Light guide plate and method for the production thereof

Patent metadata

Field	Value
Publication number	US-2016170128-A1
Application number	US-201414906961-A
Country	US
Kind code	A1
Filing date	Jul 3, 2014
Priority date	Jul 22, 2013
Publication date	Jun 16, 2016
Grant date	—

Abstract

The present invention relates to novel light guide plates composed of a reflector film, of a transparent sheet and of, situated between these, reactive hot-melts or colourless thermoplastics applied by structured printing. No fixed direct connection exists here between the reflector film and the transparent sheet.
Light guide plates, e.g. in backlight units (BLUs) or in light panels, have maximum uniformity of thickness and are composed of colourless transparent materials. Light is input here by way of example from LED or CCFL light sources by way of one or more edges of the light guide plate. On at least one surface of the light guide plate there is a structure which scatters the light. When a light beam is incident on the said structure, it is scattered at an angle smaller than the angle of total reflection, and is thus emitted from the plate. The light is emitted at both sides of the plate, and on one side there is therefore mostly a white reflector film which is not in optical contact with the plate. With this structure, the light is emitted only on one of the sides.

First claim

1 . A light guide plate comprising a a colorless transparent sheet and an opaque white or translucent white thermoplastic reflector film, wherein an optical connection between the colorless transparent sheet and the reflector film is provided by (i) a colorless thermoplastic applied by structured printing and having a glass transition temperature above 25° C. and below glass transition temperatures of a material of the colorless transparent sheet and of the thermoplastic of the reflector film, or by (ii) a reactive adhesive with an activation temperature between 25° C. and the glass transition temperature of the material of the colorless transparent sheet and of the thermoplastic of the reflector film, and wherein there is no direct optical contact between the colorless transparent sheet and the reflector film.

2 . The light guide plate of claim 1 , wherein the colorless transparent sheet comprises polycarbonate, a cycloolefin copolymer, PMMA, a copolymer of MMA and styrene, or of a blend comprising at least 50% by weight of PMMA.

3 . (canceled)

4 . The light guide plate of claim 1 , wherein a thickness of the light guide plate is from 1.5 to 4 mm.

5 . The light guide plate of claim 1 , wherein the reflector film comprises a film comprising opaque white PET or comprises a three-layer film with a semicrystalline middle layer comprising polypropylene comprising particles and with two exterior layers comprising a cycloolefin copolymer.

6 . The light guide plate of claim 1 , wherein a refractive index of the thermoplastic applied by printing is the same as or greater than a refractive index of the material of the colorless transparent sheet.

7 . The light guide plate of claim 1 , wherein the thermoplastic applied by printing further comprises scattering particles.

8 . The light guide plate of claim 1 , wherein a thickness of the reflector film is from 25 to 500 μm.

9 . The light guide plate of claim 1 , wherein the thermoplastic applied by printing has been applied by printing round, rectangular, strip-shaped, hexagonal or square structures, where the number and/or size of the structures increases with a distance from the edges through which the light is input.

10 . The light guide plate of claim 1 , wherein a thickness, between the colorless transparent sheet and the reflector film, of the thermoplastic applied by printing is from 0.5 to 200 μm.

11 . The light guide plate of claim 1 , wherein edges through which no light is input are equipped entirely or to some extent with a reflective layer.

12 . A process for the production of a light guide plate, comprising:
producing a sheet from a colorless transparent material by extrusion with a polishing stack, laminating in-line an opaque white or translucent white thermoplastic reflector film printed with a colorless thermoplastic to the sheet, and in a concluding in-line process, sawing the sheet into pieces, or cutting or winding the sheet onto a roll, where the wherein: a location of the print effect after the laminating is between the sheet and the reflector film, the sheet and reflector film are in optical contact, there is no direct optical contact between the colorless transparent sheet and the reflector film, and a glass transition temperature of the printed thermoplastic is above 25° C. and below glass transition temperatures of the colorless transparent material of the sheet and of the thermoplastic of the reflector film.

13 . The process of claim 12 , wherein, directly prior to the laminating, the surface of the sheet comprising PMMA is heated by a radiant heater, an IR source or a blower to a temperature above the glass transition temperature of the printed thermoplastic, and at least one roll is used to press the printed reflector film onto the surface of the sheet.

14 . The process of claim 12 , wherein at least one roll is used to laminate the printed reflector film onto the colorless transparent sheet directly after the polishing stack.

15 . An LCD display screen comprising the light guide plate of claim 1 .

16 . A sign or advertising panel comprising the light guide plate of claim 1 .

Assignees

• Groothues Herbert
• Schmidt Jann
• Karampougioukis Wangelis
• Häring Helmut
• Meumayer Stephan
• Schönig Berthold
• Evonik Röhn GMBH
• Evonik Roehm Gmbh

Inventors

• Groothues Herbert
• Schmidt Jann
• Karampougioukis Wangelis
• Neumayer Stephan
• Haering Helmut
• Schoenig Berthold

Classifications

• G02B6/0055 Primary

  Reflecting element, sheet or layer · CPC title

• G02B6/0043

  provided on the surface of the light guide · CPC title

• G02B6/0061

  to provide homogeneous light output intensity · CPC title

• G02B6/0065

  Manufacturing aspects; Material aspects · CPC title