KR100977272B1 - Light panel with light diffusion particles - Google Patents

Abstract

PURPOSE: A light panel with light diffusion particles is provided to concentrate light around a view angle distribution according to the direction of an optical pattern while improving the brightness and the uniformity of the brightness. CONSTITUTION: A pattern layer(110) has a plurality of optical patterns on one side. A plurality of optical diffusion particles(120) are dispersed inside an optical pattern of the pattern layer. The optical diffusion particles have a hollow shape and having an outer side which is formed with a material having a reference rate lower than the pattern layer.

Description

Light guide plate containing light diffusing particles {Light Panel with Light Diffusion Particles}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit of a liquid crystal display (LCD) device, and in particular, by providing an optical pattern and / or light diffusing particles in a lower part of a light guide plate, hot spots and bright lines are generated in the light incident part. The present invention relates to a light guide plate and a backlight unit using the same, which can prevent and improve luminance and luminance uniformity.

Recently, as the information society arrives, the demand for display devices is increasing in various forms. Accordingly, liquid crystal display (LCD), plasma display panel (PDP), electro luminescent display (ELD), and vacuum fluorescent display (VFD) Various flat panel display devices have been researched and developed. Here, LCD is widely used as a mobile flat panel display because of its excellent image quality, light weight, thinness, and low power consumption.

However, LCDs do not emit light by themselves and require a separate external light source to realize a high quality image. Therefore, the LCD structure further includes a backlight unit as a light source of the liquid crystal display panel in addition to the liquid crystal display panel, and the backlight unit uniformly supplies a high brightness light source to the liquid crystal display panel, thereby realizing high quality images.

In general, backlights of liquid crystal displays are classified into edge-lighting and direct-lighting backlights according to the manner in which the light sources are arranged.

Due to the relatively thin thickness, the side backlight is mainly used in LCDs for thinning portable communication devices, and the direct backlight is mainly used in LCDs for large screens such as notebooks or TV monitors due to high efficiency.

1 is a diagram illustrating a general side type backlight unit structure.

As shown in FIG. 1, the backlight unit 10 includes a light source 1, a reflecting plate 2, a light guide plate 3, a diffusion film 4, a first prism sheet 5, and a second prism sheet 6. And a protective sheet 7.

The light source 1 emits light for the first time, and includes cylindrical fluorescent lamps such as Cold Cathode Fluorescent Lamp (CCFL), Hot Cathode Fluorescent Lamp (HCFL), and External Electrode Fluorescent Lamp (EEFL), and LED (Light Emitting Diode) devices. EL (Electro Luminescent) elements and the like are used.

The light emitted from the light source 1 is incident on the light guide plate 3 to cause total reflection inside the light guide plate 3, and the light incident on the surface of the light guide plate 3 at an angle of incidence smaller than the critical angle is not totally reflected. Because it is transmitted without, it is emitted to the upper side and the lower side.

In this case, the reflector 2 reflects the light emitted downward and re-enters the light guide plate 3 to improve the light efficiency, and the diffuser film 4 diffuses the light emitted through the upper surface of the light guide plate 3. To make the luminance uniform and to widen the viewing angle.

The first prism sheet 5 is composed of a base portion 5-1 and a prism pattern arrangement portion 5-2 to firstly condense the light incident from the diffusion film 4 to vertically enter the LCD element. The second prism sheet 6 has the same configuration as that of the first prism sheet 5, and the second prism sheet 6 emits light by secondary condensing in order to increase the luminance uniformity of the light primarily collected in the first prism sheet 5. In order to improve luminance uniformity, the first prism sheet 5 and the second prism sheet 6 may be arranged such that the prism patterns of the first prism sheet 5 and the prism patterns of the second prism sheet 6 are perpendicular to each other. Is common.

The protective sheet 7 is positioned on the upper surface of the first prism sheet 5 or the upper surface of the second prism sheet 6 to generate scratches on the first prism sheet 5 or the second prism sheet 6. Prevent it.

As described above, the conventional backlight unit includes a reflector 2, a light guide 3, a diffusion film 4, a prism sheet 5, 6, and a protective sheet 7 to provide light in a direction perpendicular to the front of the LCD element. Since many parts, such as the manufacturing process is complicated, there is a problem that takes a lot of manufacturing costs.

