The present invention relates to materials that provide a different degree of screening in the two directions of sight according to the intensity of the light that illuminates the two sides thereof, and in particular to a material in which said effect is achieved through a calibrated opacification of a portion of the surface of at least one of the sides, hi the following, specific reference will be made to a glass pane to be used in a window, but it is clear that what will be said also applies to similar transparent materials (e.g. Plexiglas or other type of plastic materials) and to different applications in the fields of building and furnishing, such as doors, wardrobe doors, dividing walls, shower booths, lamps, etc. As a consequence, the term "pane" as used herein is not meant to be limited to a flat rectangular element, but also includes elements with curved surface and with any contour.

It is known that there are glass panes treated to act as a one-way mirror, i.e. the more illuminated side acts as a mirror whereas the less illuminated side allows to see through, said effect being reversed when the light intensity on the two sides is swapped. A typical example are the windows of the buildings that in daylight reflect the image of the surrounding environment yet allowing the people inside to look out, whereas at dark it is possible from outside to see the internal rooms that are lit.

However, such a type of known panes allows only this mirror effect and nothing else, whereby it limits the choice of the user of said material. Moreover, since the effect is achieved by applying a thin coating layer on the glass, in case of deterioration or damage of said coating also the mirror effect is affected.

Therefore the object of the present invention is to provide a material which is free from the above-mentioned drawbacks. This object is achieved by means of a transparent material worked with a calibrated opacification of a portion of the surface of at least one of the sides according to the parameters and the ranges

disclosed in claim 1. Other advantageous features of the present material are specified in the dependent claims.

A first great advantage of this material is that of providing a differential screening in the two directions of sight without this implying a mirror effect, thus allowing a wider choice to the user.

A second significant advantage is that the screening effect can be achieved with a great freedom in the selection of the values of the working parameters, therefore with a wide range of aesthetic result of the material.

Still another advantage of the present material, in the embodiments with opacification through chemical or mechanical treatment, is the greater resistance to deterioration, that does not affect the screening effect.

Further advantages and characteristics of the material according to the present invention will be clear to those skilled in the art from the following detailed description of some embodiments thereof, with reference to the annexed drawings wherein:

Fig.l is a diagrammatic front view of a pane of material worked with a regular opacification pattern; and

Figs.2, 3 and 4 are views similar to the preceding one of other panes of material, with decreasing percentage of opacified surface and different working patterns.

With reference to fig.l, there is illustrated by way of example a square pane Pl that has a side partially opacified according to a regular pattern that leaves transparent round regions R arranged in staggered horizontal rows. These regions R have a diameter of 1,2 mm (i.e. an area of about 1,13 mm ² ), whereby the non- worked surface is equal to 14,1% of the area of pane Pl, that is to say that 85,9% of the pane is opacified.

It should be noted that in the drawing the opacified surface is depicted in black for the sake of clarity, so as to obtain a clear contrast between the worked and non- worked regions, but said surface will actually be semi-transparent. More specifically, the light transmission factor of the opacified region will be between 75% and 90%, and this partial blocking of the light can be obtained

through a chemical treatment (e.g. satin-etching), or a mechanical treatment (e.g. sandblasting) or by applying a suitable paint coating (e.g. silk screen printing). It should be noted that the light transmission factor is calculated according to the procedures described in the specification EN 410: 1998 "Glass in building - Determination of luminous and solar characteristics of glazing".

As illustrated in fig.2, the working of the pane does not necessarily follow a regular pattern and/or provide transparent regions of geometric shape since in the case of pane P2 there are provided "flower-shaped" transparent regions F arranged in an irregular pattern. These regions F have an area of about 2,5 mm ² , whereby the non-worked surface is equal to about 32,5% of the area of pane P2, that is to say that 67,5% of the pane is opacified.

Finally, figures 3 and 4 show other two embodiments of panes with a grid working with transparent regions of different shape and size. In particular, pane P3 has square transparent regions S arranged in horizontal aligned rows, having an area of 4 mm ² whereby the non- worked surface is equal to 36% of the area of pane P3, that is to say that 64% of the pane is opacified. Similarly, pane P4 has round transparent regions R' arranged in horizontal aligned rows, having a diameter of 2,5 mm (i.e. an area of about 4,91 mm ² ), whereby the non- worked surface is equal to about 44,2% of the area of pane P4, that is to say that 55,8% of the pane is opacified.

In practice, the above-described differential screening effect is achieved by working the transparent material of the pane according to the following parameters: a) total area of the transparent regions: from 10% to 45% of the pane area; b) area of the single transparent region: from 0,5 mm ² to 5 mm ² ; c) light transmission factor of the opacified region: from 75% to 90%.

In this way the whole pane P1-P4 has a global light transmission factor, always calculated according to the above-mentioned specification, between 80% and

95%. It is clear that the above-described and illustrated embodiments of the material according to the invention are just examples susceptible of various

modifications. In particular, the alternation between transparent regions and opacified regions can be obtained with any shape and arrangement of said regions as long as you remain within the above-mentioned ranges of the working parameters. Moreover, the working can be performed, if desired, on both sides in order to achieve a still greater effect.