Methods for thickness control of a substrate

Abstract

Method for thickness control of a glass ribbon, comprising at least the following steps: a) Providing a glass ribbon by drawing it from the melt or redrawing a preform at a withdrawal speed v GB and a mean thickness D in the net area b) Specifying a target thickness of the glass strip, c) Determining the thickness of the glass ribbon across its entire net width, d) Determine at least one deviation of the thickness of the glass ribbon from the specified target thickness, e) Determining the area of ​​thickness variation on the glass strip, f) Heating the area of ​​at least one thickness deviation on the glass ribbon by means of a laser, wherein the laser beam acts on and heats the area of ​​the thickness deviation, wherein the heating causes the area to assume the predetermined thickness, and wherein the heating further comprises controlling at least the power of the laser beam, the irradiation time of the laser beam or the wavelength of the laser as a function of the thickness of the glass ribbon determined in step c), wherein the laser is equipped with a scan head such that the entire net width of the glass strip can be scanned, and between the net width of the glass strip B, the peeling speed of the glass strip v GB , the beam diameter D of the laser beam and the scanning speed of the laser v Las and a correction factor k, the following relationship exists: 2 ⋅ k ⋅ v GB ⋅ B < D ⋅ v Las, where the correction factor k is at least equal to 1, preferably greater than 1.

