US20060291236A1

US20060291236A1 - Light guide plate with translucent ink film, and backlight module and liquid crystal display device using the same

Info

Publication number: US20060291236A1
Application number: US11/474,585
Authority: US
Inventors: Yu-Ju Hsu; Jui-Hua Hsieh
Original assignee: Innolux Display Corp
Current assignee: Innolux Corp
Priority date: 2005-06-24
Filing date: 2006-06-26
Publication date: 2006-12-28
Also published as: TW200700834A

Abstract

A light guide plate (200) includes at least one surface through which light beams pass, at least one translucent ink film (220) disposed on the at least one surface through which light beams pass, and the at least one translucent ink film includes a plurality of pigment particles (221). The pigment particles of the translucent ink film can absorb red light and green light, and thereby compensate for a shift in chromaticity that would otherwise occur in a backlight module due to absorption of blue light in the optical sheets of the backlight module. Therefore degradation of the display quality of the LCD is reduced or even eliminated.

Description

FIELD OF THE INVENTION

The present invention relates to light guide plates, backlight modules that include a light guide plate, and liquid crystal display devices that include a backlight module.

GENERAL BACKGROUND

Conventionally, a liquid crystal display (LCD) device includes a backlight module, a liquid crystal panel, and a frame for accommodating the backlight module and the liquid crystal panel. The backlight module supplies light beams to the liquid crystal panel to display images.
FIG. 5 is a schematic, exploded, side view of a conventional backlight module 100. The backlight module 100 includes a first diffusion sheet 160, a brightness enhancement sheet 150, a second diffusion sheet 140, a light guide plate 130, and a reflection sheet 110 arranged in that order from top to bottom. The light guide plate 130 includes an emitting surface 131, a bottom surface 132, and an incident surface 133. The backlight module 100 further includes a light source 170 disposed adjacent to the incident surface 133 of the light guide plate 130. The first and second diffusion sheets 160, 140 and the brightness enhancement sheet 150 are two kinds of optical sheets.
Light beams emitted by the light source 170 transmit into the light guide plate 130 via the light incident surface 133, and then pass through the emitting surface 131 of the light guide plate 130, the second diffusion sheet 140, the brightness enhancement sheet 150, and the first diffusion sheet 160 to illuminate a display device employing the backlight module 100. Thereby, the display device can display images.
However, any one or more of the optical sheets may partly absorb the light beams passing therethrough. Commonly, the optical sheets mainly absorb light beams with short wavelengths. Thus a portion of blue light beams is absorbed, and the chromaticity of emitting light beams is biased toward yellow. The shift in the chromaticity may degrade the display quality of the display device employing the backlight module 100.
What is needed, therefore, is a backlight module and a display device using the same that overcome the above-described deficiencies.

SUMMARY

A light guide plate includes at least one surface through which light beams pass, at least one translucent ink film disposed on the at least one surface through which light beams pass, and the at least one translucent ink film includes a plurality of pigment particles.
A backlight module includes a light guide plate having an incident surface and at least one other surface through which light beams pass, and at least one translucent ink film disposed on at least one of the incident surface and the at least one other surface through which light beams pass, the at least one translucent ink film having a plurality of pigment particles. A light source is disposed adjacent to the incident surface of the light guide plate.
A liquid crystal display device includes a top and bottom substrate opposite to each other, a liquid crystal layer sandwiched between the substrates, and the backlight module as described above disposed adjacent to the bottom substrate.
Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, all the views are schematic.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a light guide plate according to a first embodiment of the present invention.
FIG. 2 is an exploded, side view of a backlight module incorporating a light guide plate according to a second embodiment of the present invention.
FIG. 3 is a schematic, side view of a backlight module incorporating a light guide plate similar to that of the first embodiment.
FIG. 4 is a schematic, side view of a liquid crystal display device incorporating the backlight module of FIG. 3.
FIG. 5 is an exploded, side view of a conventional backlight module.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a schematic, side view of a light guide plate according to a first embodiment of the present invention. The light guide plate 200 includes a substrate 230, and a translucent ink film 220 formed on the substrate 230. The substrate 230 includes an incident surface 233, an emitting surface 231, and a bottom surface 232. The emitting surface 231 and the bottom surface 232 are opposite to each other. The incident surface 233 adjoins the emitting surface 231 and the bottom surface 232. The translucent ink film 220 is formed on the emitting surface 231.
A thickness of the translucent ink film 220 is in the range from 1 mm to 100 mm, and it can be printed or coated on the substrate 230. The light guide plate 200 is typically made from polyethylene terephthalate (PET), polycarbonate (PC), or polymethyl methacrylate (PMMA). A base material of the translucent ink film 220 is translucent resin, which can for example be PMMA. The translucent ink film 220 includes a plurality of pigment particles 221 embedded in the base material. The pigment particles 221 are blue pigment particles or other tiny pigment particles which can absorb red light and green light, such as blue dye particles. The pigment particles 221 are spherical, and their size is in the range from 1 μm to 100 μm. The pigment particles 221 can compensate for a shift in chromaticity that would otherwise occur in an associated backlight module due to absorption of blue light in optical sheets of the backlight module.
In an alternative embodiment, a second translucent ink film 220 can be formed on the bottom surface 232 of the light guide plate 200.
FIG. 2 is a schematic, exploded, side view of a backlight module 300 incorporating a light guide plate according to a second embodiment of the present invention. The backlight module 300 includes a first diffusion sheet 360, a brightness enhancement sheet 350, a second diffusion sheet 340, a light guide plate 330, a translucent ink film 320, and a reflection sheet 310 arranged in that order from top to bottom. The light guide plate 330 includes an emitting surface 331, a bottom surface 332, and an incident surface 333. The emitting surface 331 and the bottom surface 332 are opposite to each other. The incident surface 333 adjoins the emitting surface 331 and the bottom surface 332. The backlight module 300 further includes a light source 370 disposed adjacent to the incident surface 333 of the light guide plate 330. The first and second diffusion sheets 360, 340 and the brightness enhancement sheet 350 are two or three kinds of optical sheets.
The translucent ink film 320 is formed on the bottom surface 332. A thickness of the translucent ink film 320 is in the range from 1 mm to 100 mm. The translucent ink film 320 includes a plurality of pigment particles 321. The pigment particles 321 are blue pigment particles or other tiny pigment particles which can absorb red light and green light. The pigment particles 321 can compensate for a shift in chromaticity that would otherwise occur in the backlight module 300 due to absorption of blue light in the optical sheets 340, 350, 360 of the backlight module 300.
In an alternative embodiment, a second translucent ink film 320 can be formed on the emitting surface 331 of the light guide plate 330.
FIG. 3 is a schematic, exploded, side view of a backlight module 400 incorporating a light guide plate that is similar to the light guide plate of FIG. 1. The backlight module 400 is similar to the backlight module 300 of FIG. 2. However, the backlight module 400 includes the light guide plate 430, a translucent ink film 420, and a plurality of light sources 470. The light guide plate 430 has an emitting surface 431 and an opposite incident surface 432. The translucent ink film 420 is formed on the emitting surface 431, and includes a plurality of pigment particles 421. The light sources 470 are disposed adjacent to the incident surface 432 of the light guide plate 430.
FIG. 4 is a schematic, exploded, side view of a liquid crystal display device incorporating the backlight module of FIG. 3. The liquid crystal display device 500 includes a top substrate 582, a bottom substrate 581, a liquid crystal layer 590 sandwiched between the substrates 581, 582, and the backlight module 400. The backlight module 400 is disposed adjacent to the bottom substrate 581.
The pigment particles 421 of the translucent ink film 420 can absorb red light and green light, and thereby compensate for a shift in chromaticity that would otherwise occur in the backlight module 400 due to absorption of blue light in the optical sheets of the backlight module 400. Therefore degradation of the display quality of the LCD 500 is reduced or even eliminated.
It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A light guide plate, comprising:

