KR20080063986A - Diffusion sheet for wavelength changing and backlight unit using the same - Google Patents

Abstract

A diffusion sheet for changing a wavelength and a backlight unit using the same are provided to enhance diffusion of light inputted to an optical excitation layer by including a phosphor of the optical excitation layer in a particulate type. A diffusion sheet(20) for changing a wavelength includes an optical excitation layer(22) and a light diffusion layer(21). The optical excitation layer absorbs an incident light, emits light with a wavelength different from that of the absorbed light, and is formed by mixing a phosphor with transparent resin. The light diffusion layer is formed to face the optical excitation layer and scatters and diffuses the incident light. The diffusion sheet for changing the wavelength further includes a base layer(23) which is formed between the optical excitation layer and the light diffusion layer and has a light-transmitting property.

Description

Diffusion sheet for wavelength conversion and backlight unit using the same {DIFFUSION SHEET FOR WAVELENGTH CHANGING AND BACKLIGHT UNIT USING THE SAME}

1 is a cross-sectional view of a wavelength conversion diffusion sheet according to an embodiment of the present invention.

2 is a cross-sectional view of a wavelength conversion diffusion sheet according to another embodiment of the present invention.

3 and 4 are cross-sectional and exploded perspective views illustrating a backlight unit according to an embodiment of the present invention.

5 is an exploded perspective view of a backlight unit according to another embodiment of the present invention.

<Code Description of Main Parts of Drawing>

11,21: light diffusion layer 12,22: light excitation layer

23: substrate layer 112, 512: substrate

114,514: light source 140,540: reflector

120,520: Light guide plate 150,550: Diffusion sheet for wavelength conversion

151,551: Prism Sheet

The present invention relates to a wavelength conversion diffusion sheet and a backlight unit using the same, and more particularly, to a wavelength conversion diffusion sheet and a backlight unit using the same by employing an optical excitation layer in the diffusion sheet. It is about.

In general, flat displays are classified into light emitting and light receiving types. An example of a light-receiving flat panel display is a liquid crystal display. The liquid crystal display itself does not emit light to form an image, but light is incident from outside to form an image. It cannot be observed.

Therefore, a back light unit is installed on the back of the liquid crystal display to irradiate light. Such a backlight unit is used for a surface light source device such as an illumination signboard in addition to a light receiving display such as a liquid crystal display.

The backlight unit may include a direct light type (LGP) and a light guide panel (LGP) in which a plurality of lamps disposed directly below the liquid crystal display device directly irradiate light to the liquid crystal panel according to the arrangement of the light sources. Lamps installed on the edge side are classified into edge light types that irradiate light and transmit it to the liquid crystal panel.

The edge emitting type backlight unit uses a line light source and a point light source as a light source, and a typical cathode light source includes a cold cathode fluorescent lamp (CCFL) in which electrodes at both ends are installed in a tube, and a light source is a light source. There is a light emitting diode (LED).

Here, the CCFL has the advantage that it can emit strong white light, obtain high brightness and high uniformity, and can be designed with a large area, but it is operated by a high frequency AC signal and has a narrow operating temperature range.

In contrast, the LED is operated by a DC signal, has a long life and has a wide operating temperature range. However, in order to use such an LED as a backlight unit or general lighting, it is necessary to obtain white light using the LED.

As a method of implementing a white LED, there is a method of implementing white by combining three LEDs emitting red, green, and blue, which are three primary colors of light. However, this method requires the use of three LEDs to create one white light source, and involves the hassle of controlling each LED.

Second, a method of realizing white by exciting a yellow phosphor by using a blue LED as a light source, or a method of exciting a trichromatic phosphor by using an ultraviolet light emitting LED as a light source. In general, this method is a method of applying a fluorescent material and a transparent resin in the LED package, there is a problem that the process is complicated and the volume of the LED package is large because the process of injecting the phosphor should be accompanied.

In particular, when the LED package including the fluorescent material is employed in the backlight unit as described above, the light scattered from the phosphor is reabsorbed by the LED chip, and the light extraction efficiency is lowered. There is a problem that the reliability is lowered.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to provide a wavelength conversion diffusion sheet and a backlight unit using the same by employing an optical excitation layer in the diffusion sheet and improving luminance, luminance uniformity and color uniformity. .

In order to achieve the above technical problem, one aspect of the present invention,

Absorbs the light emitted and emits light having a wavelength different from that of the absorbed light, and is formed to be opposite to the light excitation layer and the light excitation layer formed by mixing a phosphor and a transparent resin, and scatters and diffuses the received light. Provided is a diffusion sheet for converting wavelengths including a light diffusion layer.