A prism light guide plate may be used to form a prism on the rear surface of the light guide plate for high brightness and low cost. The prism light guide plate is a light guide plate having a fine pitch prism pattern formed on a rear surface thereof. When the prism light guide plate is used, even if only one inverted prism sheet is used instead of a plurality of prism sheets, the luminance may be higher than that of the conventional backlight unit.

2 is a diagram illustrating a structure of a backlight unit using a conventional prism light guide plate, and FIG. 3 is a diagram illustrating a luminance distribution of a backlight unit using a conventional prism light guide plate.

As illustrated in FIG. 2, the backlight unit 10 includes a prism light guide plate 13, a plurality of point light sources 23 disposed on one side of the prism light guide plate 13, and a reflector plate disposed on a bottom surface of the prism light guide plate 13. 27).

When light is irradiated from the point light source 23, the light is incident on the light incidence part 13a provided on the side of the prism light guide plate 13, and then reflected inside the prism light guide plate 13, so that the upper light exit part of the prism light guide plate 13 is formed. Exit through 13b). The light irradiated from the point light source 23 to the light incidence portion 13a generates a point-shaped light condensation portion having a relatively high light intensity near the light incidence portion 13a, and is caused by the prism pattern 16 of the prism light guide plate 13. Light collected in such a light condensing unit is spectroscopic, and bright lines are generated in an oblique direction (see FIG. 3).

In order to solve this problem, the prism is formed to be rounded or the prism pattern 16 is applied to the light incident portion 13a. However, there is a limit in removing such oblique lines. In particular, since the side light emitting unit is used in a notebook or a mobile phone, there is a problem that the prism light guide plate cannot be used due to the oblique line in the diagonal direction.

Accordingly, an object of the present invention is to prevent the occurrence of hot spots and bright lines generated at the light incidence portion of the light guide plate, to improve luminance and brightness uniformity, and to reduce the number of optical films used on the top surface of the light guide plate. It is an object of the present invention to provide a light guide plate having light diffusing particles which can reduce the unit manufacturing time and cost.

In order to achieve the above object, the light guide plate of the present invention includes a pattern part layer having a plurality of optical patterns formed on at least one surface in a light guide plate capable of emitting light incident from a side light source to an upper surface, and in the optical pattern of the pattern part layer. A plurality of light diffusing particles are dispersed and the refractive index of the base material of the pattern portion layer and the light diffusing particles is different.

In order to achieve the above object, the backlight unit of the present invention includes a side light source disposed on one side, and a light guide plate for emitting light incident from the side light source to an upper surface, wherein the light guide plate has a plurality of optical patterns on at least one surface thereof. The pattern part layer is formed, and a plurality of light diffusing particles are dispersed in the optical pattern of the pattern part layer, and the refractive indexes of the base material of the pattern part layer and the light diffusing particles are different.

Therefore, the backlight unit according to the present invention provides a light guide plate coated with light diffusing particles having diffusion and condensing effects, and thus, when a light guide plate having a plurality of optical patterns formed thereon is used, a bright line and a hot spot generated in a conventional backlight unit ( Appearance problems such as hot spots can be improved, and brightness uniformity can be improved.

In addition, when the light guide plate according to the present invention is used, instead of using a plurality of prism sheets, only one inverted prism sheet can be used to obtain higher luminance than a conventional backlight unit, thereby reducing the time and cost of manufacturing the backlight unit. There is a saving effect.

Hereinafter, a configuration of a light guide plate and a backlight unit according to the present invention will be described with reference to the drawings.

4A illustrates a side view and a light path of a backlight unit including a light guide plate according to a first embodiment of the present invention, and FIG. 4B illustrates a top view of the backlight unit including a light guide plate according to a second embodiment of the present invention. 4C is a top view of the backlight unit including the light guide plate according to the third embodiment of the present invention.

The backlight unit 1000 according to the present invention includes a light guide plate 100, a light source 200, and a reflector 300. The light guide plate 100 emits light incident from the side light source 200 to an upper surface, and includes a pattern part layer 110 having a plurality of optical patterns formed on at least one side thereof, and a plurality of lights in the optical pattern of the pattern part layer. Diffusion particles 120 are dispersed.

The light diffusing particles 120 are applied to the pattern part layer 110 so as to be integrated with each other, and the light diffusing particles 120 having a different refractive index from the base material of the pattern part layer 110 are coated to be dispersed.