at least one surface through which light beams pass; and

at least one translucent ink film disposed on the at least one surface through which light beams pass;

wherein the at least one translucent ink film comprises a plurality of pigment particles.

2. The light guide plate as claimed in claim 1, wherein pigment particles are blue pigment particles.

3. The light guide plate as claimed in claim 1, wherein a thickness of the at least one translucent ink film is in the range from 1 mm to 100 mm.

4. The light guide plate as claimed in claim 1, further comprising an emitting surface, a bottom surface opposite to the emitting surface, and an incident surface between the emitting surface and a bottom surface, wherein the at least one surface through which light beams pass is selected from the group consisting of the emitting surface and the bottom surface.

5. The light guide plate as claimed in claim 4, wherein the at least one translucent ink film is disposed on the emitting surface.

6. The light guide plate as claimed in claim 4, wherein the at least one translucent ink film is disposed on the bottom surface.

7. The light guide plate as claimed in claim 1, further comprising an emitting surface and an incident surface opposite to the emitting surface, wherein the at least one surface through which light beams pass is selected from the group consisting of the emitting surface and the incident surface.

8. The light guide plate as claimed in claim 7, wherein the at least one translucent ink film is disposed on the incident surface.

9. The light guide plate as claimed in claim 2, wherein the blue pigment particles are blue dye particles.

10. The light guide plate as claimed in claim 1, wherein the pigment particles are spherical, and sizes of the pigment particles are in the range from 1 μm to 100 μm.

11. A backlight module, comprising:

a light guide plate, comprising an incident surface and at least one other surface through which light beams pass, and at least one translucent ink film disposed on at least one of the incident surface and the at least one other surface through which light beams pass, the at least one translucent ink film comprising a plurality of pigment particles; and

a light source disposed adjacent to the incident surface of the light guide plate.

12. The backlight module as claimed in claim 11, wherein the pigment particles are blue pigment particles.

13. The backlight module as claimed in claim 11, wherein a thickness of the translucent ink film is in the range from 1 mm to 100 mm.

14. The backlight module as claimed in claim 11, wherein the light guide plate further comprises an emitting surface and a bottom surface opposite to the emitting surface, wherein the incident surface is between the emitting surface and the bottom surface, and the at least one other surface through which light beams pass is selected from the group consisting of the emitting surface and the bottom surface.

15. A liquid crystal display device, comprising:

a top substrate and a bottom substrate opposite to each other;

a liquid crystal layer sandwiched between the substrates; and

a backlight module disposed adjacent to the bottom substrate, the backlight module comprising:

a light guide plate comprising an incident surface and at least one other surface through which light beams pass, and at least one translucent ink film disposed on at least one of the incident surface and the at least one other surface through which light beams pass, the at least one translucent ink film comprising a plurality of pigment particles; and

16. The liquid crystal display device as claimed in claim 15, wherein the pigment particles are blue pigment particles.

17. The liquid crystal display device as claimed in claim 15 wherein a thickness of the at least one translucent ink film is in the range from 1 mm to 100 mm.