SHEET MATERIAL WITH WINDOW, METHOD OF ITS MANUFACTURING AND PROTECTED DOCUMENT WITH SUCH MATERIAL Russian patent published in 2011 - IPC D21H27/30 D21H21/40 D21H21/42 D21F11/08 B42D15/10 

FIELD: textile, paper.

SUBSTANCE: sheet material, a protective sheet and a protected document include at least two layers applied one onto the other. Besides, the first layer contains at least one lengthy section of zero thickness, and the second layer contains at least one groove, at the same time the specified at least one groove in the second layer is arranged opposite to the specified at least one section of zero thickness of the first layer, thus forming a window. Methods relate to manufacturing of sheet material and making a protected sheet. Method to make a sheet material includes the following stages. Making the first layer of paper specified above by filtration of cellulose fibre suspension on the metal cloth of the first cylindrical shape or a forming device. Making the second layer of paper on the metal cloth of the second cylindrical shape with formation of at least one groove in the second layer. Then two layers are combined and dried. Method to make a protective sheet repeats the above-specified method with inclusion of the stage, where at least partially transparent element is fixed in the longitudinal section of zero thickness of the first layer of the sheet material.

EFFECT: expanded assortment of protected materials, improvement of their protective properties with provision of tactile effect.

43 cl, 7 dwg