Method for producing light guide bodies and use thereof in lighting unit

Patent metadata

Field	Value
Publication number	US-9442237-B2
Application number	US-201113993882-A
Country	US
Kind code	B2
Filing date	Nov 11, 2011
Priority date	Dec 13, 2010
Publication date	Sep 13, 2016
Grant date	Sep 13, 2016

Abstract

The present invention relates to a method for producing light guide bodies and to their use in lighting units, for example for liquid crystal displays or for monitors.
In particular, the present invention relates to a method for producing light guide bodies which have a thickness of at most 1 mm and contain at least 80 wt % of polymethyl methacrylate and no light-scattering constituents.

First claim

The invention claimed is:

1. A method for producing a methacrylate-based light guide body having a thickness of between 100 μm and 1 mm, the method comprising extruding a methacrylate-based material in an apparatus followed by smoothing, to produce a methacrylate-based light guide body,
wherein the apparatus comprises
an extruder,
an optional melt pump,
an optional melt filter,
an optional static mixing element,
a flat film nozzle,
a smoothing mechanism comprising smoothing rolls,
and optionally a winder;

the flat film nozzle comprises a nozzle lip comprising control elements for adjusting the nozzle lip width, said control elements having a mutual separation of from 11 to 15 mm, such that a nozzle body has an external geometry which is adapted to the shape of the smoothing rolls;
a distance from a melt exit edge to a smoothing gap is 80 mm or less; and
at least 95 wt % of the methacrylate-based light guide body consists of PMMA, and it does not contain any impact modifiers.

2. The method according to claim 1 , wherein the flat film nozzle is aligned with a laser in relation to the smoothing mechanism, and a parallel deviation of the nozzle from the smoothing rolls, measured at the two ends of an outer side of the nozzle, has a maximum deviation of 3 mm.

3. The method of claim 1 , wherein a difference between the thinnest and thickest points of the light guide body is at most 5 μm.

4. The method of claim 1 , wherein a thickness deviation in the light guide body is at most 4%.

5. The method of claim 1 , wherein the nozzle and the roll have chromium surfaces, and these chromium surfaces have a roughness Ra of less than 0.08 μm.

6. The method of claim 2 , wherein a difference between the thinnest and thickest points of the light guide body is at most 5 μm.

7. The method of claim 2 , wherein a thickness deviation in the light guide body is at most 4%.

8. The method of claim 1 , wherein a thickness deviation in the light guide body is at most 3%.

9. The method of claim 2 , wherein the nozzle and the roll have chromium surfaces, and these chromium surfaces have a roughness Ra of less than 0.08 μm.

10. The method of claim 1 , wherein the nozzle body has an external geometry which is a complementary shape to the shape of the smoothing rolls.

Assignees

• Parusel Markus
• Dickhaut Guenther
• Pfaff Thomas
• Haering Helmut
• Enders Michael
• Evonik Roehm Gmbh

Inventors

• Parusel Markus
• Dickhaut Guenther
• Pfaff Thomas
• Haering Helmut
• Enders Michael

Classifications

• B29C48/002

  combined with surface shaping · CPC title

• B29K2995/0073

  smooth · CPC title

• B29C48/0011

  combined with compression moulding · CPC title

• B29L2031/3475

  Displays, monitors, TV-sets, computer screens · CPC title

• B29C48/313

  by positioning the die lips · CPC title