Some of the light incident from the light source 200 disposed on one side of the light guide plate 100 is emitted to the upper part of the light guide plate 100, and a part of the light is transmitted in the transverse direction through the light guide plate 100. A part of the light transmitted in the lateral direction is refracted by the optical pattern or the light diffusing particles 120 formed in the pattern part layer 110 and transmitted to the upper part, or transmitted to the lower part and reflected from the reflecting plate to the upper surface. The pattern portion layer 110 of the light guide plate 100 may be formed only on the top or bottom surface of the light guide plate 100, as shown in FIGS. 4A and 4B, and as shown in FIG. 4C, together with the top and bottom surfaces thereof. The pattern part layers 110a and 110b formed on the upper and lower surfaces may be formed in parallel to each other or vertically.

5A to 5D illustrate the shape of an optical pattern formed on a pattern portion layer of a light guide plate according to an embodiment of the present invention. The optical pattern includes a polygonal pattern (FIGS. 5A and 5B) and a polygonal pattern having a curved upper surface ( 5C) and an arc pattern (FIG. 5D).

6A illustrates a method of manufacturing a light guide plate according to an embodiment of the present invention, and FIG. 6B illustrates a method of manufacturing a light guide plate according to another embodiment of the present invention.

In the method of manufacturing the light guide plate according to the present invention, as shown in FIG. 6A, an optical pattern (in one embodiment, a triangular prism pattern) is formed on a substrate (for example, PET: Poly Ethylene Terephthalate), and then light is diffused. After the particles 120 are dispersed, and as shown in FIG. 6B, a coating layer (eg, a UV resin including light diffusing beads) including the light diffusing particles 120 is formed on the substrate 110. There is a method of molding an optical pattern. The coating layer may be formed by irregularly dispersing light diffusing particles, which are fine particles, by coating and curing a coating liquid containing light diffusing particles, and the light diffusing particles may be formed by refracting or transmitting light transmitted therethrough. To diffuse uniformly.

7A and 8A illustrate the shape of light diffusing particles included in a light guide plate according to an embodiment of the present invention, and FIGS. 7B and 8B illustrate the light diffusing particles included in a light guide plate according to an embodiment of the present invention. The figure which shows the result of simulating the light diffusivity according to the form.

The light diffusing particles according to the present invention may be formed in various forms such as hollow spheres, hollow spheres, polygonal shapes, and the like, and the material of the light diffusing particles may be glass, acrylic, nylon, or silicon-based compounds, or the materials. It may be composed of a compound containing at least one. Preferably, the light diffusion particles have a hollow, the outer shell may be made of a material having a refractive index smaller than the pattern portion layer. Most preferably, the shell of the light diffusing particles may be formed of glass bubbles made of glass and the hollows produced in vacuum.

Referring to the embodiment shown in FIG. 7A, the pattern portion layer A including the light diffusing particles is formed of a material having a refractive index of 1.58, and the light diffusing particles B have a hollow shape and have a refractive index of 1.52. It is formed of a material. Referring to the light diffusivity shown in FIG. 7B, light incident from the point light source is refracted or reflected through the pattern sublayer and the light diffusing particles having different refractive indices.

Referring to another embodiment illustrated in FIG. 8A, the pattern portion layer A including the light diffusing particles is formed of a material having a refractive index of 1.58, and the light diffusing particles B have a hollow sphere and have a refractive index of 1.52. It is formed of a phosphorous material and is maintained in a vacuum state with a refractive index of 1.00 in the hollow. Referring to the light diffusivity shown in FIG. 8B, the light incident from the point light source is primarily refracted or reflected at the surface of the light diffusing particles and the pattern sublayer having different refractive indices, and is transmitted to the hollow inside the light diffusing beads. Refraction or reflection is achieved differentially. Therefore, the light transmitted from the point light source can be diffused into a uniform surface light source.

The backlight unit according to the present invention includes a side light source disposed on one side, and a light guide plate for emitting the light incident from the side light source to the upper surface, the light guide plate is provided with a pattern portion layer formed with a plurality of optical patterns on one side In the optical pattern of the pattern part layer, a plurality of light diffusing particles are dispersed, and the refractive indexes of the base material of the pattern part layer and the light diffusing particles are different.

