JP2813131B2 - Backlight light guide plate using diffraction grating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight light guide plate suitable for achieving high brightness and uniformity of brightness on the upper surface of a liquid crystal backlight light guide plate.

[0002]

2. Description of the Related Art A conventional edge-type backlight light guide plate is formed on a back surface of the light guide plate with a dot printing or a grooving shape utilizing total reflection. Here, the light incident from one end of the light guide plate is made uniform over the entire upper surface of the light guide plate by changing the print pattern and the processing shape.

[0003]

In this case, an extreme contrast exists between a printed portion and a non-printed portion, and a portion subjected to total reflection and a portion not subjected to the total reflection. or
This is particularly noticeable when realizing a backlight light guide plate with higher brightness.

[0004] For this reason, finer pattern printing or shape processing can be considered, but in that case, their efficiency as a source of diffuse reflection or total reflection is reduced.

[0005]

Means for Solving the Problems The present invention utilizes a diffraction grating for diffracting light strongly despite its extremely fine shape for a light guide plate.

That is, a fine lattice stripe pattern is formed or printed (including transfer) on the rear surface of the light guide plate so as to interfere with light, and the light incident from one end of the light guide plate is diffracted toward the liquid crystal surface by the reflection grating. .

[0007] At this time, in order to uniformly irradiate the back surface of the light guide plate, the back surface of the light guide plate has a gradient of 0.5 ° to 5 °.

The operation of the diffraction grating (reflection grating) on the back surface of the backlight light guide plate can be explained as follows. That is, when light is applied to a diffraction grating formed or printed (including transfer) on the back surface of a flat light guide plate, as shown in FIG. 1, the diffraction angle (incident angle i; reflection angle θ) and the interval between the grid pattern d and wavelength of light λ
The following relational expression exists between.

(Sini−sin θ) = ± mλ / d (m = 0, 1, 2,...)

As is clear from this figure, the above equation is satisfied.
In the direction of θ, light interferes and becomes bright.

[0011]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The light guide plate according to the present invention has a structure as shown in FIG. 2 , and the light source (11) is a fluorescent tube having a cold cathode or a semi-hot electrode.

The light emitted from the light source impinges on the back surface of the plastic backlight light guide plate (12) with an inclination of 0.5 'to 5', and is formed or printed (including transfer) on the surface by diffraction. Diffracted in the direction of the liquid crystal display panel (14) by the function of the grating (13).

[0014] Since there is a tendency of 0.5'～5 'of the light guide plate back surface, the light from the light source is irradiated to the entire light guide plate back surface.

Meanwhile, to place the light source reflector (15) and for light guide plate reflector (16) to that the light from the light source around and the light guide plate back surface and the end surface of the light source leaks minimized is the same as the conventional .

In a fluorescent lamp for a backlight, red, green and blue light of three wavelengths are distributed as shown in FIG. 3, so if one type of diffraction grating is used, chromatic aberration occurs as shown in FIG. However, this can be solved by providing the light guide plate with a diffusion plate (17) or a light diffusion property. The same can be applied to the polarization of the diffraction grating.

The use of a condensing prism sheet (18) for increasing the brightness by utilizing the condensing action is also conventional.

[0018]

As described above, according to the present invention, the light from the fluorescent tube is converted into a diffraction grating having a very small unit shape (the pitch of the lattice pattern is from submicron to several tens of microns). The light guide plate surface can be made to shine evenly by the action, so that the surface brightness and the uniformity can be remarkably improved compared to the conventional method of processing the light guide plate sleeping surface using dot printing and total reflection. become.

[Brief description of the drawings]

FIG. 1 is a diagram showing a diffraction grating and light diffraction by the diffraction grating.

FIG. 2 shows an application of a diffraction grating to a backlight light guide plate,
Light from a fluorescent tube as idlight is uniformly distributed on the liquid crystal surface
General description of the schematic configuration of the present invention showing the method of diffracting
Cross section of Ming.

FIG. 3 shows the emission of a fluorescent tube normally used as a backlight light guide plate.
Spectral distribution of falling light.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 diffraction grating 2 incident light 3 diffracted light 11 light source (cold cathode or semi-hot electrode fluorescent tube) 12 plastic backlight light guide plate 13 diffraction grating (reflection grating) 14 liquid crystal display panel 15 light source reflector 16 light guide plate reflector 17 diffusion Plate 18 Condensing prism sheet

Claims (1)

(57) [Claims] 1. A plastic backlight light guide plate having a diffraction grating formed and printed (including transfer) on a back surface opposite to a liquid crystal.