Preferably, the light-transmitting layer and the light diffusing layer may further include a light-transmitting base layer, in this case, the base layer is polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polyester, polycarbonate It is preferably made of a material selected from the group consisting of synthetic resins of polystyrene, polyolefin, cellulose acetate and weather resistant vinyl chloride.

The light diffusion layer is preferably made of a mixture of diffusion particles and transparent resin so as to scatter and diffuse the light received.

Meanwhile, in order to perform a wavelength conversion function with white light, the phosphor included in the photoexcitation layer may be made of a material that emits light having complementary relation with the incident light. In addition, the phosphor included in the photoexcitation layer may be made of a plurality of materials emitting light of different wavelengths so that the photoexcitation layer can emit white light.

Another aspect of the invention,

A phosphor and a transparent resin to absorb light emitted from the light source, a light guide plate for converting light emitted from the light source to a surface light source, and light emitted from the light guide plate to emit light having a wavelength different from that of the absorbed light. It provides a backlight unit comprising a wavelength conversion diffusion sheet having a light excitation layer formed by mixing and a light diffusion layer formed to face the light excitation layer and scatters and diffuses the received light.

In this case, it is advantageous that the light source is an LED in terms of miniaturization and economy of the backlight unit.

Preferably, the light source generates blue light, and emits white light by mixing light emitted from the light guide plate with light emitted from the light excitation layer of the diffusion sheet or light emitted from the light excitation layer of the diffusion sheet. Can be.

On the other hand, the backlight unit may be adopted both a direct type and a side type, and thus the light source may be formed on any one of the lower side, one side, and both sides of the light guide plate to provide light to the light guide plate side.

Preferably, the wavelength conversion diffusion sheet further includes a substrate layer having light transmissivity between the light excitation layer and the light diffusion layer. In this case, the substrate layer may be polyethylene terephthalate, polyethylene naphthalate, acrylic resin, or polyester. It may be made of a material selected from the group consisting of polycarbonate, polystyrene, polyolefin, cellulose acetate and synthetic resin of weather resistant vinyl chloride.

Preferably, the light diffusion layer may be formed by mixing the diffusion particles and the transparent resin.

In relation to the preferred positional relationship of the layers constituting the wavelength conversion diffusion sheet employed in the present invention, the wavelength conversion diffusion sheet may be a light diffusion layer formed on the light incident side of the light emitted from the light guide plate.

Preferably, the phosphor constituting the photoexcitation layer may be formed of a material emitting light complementary to the incident light, and the phosphor included in the photoexcitation layer may emit white light. It may be made of a plurality of types of materials that emit light of different wavelengths.

In addition, the backlight unit may further include a reflector disposed under the light guide plate to reflect light toward the light guide plate.

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

1 is a cross-sectional view of a wavelength conversion diffusion sheet according to an embodiment of the present invention.

Referring to FIG. 1, the wavelength conversion diffusion sheet 10 according to the present embodiment converts a monochromatic light source into a white light source, makes the luminance uniform according to a viewing angle, and the light diffusion layer 11 formed adjacent to each other. The light excitation layer 12 is provided and comprised.

The light diffusion layer 11 is formed by mixing a plurality of diffusion particles (shown in the form of particles) and a transparent resin, and functions to scatter and diffuse the received light. In this case, the diffusion particles may be a transparent diffusion agent such as acrylic resin, styrene resin, silicone resin, synthetic silica, glass beads, or silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ), zinc oxide (ZnO), barium sulfate ( BaSO ₄ ), calcium carbonate (CaCO ₃ ), magnesium carbonate (MgCO ₃ ), aluminum hydroxide (Al (OH) ₃ ), may be made of a white diffuser such as clay or a mixture thereof.

The photoexcited layer 12 absorbs the incident light and emits light having a wavelength different from that of the absorbed light, and is formed by mixing a phosphor (shown in the form of particles) and a transparent resin. In this case, a light source (not shown) may be provided in the direction of the light diffusion layer 11 or the light excitation layer 12 and may be incident on the light diffusion layer 11 or the light excitation layer 12. Accordingly, the diffusion sheet 10 may perform all of light diffusion, light scattering, and wavelength conversion functions, and there is no need to directly apply a phosphor to a light source such as an LED, and thus, the backlight unit employing the diffusion sheet 10 may be used. Can be expected to improve the light efficiency and reliability.

In addition, the light diffusing layer 11 and the light excitation layer 12 may adjust the thickness and the concentration, refractive index or size of the diffusion particles (in the case of the light diffusion layer) or the phosphor particles (in the case of the light excitation layer), diffusion and wavelength You can adjust the degree of conversion.