The backlight unit may further include an inverted prism sheet disposed on the light guide plate, the prism being formed in a direction perpendicular to the extension direction of the plurality of optical patterns formed on the light guide plate to collect light diffused on the light guide plate. have.

The brightness of the backlight unit is determined according to the size and content of the light diffusing particles dispersed in the pattern portion layer of the light guide plate. That is, the light diffusivity may vary depending on the size and content of the light diffusing particles, thereby determining the turbidity, the light transmittance, the average luminance, and the light uniformity.

The light-diffusing particle content in the optical pattern of the pattern portion layer of the light guide plate according to the present invention is characterized in that it is contained in a ratio of 1% or more and 27% or less with respect to the coating layer for fixing the light diffuser particles. In addition, the size of the light-diffusing particles is characterized in that the ratio of the height of the optical pattern to the diameter length of the light-diffusing particles is formed in more than 0.5% to 15%.

The relationship between the content, turbidity, and transmittance of the light diffusing particles is shown in [Table 1], and the light transmittance must be 90% or more to be utilized as a backlight unit. Here, the content of the light diffusing particles is calculated as (volume of the light diffusing particles / volume of the coating layer) * 100.

Light Diffusion Particle Content Haze Transmittance 0% 5% 99% One% 80% 96% 3% 82% 95% 5% 85% 95% 7% 87% 95% 9% 90% 94% 11% 93% 94% 13% 95% 93% 15% 98% 93% 17% 98% 92% 19% 98% 92% 21% 98% 91% 23% 98% 91% 25% 98% 90% 27% 98% 90% 29% 99% 89% 31% 99% 89% 33% 99% 88%

Therefore, in order for the light transmittance of the backlight unit according to the present invention to be maintained at 90% or more, the content of the light diffusing particles is preferably contained in a ratio of 1% or more and 27% or less with respect to the coating layer. That is, when the light diffusing particle content exceeds 27%, the light transmittance of the backlight unit may be 90% or less, which may cause a problem of deterioration in brightness. When the light diffusing particle content is less than 1%, the turbidity becomes less than 80%. There is a problem that the function of diffusing light cannot be sufficiently performed.

The relationship between the size of the light diffusing particles included in the light guide plate according to the present invention and the height of the optical pattern of the pattern part layer is shown in Table 2, and the size of the light diffusing particles is 90% or more in average luminance and 80% in light uniformity. It is preferable to be formed above.

Size of Light Diffusion Particles Average luminance Uniformity 0% 100% 65% 0.3% 98% 70% 0.5% 96% 80% One% 95% 81% 3% 94% 82% 5% 94% 83% 7% 93% 85% 9% 93% 89% 11% 93% 93% 13% 91% 93% 15% 90% 93% 17% 89% 92% 19% 88% 92%

That is, the size (%) of the light diffusing particles is calculated as (the diameter of the light diffusing particles / the height of the optical pattern) * 100, the height of the optical pattern as shown in Figure 9, when the optical pattern is a triangular prism pattern It means the length from the bottom to the vertex of the triangular prism pattern, in the case of the polygon shape means the length from the lowest point to the highest point of the optical pattern.

The average luminance (%) represents the sum of the luminance values of the points measuring the luminance divided by the number of measurement points as a percentage, and the luminance uniformity (%) is the minimum luminance value among the luminance values of the measurement points. The value divided by the value is multiplied by 100 (see FIG. 10).

Therefore, in order for the backlight unit according to the present invention to have an image quality characteristic of 90% or more of average luminance and 80% or more of uniformity, the length of the diameter of the light diffusing particles to the height of the optical pattern is preferably 0.5% or more and 15% or less. That is, when less than 0.5%, the uniformity is lowered, and when it exceeds 15%, the average brightness is lowered, which causes a problem that the product quality is not satisfied.

In addition, the pattern portion layer is formed as the optical pattern is densely spaced apart from any one side to improve the light diffusion effect, characterized in that the light diffusion particles are disposed between the optical pattern of the pattern layer portion. . That is, a plurality of light diffusing particles formed between the optical patterns of the pattern portion layer protruding toward the reflecting plate side are formed, and serves to diffuse the light transmitted from the light source to the top.

