m (*) TLH (%) ΔTLH (%) Turbidity (% at 1.5°) Float glass Diamant ^TM - - 0° 84 - - Example 1 5.6 0.53 P _m =1° 83.7 0.3 5 Example 2 5.6 0.53 Sum P _m =2° 83.5 0.5 eight Example 3 - Albarino-T ^™ 25 on one side / 13 on the other side 0.8 on one side / 1.1 on the other side Sum P _m =3.5° 83 one nineteen Example 4 25 0.8 P _m =2° 83.5 0.5 eleven Example 5 5.6 on one side / 13 on the other side 0.53 on one side / 0.8 on the other side Sum P _m =3° 83.2 0.8 fourteen

It should be noted that example 1 according to the invention, with an average slope of less than 2°, in particular equal to 1°, is fully suitable for obtaining the desired result, with high TLH, with a TLH loss of less than 1% (in particular 0.3%) and turbidity of 5%, i.e. less than 10%.

Similarly, example 2 of the invention, with a sum of mean slopes of less than 3°, in this case equal to 2°, met the desired results with a loss of TLH of 0.5% (i.e., less than 1%) and a haze of 8% (i.e. less than 10%).

On the contrary, Comparative Example 3 shows that when the average slopes on each textured side are 2° and 1.5°, respectively, the sum of the average slopes is not less than 3°, and the result is not achieved, and thus the haze of the substrate becomes too high as it is 19%.

Similarly, Comparative Example 4, with a single textured side that has an average slope of 2°, of course has less than 1% TLH loss, but already has significant haze of over 10%. This pad is not suitable.

Similarly, Comparative Example 5 shows that if there are two textured sides with average slopes, albeit weak, of 1° and 2°, respectively, but the sum of which is not less than 3°, the result is not achieved. The loss of TLH is certainly 0.8%, but the turbidity is too significant and amounts to 14% (i.e. more than 10%).

Table 2 provides an estimate of the haze value at light transmission at 1.5° for an Albarino ultra-clear matrix containing a single textured surface, depending on its average slope P _m .

This estimate is based mainly on the approximation made of determining the slope, depending on the roughness parameters according to the following equation:

As indicated at the beginning of the text, the Rz parameter corresponds to the maximum profile height at the score length I, while the Rsm parameter corresponds to the average profile period at the score length I. Assuming that the structure is relatively uniform, one can make an approximation that Rz is equal to the average height at the score length. It is then possible to relate the average slope Pm to the _Rsm and Rz values using the following equation, which brings us to the previous expression for the slope versus roughness parameters.

The estimate of the haze value is more based on a second hypothesis, made from the available slope distribution, when considering the overall desired average slope P _m (target value). To do this, first, from the measurements of the available samples, a measured sample having an average slope closer to this target value is selected. Then, a linear expansion factor is applied to the slope distribution function of this sample to model a new slope distribution having a target mean slope value. Finally, the turbidity associated with this simulated slope distribution is calculated.

table 2

Example No. Rsm/Rz P _m (*) Turbidity (% at 1.5°) one 572 0.2 0 2 381 0.3 0 3 229 0.5 0.5 4 163 0.7 0.5 5 127 0.9 0.5 6 114 one one 7 104 1.1 one eight 95 1.2 one nine 88 1.3 1.5 ten 81 1.4 1.5 eleven 76 1.5 2 12 71 1.6 2.7 thirteen 67 1.7 3.2 fourteen 63 1.8 4.5

The results of Table 2 show that for each of Examples No. 1-14, for which the slope value is less than 1.8°, a turbidity of less than 5% is obtained, with the turbidity value increasing with the average slope P _m .

Table 3 provides an estimate of the haze value in transmission at 1.5° for an Albarino ultraclear matrix containing two opposite textured surfaces, depending on the sum of the average slopes (P _ml , P _m2 ) of each of these sides. This assessment was made on the basis of a hypothesis, which led to the results presented in Table 2.

Table 3

Example No. P _m1 (*) P _m2 (*) Sum of P _m1 (*) and P _m2 (*) Rsm/Rz Turbidity (% at 1.5°) one 0.27 0.27 0.54 212 0 2 0.63 0.63 1.26 90 one 3 one 0.88 1.88 60 2.7 4 0.76 0.76 1.52 75 2.8 5 one one 2 57 3.2 6 1.2 0.88 2.08 55 3.5 7 1.2 0.7 1.9 60 3.8 eight 1.5 0.88 2.38 48 5 nine 1.2 1.2 2.4 47 6.5 ten 1.4 one 2.4 47 6 eleven 1.5 one 2.5 45 6 12 1.8 1.5 3.3 34 15.7 thirteen 1.8 1.8 3.6 31 19.4

The results of Table 3 show that for each of Examples No. 1-7, for which the sum of the slopes is less than 2.3°, a haze of less than 5% at 1.5° is obtained. Examples No. 8-11, for which the sum of the slopes is less than 3°, allow for them to obtain a turbidity of less than 10%. Finally, examples No. 12 and 13 show a turbidity of more than 10%, which, therefore, does not meet the general technical objective of the invention.

