Light guide plate and method for fabricating the same

Patent metadata

Field	Value
Publication number	US-9618685-B2
Application number	US-201414580490-A
Country	US
Kind code	B2
Filing date	Dec 23, 2014
Priority date	Dec 26, 2013
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

Disclosed herein is a light guide plate formed by injection molding of an aromatic polycarbonate resin that is a polymer of an aromatic dihydroxy compound and a diaryl carbonate. The aromatic dihydroxy compound and the diaryl carbonate are present in a mole ratio of about 1:1.02 to about 1:1.35, and the aromatic polycarbonate resin has a weight average molecular weight from about 10,000 g/mol to about 18,000 g/mol and includes about 5 mol % to about 30 mol % of terminal hydroxyl groups relative to total moles of terminal groups. The light guide plate formed of the aromatic polycarbonate resin can reduce a yellowing phenomenon upon injection molding, can exhibit low color deviation under high temperature and high humidity conditions, and can secure excellent properties in terms of discoloration resistance, and brightness quality (brightness uniformity), and the like.

First claim

What is claimed is:

1. A light guide plate formed by injection molding of an aromatic polycarbonate resin that is a polymer of an aromatic dihydroxy compound and a diaryl carbonate,
wherein the aromatic dihydroxy compound and the diaryl carbonate are present in a mole ratio of about 1:1.02 to about 1:1.35,
wherein the aromatic polycarbonate resin has a weight average molecular weight from about 10,000 g/mol to about 18,000 g/mol and includes about 5 mol % to about 30 mol % of terminal hydroxyl groups relative to total moles of terminal groups, and
wherein the aromatic polycarbonate resin has a melt index (MI) of about 55 to about 165 g/10 minutes, as measured under conditions of about 300° C. and about 1.2 kgf in accordance with ASTM D1238.

2. The light guide plate according to claim 1 , wherein the light guide plate has a color deviation of about 0.005 to about 0.020, as measured after being left under conditions of about 80° C. and about 90% RH for about 500 hours, and a percentage (brightness uniformity) of lowest brightness to highest brightness of about 80% to about 95%.

3. The light guide plate according to claim 1 , wherein the light guide plate comprises a front surface, a rear surface facing the front surface and formed with an optical pattern, and side surfaces connecting the front surface to the rear surface.

4. The light guide plate according to claim 1 , wherein the side surface comprise a first side surface on which a light source is placed; a second side surface facing the first side surface; a third side surface connecting the first side surface to the second side surface; and a fourth side surface facing the third side surface and connecting the first side surface to the second side surface.

5. The light guide plate according to claim 1 , wherein the aromatic polycarbonate resin has a yellowness index variation (ΔYI) of about 0.5 to about 3.5 as represented by the following Expression 1:
Yellowness index variation (ΔYI)=YI 1 −YI 0   [Expression 1]

wherein YI 0 is a yellowness index of the aromatic polycarbonate resin (light guide plate) subjected to injection molding at an injection temperature (cylinder temperature) of about 340° C. and a mold temperature of about 70° C. according to a typical cycle time, and YI 1 is a yellowness index of the aromatic polycarbonate resin (light guide plate) subjected to injection molding under the same conditions (injection temperature of about 340° C. and a mold temperature of about 70° C.) after being left in a molten state for about 5 minutes within a cylinder.

6. A method of fabricating a light guide plate, comprising:
preparing an aromatic polycarbonate resin having a weight average molecular weight from about 10,000 g/mol to about 18,000 g/mol and a melt index (MI) of about 55 to about 165 g/10 minutes, as measured under conditions of about 300° C. and about 1.2 kgf in accordance with ASTM D1238 and including about 5 mol % to about 30 mol % terminal hydroxyl groups relative to total moles of terminal groups by polymerizing an aromatic dihydroxy compound and a diaryl carbonate in a mole ratio of about 1:1.02 to about 1:1.35; and
injection molding the aromatic polycarbonate resin.

7. The method according to claim 6 , wherein the injection molding comprises preparing a molten resin by heating the aromatic polycarbonate resin to an injection temperature (cylinder temperature) of about 320° C. to about 360° C., followed by injection molding the molten resin into a cavity of a mold having a mold temperature of about 50° C. to about 90° C. at an injection rate of about 300 mm/sec to about 800 mm/sec.

8. An aromatic polycarbonate resin for light guide plates, the aromatic polycarbonate resin being a polymer of an aromatic dihydroxy compound and a diaryl carbonate,
wherein the aromatic dihydroxy compound and the diaryl carbonate are present in a mole ratio of about 1:1.02 to about 1:1.35,
wherein the aromatic polycarbonate resin has a weight average molecular weight of about 10,000 g/mol to about 18,000 g/mol and includes about 5 mol % to about 30 mol % of terminal hydroxyl groups relative to total moles of terminal groups, and
wherein the aromatic polycarbonate resin has a melt index (MI) of about 55 to about 165 g/10 minutes, as measured under conditions of about 300° C. and about 1.2 kgf in accordance with ASTM D1238.

Assignees

• Samsung Sdi Co Ltd

Inventors

• Chi Jun Ho
• Chei Woo Suk
• Hur Jong Chan
• Lee Eun Byul
• Choi Kyu Buem

Classifications

• C08G64/307

  and phenols · CPC title

• B29D11/00663

  Production of light guides · CPC title

• G02B6/0035

  provided on the surface of the light guide or in the bulk of it · CPC title

• C08G64/06

  not containing aliphatic unsaturation · CPC title

• B29K2069/00

  Use of PC, i.e. polycarbonates {or derivatives thereof}, as moulding material · CPC title