On the other hand, in order to perform the white light emitting function as described above, the phosphor included in the light excitation layer 12 is preferably made of a material that emits light in complementary relationship with the incident light. For example, when the incident light is blue light, it is preferable to employ yellow phosphor particles which are complementary with blue. As another method for performing the white light emitting function, the phosphor included in the photoexcited layer 12 may be formed of a plurality of materials emitting different wavelengths of light.

The diffusion sheet 10 may be formed by forming a light excitation layer 12 on the light diffusion layer 11 and performing high temperature compression molding.

2 is a cross-sectional view of a wavelength conversion diffusion sheet according to another embodiment of the present invention. The wavelength conversion diffusion sheet 20 according to the present embodiment is composed of a base layer 23 and a light excitation layer 22 sequentially formed on the light diffusion layer 21. The substrate layer is further included between the photoexcited layers.

Here, the description of the light diffusing layer 21 and the light excitation layer 22 is the same as in the case of the embodiment of FIG. 1, and the base layer 23 will be described. The base layer 23 may be used without limitation as long as it has a light transmitting material, and specifically, polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polyester, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weatherproof vinyl chloride Synthetic resins and the like may be employed.

On the other hand, the portion indicated by the arrow in Figure 2 shows a process in which the light emitted from the light source is diffused and converted by the diffusion sheet 20. In this embodiment, the blue light B is incident in the direction of the light diffusion layer 21, and the blue light B is diffused and scattered by the light diffusion layer 21. Thereafter, the diffused and scattered light passes through the base layer 23 and is incident on the light excitation layer 22. Subsequently, the light incident on the photoexcited layer 22 may be emitted as white light W by yellow phosphor particles having a complementary color relationship with blue. Furthermore, since the phosphor included in the photoexcited layer 22 may be employed in the form of particles, the diffusion effect of light incident on the photoexcited layer 22 may be further improved.

In the present embodiment, the light diffusion, scattering, and wavelength conversion processes when the substrate layer 23 is employed have been described. However, the light diffusion and wavelength conversion can be performed in the same manner as in the embodiment of FIG. The case where light is incident in the direction of (22) can also be considered.

In the same manner as the diffusion sheet described with reference to FIG. 1, the diffusion sheet 20 may be formed by forming a light diffusion layer 21 and a light excitation layer 22 on both sides of the substrate layer 23, respectively, and performing high temperature compression molding. Can be.

Hereinafter, a backlight unit according to another embodiment of the present invention will be described with reference to FIGS. 3 to 5.

3 and 4 are cross-sectional and exploded perspective views illustrating a backlight unit according to an embodiment of the present invention.

3 and 4, the backlight unit 300 according to the present invention has a side view, and includes a plurality of light sources 114, a substrate 112 on which the light sources 114 are mounted, and a light guide plate. 120, a reflector 140, a wavelength conversion diffusion sheet 150, and a prism sheet 151.

The light source 114 is a light emitting means for generating light when power is applied, and such a light source may be selectively employed, such as LED, fluorescent lamp. In one embodiment of the present invention for converting a single color light source into a white light source, in FIG. 4, the light source 114 shows a plurality of LEDs. However, the present invention is not limited thereto, and a fluorescent lamp, which is a linear light source, may be employed. have. In the present embodiment, the light source 114 is formed on only one side of the light guide plate 120, but the present invention is not limited thereto, and the light source 114 may be formed on both sides of the light guide plate 120 against each other. .

The light guide plate 120 is disposed on one side of the light source 114 is a hexahedral structure made of a transparent material such as PMMA to transmit light. In the present embodiment, the light guide plate 120 functions to convert the light incident from the line light source or the point light source through the edge into surface light and output the light in the vertical direction.

The reflector 140 is disposed directly below the light guide plate 120 so as to reflect the light incident on the bottom surface of the light guide plate 120 to the light exit upper surface side of the light guide plate 120 with a high light reflectance. It is provided with a reflecting sheet or a reflecting plate having.

The wavelength conversion diffusion sheet 150 employed in the present embodiment may be employed as the structure described with reference to FIGS. 1 and 2, and in this embodiment, light incident on the light guide plate 120 (not shown). ) To diffuse and convert wavelengths. A detailed description of the wavelength conversion diffusion sheet 150 is as described above with reference to FIGS. 1 and 2.

The prism sheet 151 serves to collect light emitted from the upper side of the backlight unit 300 toward the liquid crystal panel side (not shown) into the front viewing angle. In this embodiment, as shown in FIG. It is a structure laminated in layers. In this case, the prism sheet 151 should be flexible so as to transmit visible light and adhere well when mounted on the backlight unit, and the material may be polycarbonate, polyester, PMMA, PVC, acrylic polymer, or the like. Meanwhile, the diffusion sheet 150 and the prism sheet 151 may be collectively referred to as an optical sheet.