Finally, by using a rolling process with suitable roughness of the printing surfaces of the rollers, in combination with the parameters of the method implementation, the invention provides transparent substrates that have structural features of the relief, the average slope of which provides increased TLH and very low haze, which approximates the properties of float glass. , yet they are aesthetically pleasing, and the structural elements are discrete in size and distributed over the entire surface, giving the surface a uniform appearance.

According to a specific embodiment, the invention also relates to a horticultural greenhouse provided with at least one substrate such as described above.

Claims (19)

1. A substrate for a horticultural greenhouse, comprising an embossed texture on at least one of its two main sides, such that: - when the substrate is textured on one side, the average slope _Pm in degrees for that textured side is less than 2°, and - when the substrate is textured on its two sides, each of which has a corresponding average slope (P _ml , P _m2 ), the sum of the two average slopes of the respective sides is less than 3°, preferably less than 2.5°, wherein the texture-containing material is made of mineral glass and preferably includes iron oxide with a total weight content (expressed as Fe ₂ O ₃ ) of at least 0.030%, in particular at most 0.020% and 0.015% , wherein the glass is preferably a soda-lime-silicate type glass with the following mass composition: _SiO2 50-75% CaO 5-15% MgO 0-10% _Na2O 10-20% _{Al2O3 _} 0-5% _K2O 0-5%, and the texture is obtained by rolling the substrate material between two rollers, the first roller having a smooth surface and the second roller having a textured surface, or the two rollers having a textured surface. 2. Substrate according to claim 1, characterized in that: - when the substrate is textured on one side, the average slope _Pm in degrees for that textured side is less than 1.8°, preferably less than 1.7°, even more preferably less than 1.6°, even more preferably less than 1.5°, even more preferably less than 1.4°, even more preferably less than 1.3°, - when the substrate is textured on its two sides, each of which has a corresponding average slope (P _ml , P _m2 ), the sum of the two average slopes of the respective sides is less than 2.3°, preferably less than 2.1°, even more preferably less than 1, 9°, even more preferably less than 1.7°, even more preferably less than 1.5°, even more preferably less than 1.3°. 3. The substrate according to one of paragraphs. 1 and 2, characterized in that the refractive index of the material containing the texture is 1.4-1.65 at a wavelength of 587 nm. 4. The substrate according to one of paragraphs. 1-3, characterized in that the texture of said at least one substrate contains structural elements, the period of which is such that the average Rsm is less than 5 mm, preferably less than 2 mm, even more preferably less than 900 μm, even more preferably less than 850 μm, even more preferably less than 800 µm, even more preferably less than 750 µm, even more preferably less than 700 µm, even more preferably less than 650 µm, even more preferably less than 600 µm, even more preferably less than 550 µm. 5. The substrate according to one of paragraphs. 1-4, characterized in that: - when the substrate is textured on one side, the average slope P _m in degrees for this textured side is more than 0.3°, preferably more than 0.4°, preferably more than 0.5°, even more preferably more than 0.7°, even more preferably more than 0.9°, even more preferably more than 1.0°, even more preferably more than 1.1° but less than 2°, - when the substrate is textured on its two sides, each of which has a corresponding average slope (P _ml , P _m2 ), the sum of the two average slopes of the respective sides is more than 0.6°, preferably more than 0.8°, even more preferably more than 1, 0°, even more preferably more than 1.1° but less than 2.5°. 6. The substrate according to one of paragraphs. 1-5, characterized in that it includes an anti-reflection coating on one or two of its main sides, preferably deposited on said at least one textured side. 7. The substrate according to one of paragraphs. 1-6, characterized in that the texture can be made in the first material applied to the substrate of the second material. 8. Horticultural greenhouse, equipped with at least one substrate according to any one of the previous paragraphs. 1-7. 9. A method of manufacturing a substrate according to any one of paragraphs. 1-7 by rolling between two rollers, between a smooth surface roller and a textured textured roller, or between two textured textured rollers, in particular, one or more textured rollers have printing structural elements having an average slope exceeding, preferably, per 1° is the average slope of the associated structural elements obtained on the substrate. 10. A method for manufacturing a substrate according to claim 9, characterized in that one or more textured rollers with structural elements are obtained using electrical discharge machining.

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