KR101158053B1 - Light diffusion plate with the improved brightness - Google Patents

Abstract

The present invention provides a diffuser plate having a two-layer structure in which the difference in refractive index between the incident layer of the light using organic or inorganic diffusion particles and the resin satisfies ± 0.05 and the light exit layer using the particles serving as the lens is coextruded. This may enable a thin backlight device having improved brightness compared to a single layer diffuser plate with improved brightness at the front side.

Description

Light diffusion plate with the improved brightness             

1 is a diagram illustrating the light emitted to the diffusion plate according to the present invention.

    <Description of Major Symbols in Drawing>

1-incident layer of light 2-emitting layer of light

20-particle

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffuser plate with improved luminance characteristics, and more particularly to a diffuser plate used in a lighting cover, an advertisement panel, and in particular, a direct backlight type liquid crystal display.

Conventionally, the backlight in the liquid crystal display uses an edge light method and a direct type method.

In the edge light method, a fluorescent lamp is disposed at the edge of the light guide plate, and the bottom of the light guide plate is manufactured in an inclined structure to attach a reflecting plate. If necessary, a pattern may be formed on the bottom of the light guide plate through printing. This approach is inevitable for low brightness and is mainly applied to small size displays.

The direct type method does not mainly use a light guide plate, but a plurality of lamps are installed on a reflecting plate, and a diffuser plate is arranged at a certain distance thereon.

Here, the diffusion plate is manufactured by melting and extruding the plastic resin chip, and includes organic or inorganic particles that scatter light in order to conceal the lamp and make light of uniform brightness. In this case, the scattered light has more components in the parallel direction than components in the vertical direction of the diffuser plate, so that the disadvantage of deterioration of brightness at the front part cannot be avoided. That is, the amount of light irradiated to the liquid crystal panel of the front portion is reduced.

Accordingly, the present inventors have been trying to develop a diffuser plate capable of enabling a thin backlight device having improved front surface luminance compared to a conventional diffuser plate, and together with a resin with a general diffusion layer containing ordinary organic or inorganic particles. As a result of coextrusion using particles having a refractive index difference within a certain range on the light exit surface, particles on the light exit surface act as a lens to collect light in the vertical direction of the diffuser plate, resulting in improved luminance. The present invention was completed.

Accordingly, the present invention provides a diffuser plate useful for an advertising panel and a direct-backlit liquid crystal display requiring a particularly thin thickness, as well as an illuminating cover for which the brightness is improved and especially the front part brightness is required.

Diffusion plate of the present invention for achieving the above object is an incident layer of light using organic or inorganic diffusion particles; And a refractive index difference from the resin satisfying ± 0.05 and having a two-layer structure in which the light emitting layer using the particles serving as the lens is coextruded.

The present invention will be described in more detail as follows.

The structure of the diffuser plate according to the present invention is schematically shown in FIG. 1, and has a two-layer structure of an incident layer 1 of light and an emission layer 2 of light.

(1) incident layer of light

The incident layer 1 of light is obtained by extruding together with the resin using organic or inorganic particles such as a conventional diffusion plate, and is a diffusion layer that serves to diffuse the incident light.

Particles that serve to diffuse light, such as organic particles and inorganic particles used here is a degree known to those skilled in the art, and the resin is also well known in the manufacture of the diffusion plate, so there is no limitation.

(2) light exit floor

In particular, the present invention has a light emitting layer 2 formed by co-extrusion with the light incident layer 1, which specifically uses particles that act as a lens while having a refractive index difference of ± 0.05. And coextruded together with the incident layer of light.

The light emitting layer 2 is a layer that collects diffused light, unlike the light incident layer 1, and the particle 20 of the light emitting layer should use a difference in refractive index of ± 0.05 from the resin. There is no significant effect on the direction of light inside, and only the path of light emitted can be changed.

Specifically, particles having a refractive index of 1.40 to 1.60 are preferred, which generally takes into account the refractive index of various plastic resins used in the manufacture of the diffusion plate.

As an example, when using an acrylic resin, it is preferable to use the particle | grains whose refractive index is 1.49-1.50.

The particles may be glass particles or organic particles, provided that they can act as lenses while satisfying the difference in refractive index with the resin as described above.