FIG. 11A illustrates a light incidence part of a backlight unit using a general prism light guide plate, and FIG. 11B illustrates a light incidence part of a backlight unit using a light guide plate according to the present invention.

In the case of a backlight unit using a general prism light guide plate, an oblique line of light is generated in the light incident part, so that the light incident part of the backlight unit using the light guide plate according to the present invention can observe uniform light diffusion.

On the other hand, the present invention is not limited to the above-described typical preferred embodiment, but can be carried out in various ways without departing from the gist of the present invention, various modifications, alterations, substitutions or additions in the art Anyone who has this can easily understand it. If such improvement, change, substitution or addition is carried out within the scope of the appended claims, the technical spirit should also be regarded as belonging to the present invention.

1 is a diagram illustrating a general side type backlight unit structure.

2 is a diagram illustrating a structure of a backlight unit using a conventional prism light guide plate.

3 is a diagram illustrating luminance distribution of a backlight unit using a conventional prism light guide plate.

4A illustrates a side view and a light path of a backlight unit including a light guide plate according to a first embodiment of the present invention, and FIG. 4B illustrates a top view of the backlight unit including a light guide plate according to a second embodiment of the present invention. 4C is a top view of the backlight unit including the light guide plate according to the third embodiment of the present invention.

5A to 5D illustrate the shape of an optical pattern formed on a pattern portion layer of a light guide plate according to an embodiment of the present invention.

6A illustrates a method of manufacturing a light guide plate according to an embodiment of the present invention, and FIG. 6B illustrates a method of manufacturing a light guide plate according to another embodiment of the present invention.

FIG. 7A illustrates the shape of light diffusing particles included in a light guide plate according to an embodiment of the present invention, and FIG. 7B illustrates light diffusing degree according to the shape of light diffusing particles included in a light guide plate according to an embodiment of the present invention. It is a figure which shows the result of a simulation.

FIG. 8A illustrates the shape of light diffusing particles included in a light guide plate according to an embodiment of the present invention, and FIG. 8B illustrates light diffusing degree according to the shape of light diffusing particles included in a light guide plate according to an embodiment of the present invention. It is a figure which shows the result of a simulation.

9 is a view for explaining the length to the vertex of the optical pattern of the pattern portion layer according to the present invention.

10 is a view for measuring the luminance uniformity and the average luminance of the backlight unit according to the present invention.

FIG. 11A illustrates a light incident part of a backlight unit using a general light guide plate, and FIG. 11B is a view illustrating a light incident part of a backlight unit using a light guide plate according to the present invention.

Claims (9)

In the light guide plate which can emit the light incident from the side light source to the upper surface, A pattern part layer having a plurality of optical patterns formed on at least one surface is provided, A plurality of light diffusing particles are dispersed in the optical pattern of the pattern portion layer, The light diffusing particle has a hollow, the light diffusing particle is a light guide plate, characterized in that the outer skin is made of a material having a refractive index smaller than the pattern portion layer. The method of claim 1, The light diffusing particle is a light guide plate, characterized in that made of a polymer or glass. delete The method of claim 1, A light guide plate having a content of light diffusing particles in the optical pattern of the pattern portion layer of 1% or more and 27% or less. The method of claim 1, The size of the light diffusing particles is a light guide plate, characterized in that the ratio of the height of the optical pattern to the diameter length of the light diffusing particles is formed from 0.5% to 15%. A side light source disposed on one side; And It includes a light guide plate for emitting the light incident from the side light source to the upper surface, The light guide plate includes a pattern part layer having a plurality of optical patterns formed on at least one surface, and a plurality of light diffusing particles are dispersed in the optical pattern of the pattern part layer. The light diffusing particle has a hollow, the light diffusing particle is a backlight unit, characterized in that the outer skin is made of a material having a refractive index smaller than the pattern portion layer. The method of claim 6, And an inverted prism sheet disposed on the light guide plate, the plurality of prisms being formed to be perpendicular to a direction in which the plurality of optical patterns formed on the light guide plate extend, to collect light diffused to the upper portion of the light guide plate. Backlight unit. delete The method of claim 6, The content of the light diffusion particles in the pattern portion layer is 1% or more and 27% or less, and the size of the light diffusion particles is such that the ratio of the optical pattern to the diameter length of the light diffusion particles is 0.5% or more and 15% or less. The backlight unit, characterized in that formed.

Images