Finally, referring to Fig. 5, a backlight unit according to another embodiment of the present invention will be described. 5 is an exploded perspective view of a backlight unit according to another embodiment of the present invention.

Referring to FIG. 5, the backlight unit 500 according to the present embodiment has a direct structure, and as in the case of the side view structure described with reference to FIGS. 3 and 4, a plurality of light sources 514 and the light sources 514 are mounted. And a substrate 512, a light guide plate 520, a reflector 540, a wavelength conversion diffusion sheet 550, and a prism sheet 551. However, unlike the case where the light source of FIG. 4 is disposed on the side surface, in the present embodiment, the light source 514 is disposed below the light guide plate 520. In addition, since the light guide plate 520 for converting to a surface light source is not an essential component, the light guide plate 520 may also function as a backlight unit without a light guide plate 520.

The above-described embodiments and the accompanying drawings are merely illustrative of preferred embodiments, and the present invention is intended to be limited by the appended claims. In addition, it will be apparent to those skilled in the art that the present invention may be substituted, modified, and changed in various forms without departing from the technical spirit of the present invention described in the claims.

As described above, according to the present invention, a wavelength conversion diffusion sheet and a backlight unit using the same may be obtained by employing an optical excitation layer as a diffusion sheet and improving luminance, luminance uniformity, and color uniformity.

Claims (17)

A photoexcitation layer that absorbs the received light and emits light having a wavelength different from that of the absorbed light, wherein the phosphor and the transparent resin are mixed with each other; And And a light diffusion layer formed to face the light excitation layer and scattering and diffusing the received light. The method of claim 1, A diffusion sheet for converting wavelengths, further comprising a substrate layer having a light transmitting property between the light excitation layer and the light diffusion layer. The method of claim 2, The substrate layer is a diffusion sheet for wavelength conversion, characterized in that consisting of a material consisting of a synthetic resin of polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polyester, polycarbonate, polystyrene, polyolefin, cellulose acetate and weather-resistant vinyl chloride . The method of claim 1, The light diffusion layer is a diffusion sheet for wavelength conversion, characterized in that the diffusion particles and the transparent resin is mixed. The method of claim 1, The phosphor included in the light excitation layer is a wavelength conversion diffusion sheet, characterized in that made of a material that emits light complementary to the incident light. The method of claim 1, The phosphor included in the photoexcitation layer is a wavelength conversion diffusion sheet, characterized in that made of a plurality of materials that emit light of different wavelengths so that the light excitation layer can emit white light. A light source generating light when power is applied; A light guide plate for converting light emitted from the light source into a surface light source; And A light excitation layer formed by mixing a phosphor and a transparent resin so as to absorb light emitted from the light guide plate to emit light having a wavelength different from that of the absorbed light, and is formed to face the light excitation layer, and scatters the incident light; A wavelength conversion diffusion sheet comprising a light diffusion layer to diffuse; The backlight unit having a. The method of claim 7, wherein The light source is a backlight unit, characterized in that the LED. The method of claim 7, wherein The light source generates blue light and emits white light by mixing light emitted from the light guide plate with light emitted from the light excitation layer of the diffusion sheet or light emitted from the light excitation layer of the diffusion sheet. unit. The method of claim 7, wherein The light source is a backlight unit, characterized in that formed on any one of the lower side, one side and both sides of the light guide plate to provide light to the light guide plate side. The method of claim 7, wherein The wavelength conversion diffusion sheet further comprises a light-transmitting layer and a substrate layer having a light transmitting property to the light diffusion layer. The method of claim 11, The base layer is a backlight unit, characterized in that made of a material selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polyester, polycarbonate, polystyrene, polyolefin, cellulose acetate and synthetic resin of weather resistant vinyl chloride. The method of claim 7, wherein The light diffusion layer is a backlight unit, characterized in that the diffusion particles and the transparent resin is mixed. The method of claim 7, wherein And the light diffusion layer included in the wavelength conversion diffusion sheet is formed on a light incident side of light emitted from the light guide plate. The method of claim 7, wherein The phosphor included in the light excitation layer is a backlight unit, characterized in that made of a material that emits light complementary to the incident light. The method of claim 7, wherein The phosphor included in the photoexcited layer is a backlight unit, characterized in that made of a plurality of materials that emit light of different wavelengths so that the photoexcited layer can emit white light. The method of claim 7, wherein And a reflector disposed under the light guide plate to reflect light toward the light guide plate.

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