The size of the particles is not limited but is preferably 0.2 to 50 µm. If the size of the particles is smaller than 0.2 μm, the surface of the emission layer may be too rough if the size of the particles is insufficient to perform the lens role and larger than 50 μm.

In addition, the content of the particles is appropriately 0.1 to 20% by weight in the exit layer composition, preferably about 10% by weight. When the content of the particles is too small, it is difficult to achieve the desired purpose, if the content is more than 20% by weight may be technically difficult to extrude.                     

The thickness of the light emitting layer using such particles is preferably 5 to 50% of the total thickness of the diffuser plate. It is difficult under the coextrusion technique to make the thickness thinner than 5% of the thickness of the diffuser plate. In comparison, the content of the diffusing agent is increased, which may cause mechanical imbalance between the incident layer and the exit layer, which may cause a problem of increasing residual stress.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Example 1

Extrusion is carried out using the same diffusion particles as in the conventional diffusion plate production to obtain the lower end of the diffusion plate, and the light is emitted to the upper end using a glass particle having a particle diameter of 5㎛ and a refractive index difference of 0 to the resin 10% by weight The discharge rate of each extruder was adjusted while making it 0.2 mm, and as a result, the diffuser plate of thickness 2mm was obtained. At this time, by adjusting the content of the diffusion particles at the lower end of the diffusion plate was produced so that the transmittance of 63%.

Example 2

A diffusion plate was manufactured in the same manner as in Example 1 except that the upper end portion was obtained using organic particles having a difference in refractive index of 0.02 from the resin.

Example 3

A diffusion plate was manufactured in the same manner as in Example 1, except that the upper end portion was obtained using organic particles having a particle diameter of 10 μm.

Example 4

A diffusion plate was manufactured in the same manner as in Example 1, except that the thickness of the upper end part was 0.1 mm to obtain a diffusion plate having a total thickness of 2 mm.

Comparative Example 1

Unlike Example 1, a single layer diffusion plate was extruded using the same diffusion particles as in Example 1 to obtain a diffusion plate having a thickness of 2 mm and a transmittance of 63%.

Experimental Example

9 points commonly used for measuring luminance of a backlight unit by cutting a diffuser plate obtained in accordance with Examples 1 to 4 and Comparative Example 1 to a size of 26 inches and placing 12 cold-cathode fluorescent lamps on a device arranged at regular intervals. Luminance measurements were taken.

Average brightness is shown in Table 1 below.

Example Comparative Example 1 One 2 3 4 Brightness (cd / ㎡) 7616 7580 7560 7630 7186

From the results in Table 1, as shown in Examples 1 to 4, in the case of the diffusion plate of the two-layer structure obtained by coextrusion using particles having a difference in refractive index with the resin satisfying a specific category, the luminance was improved by about 5.2 to 6.2%. It can be seen that.

As described in detail above, the diffusion plate obtained by coextrusion with a conventional light diffusion layer using particles having a refractive index difference of ± 0.05 with resin in the layer where light is emitted according to the present invention is applied to a single layer diffusion plate. In comparison, the luminance may be improved to enable a thin backlight device having improved front luminance.

Claims (7)

In the diffusion plate extruded using a plastic resin chip and particles, The difference in refractive index between the incident layer of the light using organic or inorganic diffusion particles and the resin satisfies ± 0.05, and the light exiting layer using the particles serving as the lens is coextruded to have a two-layer structure. The content of the particles in the light emitting layer is a diffusion plate, characterized in that 10 to 20% by weight of the light emitting layer composition. The diffuser plate according to claim 1, wherein the light emitting layer has a thickness corresponding to 5 to 50% of the total thickness of the diffuser plate. The diffusion plate according to claim 1, wherein the particles have a refractive index of 1.40 to 1.6 in the light emitting layer. The diffusion plate according to claim 1, wherein the resin is an acrylic resin and the particles used in the light emitting layer are glass particles having a refractive index of 1.49 to 1.50. The diffusion plate according to claim 1, wherein the particles in the light emitting layer are organic particles. delete The diffusion plate according to claim 1, wherein the size of the particles in the light emitting layer is 0.1 to 50 µm.

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