Claims

[1] Method for checking the thickness of a glass ribbon, comprising at least the following steps: a) Providing a glass ribbon by drawing it from the melt or redrawing a preform at a drawing speed v GB and an average thickness D in the net area, b) Specifying a target thickness of the glass ribbon, c) Determining the thickness of the glass ribbon over its entire net width, d) Determining at least one deviation of the thickness of the glass ribbon from the specified target thickness, e) Determining the range of thickness deviation on the glass ribbon, f) heating the region of the at least one thickness deviation on the glass ribbon by means of a laser, wherein the laser beam acts on the region of the thickness deviation and heats it, wherein the heating results in the region assuming the predetermined thickness, and wherein the heating further comprises controlling at least the power of the laser beam, the irradiation time of the laser beam or the wavelength of the laser depending on the thickness of the glass ribbon determined in step c), wherein the laser is equipped with a scanning head such that the entire net width of the glass ribbon can be scanned, and between the net width of the glass ribbon B, the pulling speed of the glass ribbon v GB , the beam diameter D of the laser beam and the scanning speed of the laser v Las and a correction factor k, the following relationship exists: 2⋅k⋅vGB⋅B <D⋅vLas, wherein the correction factor k is at least equal to 1, preferably greater than 1. [2] Method according to claim 1, wherein the correction factor k is greater than 10 or at least equal to 10. [3] Method according to one of claims 1 or 2, wherein the region of the at least one thickness deviation before heating has a viscosity in the range between 10 4 and 10 9 dPas, preferably between 10 4 and 10 8 dPas, where areas with excessive thickness are exposed to higher laser power than areas with appropriate or insufficient thickness [4] Method according to one of claims 1 to 3, wherein the optical lever or the length of the light path between the glass ribbon and the scanner mirror is between at least 1.8 m and at most 5.0 m. [5] Method according to one of claims 1 to 4, wherein the laser power is at most 3000 W, preferably at most 2000 W and particularly preferably at most 1500 W. [6] Method according to one of claims 1 to 5, wherein the laser radiation acts on the deformation zone of the glass ribbon. [7] Method according to one of claims 1 to 6, wherein the drawing out takes place under the weight of the glass ribbon. [8] Method according to one of claims 1 to 7, wherein the laser is designed as a CO2 laser. [9] Method according to one of claims 1 to 8, wherein the thickness of the glass ribbon is determined by means of interference measurement, chromatic confocal measurement, white light topography and / or white light interferometry. [10] Method according to one of claims 1 to 9, wherein the laser beam is directed by means of a galvanometer scanner and / or a polygon mirror wheel. [11] Method for controlling the thickness between a first and a second surface of at least one selected area of ​​a glass or plastic substrate without undulations of greater than 5 mm wavelength, preferably without undulations of greater than 1 mm wavelength, comprising: a) Providing a molten glass or plastic, b) forming the molten glass or plastic into a ribbon, the forming not including the application of tension to the edges of the ribbon, c) monitoring a thickness of the strip, d) Detecting at least one thickness deviation in the strip, e) selecting at least one region of the substrate in the viscous state, wherein the at least one region corresponds to the region of the detected thickness deviation, and f) heating the at least one selected region of the strip in the viscous state with a laser beam directed to act on the selected region, wherein the heating results in the at least one selected region of the strip assuming a predetermined thickness, and wherein the heating further comprises at least controlling the power, the dwell time or the wavelength of the laser beam acting on the selected region as a function of the monitored thickness, wherein the laser is equipped with a scanning head such that the entire net width of the strip can be scanned, and further between the pulling speed of the strip v B , the net width B of the strip, the beam diameter D of the laser beam, the scanning speed of the laser v Las and a correction factor k, the following relationship exists: 2⋅k⋅vB⋅B <D⋅vLas, wherein the correction factor k is at least equal to 1, preferably greater than 1. [12] Method for controlling the thickness between a first and a second surface of at least one selected area of ​​a glass or plastic substrate without undulations of greater than 5 mm wavelength, preferably without undulations of greater than 1 mm wavelength, comprising: a) Providing a molten glass or plastic, b) forming the molten glass or plastic into a ribbon, the forming comprising applying a tension to the edges of the ribbon, c) monitoring a thickness of the strip, d) Detecting at least one thickness deviation in the strip, e) selecting at least one region of the substrate in the liquid state, wherein the liquid state has a viscosity of less than 10 9dPas, and wherein the at least one area corresponds to the area of ​​the detected thickness deviation, and f) heating the at least one selected region of the strip in the liquid state with a laser beam directed to act on the selected region, wherein the heating results in the at least one selected region of the strip assuming a predetermined thickness, and wherein the heating further comprises at least controlling the power, the dwell time or the wavelength of the laser beam acting on the selected region as a function of the monitored thickness, wherein the laser is equipped with a scanning head such that the entire net width of the strip can be scanned, and furthermore between the pulling speed of the strip v B , the net width B of the strip, the beam diameter D of the laser beam, the scanning speed of the laser v Lasand a correction factor k, the following relationship exists: 2⋅k⋅vB⋅B <d⋅vlas,wherein the correction factor k is at least equal to 1, preferably greater than 1. [13] Method according to one of claims 11 or 12, wherein the correction factor k is greater than 10 or at least equal to 10. [14] Method according to one of claims 11 to 13, wherein the optical distance or the length of the light path between the belt and the scanner mirror is between at least 1.8 m and at most 5.0 m. [15] Method according to one of claims 11 to 14, wherein the scanning head has a galvanometer drive and / or a polygon mirror wheel. [16] Method according to one of claims 11 to 15, wherein the laser power is at most 3000 W, preferably at most 2000 W and particularly preferably at most 1500 W. [17] Method according to one of claims 11 to 16, wherein the pulling of the band takes place under its own weight. [18] Method according to one of claims 11 to 17, wherein the laser is designed as a CO2 laser. [19] Method according to one of claims 11 to 18, wherein the monitoring of the strip thickness is carried out by means of interference measurement, chromatic confocal measurement, white light topography and / or white light interferometry. [20] A method according to any one of claims 11 to 19, wherein heating comprises directing the laser beam from a device for generating the laser beam to a reflective surface and reflecting the laser beam therefrom to the at least one selected region. [21] A method according to any one of claims 11 to 20, wherein the laser beam is successively directed onto a plurality of selected regions of the strip. [22] The method of claim 21, wherein the plurality of selected regions extend across the entire net width of the strip. [23] Method according to one of claims 21 or 22, wherein for each of the selected areas at least the power, the dwell time and / or the wavelength of the laser beam are specifically controlled and regulated. [24] Method according to one of claims 11 to 23, wherein absorption of the laser beam occurs with at least 20% of its power in the band. [25] A method according to any one of claims 11 to 24, wherein the molten glass or the molten plastic is introduced into a preform of glass or plastic in a melting process followed by shaping or by redrawing while heating. [26] A method according to claim 25, wherein the hot forming is carried out in a float process, a drawing process, for example a down-draw process, or an overflow fusion process. [27] Flat glass with a thickness of 300 µm or less, a thickness variation of not more than 25 µm based on the substrate sizes in the range of more than 100 mm in diameter, in particular with a lateral dimension of 100 mm - 100 mm or more, and furthermore without waviness of more than 5 mm wavelength, wherein the glass is an alkali silicate glass, an alkali-alkaline earth silicate glass, a soda-lime glass, a mixed alkali-lime silicate glass, a borosilicate glass, a phosphate silicate glass, a borophosphate silicate glass, an aluminum silicate glass, an alkali-aluminum silicate glass, an alkali-alkaline earth aluminum silicate glass, a boroaluminum silicate glass or a borophosphate aluminum silicate glass.

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